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Vitamin E

Vitamin E

Description

Vitamin E is an antioxidant responsible for proper functioning of the immune system and for maintaining healthy eyes and skin. It is actually a group of fat soluble compounds known as tocopherols (i.e., alpha tocopherol and gamma tocopherol). Gamma tocopherol accounts for approximately 75% of dietary vitamin E. Vitamin E rich foods include nuts, cereals, beans, eggs, cold-pressed oils, and assorted fruits and vegetables. Because vitamin E is a fat soluble vitamin, it requires the presence of fat for proper absorption. Daily dietary intake of the recommended daily allowance (RDA) of vitamin E is recommended for optimum health.

Vitamin E is absorbed by the gastrointestinal system and stored in tissues and organs throughout the body. Certain health conditions may cause vitamin E depletion, including liver disease, celiac disease , and cystic fibrosis. Patients with end-stage renal disease (kidney failure) who are undergoing chronic dialysis treatment may be at risk for vitamin E deficiency. These patients frequently receive intravenous infusions of iron supplements, which can act against vitamin E.

Vitamin E deficiency can cause fatigue , concentration problems, weakened immune system, anemia , and low thyroid levels. It may also cause vision problems and irritability. Low serum (or blood) levels of vitamin E have also been linked to major depression .

General use

Vitamin E is necessary for optimal immune system functioning, healthy eyes, and cell protection throughout the body. It has also been linked to the prevention of a number of diseases. The therapeutic benefits of vitamin E include:

  • Cancer prevention and treatment. Vitamin E is a known antioxidant, and has been associated with a reduced risk of gastrointestinal, cervical, prostate, lung, and possibly breast cancer . In addition to its role as a cancer preventive, vitamin E is being studied as a cancer treatment. It has been shown to inhibit the growth of prostate tumors and to induce apoptosis (cell self-destruction) in cancer cells. Vitamin E is also being investigated as an adjunctive treatment for cancer patients undergoing radiation therapy; it is thought that high doses of dietary antioxidants may increase the efficacy of the radiation treatment while protecting healthy cells against damage.
  • Immune system protection. Various studies have shown that vitamin E supplementation, particularly in elderly patients, boosts immune system function. Older patients have demonstrated improved immune response, increased resistance to infections , and higher antibody production. Vitamin E has also been used with some success to slow disease progression in HIV-positive patients.
  • Eye disease prevention. Clinical studies on vitamin E have shown that supplementation significantly reduces the risk for cataracts and for macular degeneration , particularly among women.
  • Memory loss prevention. Vitamin E deficiency has been linked to poor performance on memory tests in some elderly individuals.
  • Alzheimer's disease (AD) treatment. In a study performed at Columbia University, researchers found that Alzheimer's patients who took daily supplements of vitamin E maintained normal functioning longer than patients who took a placebo. In 2002, a group of Dutch epidemiologists reported on a much larger populationbased study conducted in the Netherlands between 1990 and 1993, with follow-up examinations in 1994 and 1999. The study confirmed the findings of the Columbia researchers, that high dietary intake of vitamin E lowers the risk of developing AD.
  • Liver disease treatment. Vitamin E may protect the liver against disease.
  • Diabetes treatment. Vitamin E may help diabetic patients process insulin more effectively. It has also been found to be effective in the treatment of diabetic neuropathy, a family of nerve disorders caused by diabetes. Vitamin E appears to reduce the symptoms of diabetic neuropathy and to improve the speed of transmission of nerve impulses.
  • Pain relief. Vitamin E acts as both an anti-inflammatory and analgesic (or pain reliever). Studies have indicated it may be useful for treatment of arthritis pain in some individuals.
  • Parkinson's disease prevention. High doses of vitamin E intake was associated with a lowered risk of developing Parkinson's disease in one 1997 Dutch study.
  • Tardive dyskinesia treatment. Individuals who take neuroleptic drugs for schizophrenia or other disorders may suffer from a side effect known as tardive dyskinesia, in which they experience involuntary muscle contractions or twitches. Vitamin E supplementation may lessen or eliminate this side effect in some individuals.
  • Porphyria treatment. Vitamin E has been found to be beneficial in treating patients with porphyria, a group of disorders characterized by abnormalities in the metabolism of blood pigments, by lowering the level of excretion of these blood pigments in the urine.

Other benefits of vitamin E are less clear cut, and have been called into question with conflicting study results or because of a lack of controlled studies to support them. These include:

  • Heart disease prevention. A number of epidemiological studies have indicated that vitamin E may prevent heart disease by lowering total blood cholesterol levels and preventing oxidation of LDL cholesterol. However, a large, controlled study known as the Heart Outcomes Prevention Evaluation (HOPE) published in early 2000 indicates that vitamin E does not have any preventative effects against heart disease. The study followed 9,500 individuals who were considered to be at a high risk for heart disease. Half the individuals were randomly chosen to receive vitamin E supplementation, and the other half of the study population received a placebo. After five years, there was no measurable difference in heart attacks and heart disease between the two patient populations. Still, vitamin E may still hold some hope for heart disease prevention. It is possible that a longer-term study beyond the five years of the HOPE study may demonstrate some heart protective benefits of vitamin E consumption. It is also possible that while the high-risk patient population that was used for the HOPE study did not benefit from vitamin E, an average-risk patient population might still benefit from supplementation. It is also possible that vitamin E needs the presence of another vitamin or nutrient substance to protect against heart disease. Further large, controlled, and long-term clinical studies are necessary to answer these questions.
  • Skin care. Vitamin E is thought to increase an individual's tolerance to UV rays when taken as a supplement in conjunction with vitamin C . Vitamin E has also been touted as a treatment to promote faster healing of flesh wounds . While its anti-inflammatory and analgesic properties may have some benefits in reducing swelling and relieving discomfort in a wound, some dermatologists dispute the claims of faster healing, and there are no large controlled studies to support this claim.
  • Hot flashes . In a small study conducted at the Mayo Clinic, researchers found that breast cancer survivors who suffered from hot flashes experienced a decrease in hot flashes after taking vitamin E supplementation.
  • Muscle maintenance and repair. Recent research has demonstrated that the antioxidative properties of vitamin E may prevent damage to tissues caused by heavy endurance exercises. In addition, vitamin E supplementation given prior to surgical procedures on muscle and joint tissues has been shown to limit reperfusion injury (muscle damage that occurs when blood flow is stopped, and then started again to tissues or organs).
  • Fertility. Vitamin E has been shown to improve sperm function in animal studies, and may have a similar effect in human males. Further studies are needed to establish the efficacy of vitamin E as a treatment for male infertility ; as of 2002, its role in such treatment is still controversial.

Preparations

The U.S. recommended dietary allowance (RDA) of the alpha-tocopherol formulation of vitamin E is as follows:

  • men: 10 mg or 15 IU
  • women: 8 mg or 12 IU
  • pregnant women: 10 mg or 15 IU
  • lactating women: 12 mg or 18 IU

In April 2000, the National Academy of Sciences recommended changing the RDA for vitamin E to 22 international units (IUs), with an upper limit (UL), or maximum daily dose, of 1500 IUs. Daily values for the vitamin as recommended by the U.S. Food and Drug Administration, the values listed on food and beverage labeling, remain at 30 IUs for both men and women age four and older.

Many nuts, vegetable-based oils, fruits, and vegetables contain vitamin E. Foods rich in vitamin E include wheat germ oil (26.2 mg/tbsp), wheat germ cereal (19.5 mg/cup), peanuts (6.32 mg/half cup), soybeans (3.19 mg/cup), corn oil (2.87/tbsp), avocado (2.69 mg), and olive oil (1.68 mg/tbsp.). Grapes, peaches, broccoli, Brussels sprouts, eggs, tomatoes, and blackberries are also good sources of vitamin E. Fresh, raw foods contain the highest levels of the vitamin. Both heat and light can reduce vitamin and mineral potency in fresh foods, so overcooking and improper storage should be avoided. Sliced and chopped foods have more of their surface exposed to light, therefore keeping vegetables and fruits whole may also help to maintain full vitamin potency.

For individuals considered at risk for vitamin E deficiency, or those with an inadequate dietary intake, vitamin E supplements are available in a variety of different forms, including pills, capsules, powders, and liquids for oral ingestion. For topical use, vitamin E is available in ointments, creams, lotions, and oils. Vitamin E is also available commercially as one ingredient of a multivitamin formula.

The recommended daily dosage of vitamin E varies by individual need and by the amount of polyunsaturated fats an individual consumes. The more polyunsaturated fats in the diet, the higher the recommended dose of vitamin E, because vitamin E helps to prevent the oxidizing effects of these fats. Because vitamin E is fat soluble, supplements should always be taken with food.

Supplements are also available in either natural or synthetic formulations. Natural forms are extracted from wheat germ oil and other vitamin E food sources, and synthetic forms are extracted from petroleum oils. Natural formulas can be identified by a d prefix on the name of the vitamin (i.e., d-alpha-tocopherol).

Precautions

Overdoses of vitamin E (over 536 mg) can cause nausea, diarrhea, headache , abdominal pain, bleeding, high blood pressure, fatigue, and weakened immune system function.

Patients with rheumatic heart disease, iron deficiency anemia, hypertension , or thyroid dysfunction should consult their healthcare provider before starting vitamin E supplementation, as vitamin E may have a negative impact on these conditions.

Side effects

Vitamin E is well-tolerated, and side effects are rare. However, in some individuals who are vitamin K deficient, vitamin E may increase the risk for hemorrhage or bleeding. In some cases, side effects may be decreased or eliminated by adjusting the dosage of vitamin E and vitamin K.

Although the reasons are not yet clear, high intake of vitamin E has been associated with a statistically significant increased risk of breast cancer in men.

Vitamin E ointments, oils, or creams may trigger an allergic reaction known as contact dermatitis . Individuals who are considering using topical vitamin E preparations for the first time, or who are switching the type of vitamin E product they use, should perform a skin patch test to check for skin sensitivity to the substance. A small, dime sized drop of the product should be applied to a small patch of skin inside the elbow or wrist. The skin patch should be monitored for 24 hours to ensure no excessive redness, irritation, or rash occurs. If a reaction does occur, it may be in response to other ingredients in the topical preparation, and the test can be repeated with a different vitamin E formulation. Individuals who experience a severe reaction to a skin patch test of vitamin E are advised not to use the product topically. A dermatologist or other healthcare professional may be able to recommend a suitable alternative.

Interactions

Individuals who take anticoagulant (blood thinning) or anticonvulsant medications should consult their healthcare provider before starting vitamin E supplementation. Vitamin E can alter the efficacy of these drugs.

It is important for persons taking supplemental vitamin E to tell their surgeon if they are scheduled for an operation. Vitamin E may interact with some of the medications given prior to or during surgery; it has also been shown to increase bleeding time if the patient is taking such other herbal preparations as feverfew or gingko biloba.

Non-heme, inorganic iron supplements destroy vitamin E, so individuals taking iron supplements should space out their doses (e.g., iron in the morning and vitamin E in the evening).

Large doses of vitamin A can decrease the absorption of vitamin E, so dosage adjustments may be necessary in individuals supplementing with both vitamins.

Alcohol and mineral oil can also reduce vitamin E absorption, and these substances should be avoided if possible in vitamin E deficient individuals.

Resources

BOOKS

Reavley, Nocola. The New Encyclopedia of Vitamins, Minerals, Supplements, and Herbs. New York: M. Evans & Company, 1998.

PERIODICALS

Bolle, P., M. G. Evandri, and L. Saso. "The Controversial Efficacy of Vitamin E for Human Male Infertility." Contraception 65 (April 2002): 313-315.

Bonner, L. T., and E. R. Peskind. "Pharmacologic Treatments of Dementia." Medical Clinics of North America 86 (May 2002): 657-674.

Collins, S. C., and R. G. Dufresne Jr. "Dietary Supplements in the Setting of Mohs Surgery." Dermatologic Surgery 28 (June 2002): 447-452.

Engelhart, M. J., M. I. Geerlings, A. Ruitenberg, et al. "Dietary Intake of Antioxidants and Risk of Alzheimer's Disease." Journal of the American Medical Association 287 (June 26, 2002): 3261-3263.

Johnson, K. C., S. Pan, and Y. Mao. "Risk Factors for Male Breast Cancer in Canada, 1994-1998." European Journal of Cancer Prevention 11 (June 2002): 253-263.

Pinelli, A., S. Trivulzio, L. Tomasoni, et al. "High-Dose Vitamin E Lowers Urine Porphyrin Levels in Patients Affected by Porphyria Cutanea Tarda." Pharmacological Research 45 (April 2002): 355-359.

Prasad, K. N., W. C. Cole, B. Kumar, and K. Che Prasad. "Pros and Cons of Antioxidant Use During Radiation Therapy." Cancer Treatment Review 28 (April 2002): 79-91.

Sytze Van Dam, P. "Oxidative Stress and Diabetic Neuropathy: Pathophysiological Mechanisms and Treatment Perspectives." Diabetes/Metabolism Research and Reviews 18 (May-June 2002): 176-184.

"Vitamin E: E for Exaggerated?" Harvard Health Letter 25, no. 5 (March 2000):6(3p).

Yu, A., P. Somasundar, A. Balsubramaniam, et al. "Vitamin E and the Y4 Agonist BA-129 Decrease Prostate Cancer Growth and Production of Vascular Endothelial Growth Factor." Journal of Surgical Research 105 (June 1, 2002): 65-68.

ORGANIZATIONS

American Dietetic Association. 216 West Jackson Blvd., Chicago, IL 60606. (312) 899-0040. <www.eatright.org>.

United States Department of Agriculture. Center for Nutrition Policy and Promotion. 1120 20th Street NW, Suite 200, North Lobby, Washington, D.C. 20036. (202) 418-2312. <www.usda.gov/cnpp>.

United States Food and Drug Administration (FDA). 5600 Fishers Lane, Rockville, MD 20857. (888) 463-6332. <www.fda.gov>.

Paula Ford-Martin

Rebecca J. Frey, PhD

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Vitamin E Deficiency

Vitamin E Deficiency

Definition

Vitamin E deficiency is a very rare problem that results in damage to nerves. When vitamin E deficiency does occur, it strikes people with diseases that prevent the absorption of dietary fats and fat-soluble nutrients. Since vitamin E is a fat-soluble vitamin, it has some of the properties of fat.

Description

The recommended dietary allowance (RDA) for vitamin E is 10 mg/day for the adult man, 10 mg/day for the adult woman, and 3 mg/day for the infant. Vitamin E occurs in foods in a variety of related forms. The most potent and useful form of vitamin E is called alpha-tocopherol. The best sources of vitamin E are vegetable oils, such as corn oil, soy oil, and peanut oil. Animal fats, such as butter and lard, contain lower levels of the vitamin. Corn oil contains about 16 mg of alpha-tocopherol per 100 g oil. Wheat-germ oil contains 120 mg alpha-tocopherol per 100 g oil. Fish, eggs, and beef contain relatively low levels of the vitamin, with about 1 mg per 100 g food.

Vitamin E seems to have only one function in the body: the prevention of the natural and continual process of deterioration of all body tissues. This deterioration is provoked by a number of causes; one of these is toxic oxygen. During the body's metabolism of atmospheric oxygen, toxic oxygen is produced continuously in the body by the formation of by-products. These toxic by-products include hydrogen peroxide, superoxide, and hypochlorite.

Hypochlorite is a natural product, produced by cells of the immune system. It is also the active component of bleach. Once formed, toxic oxygen can damage various parts of the body, such as the membranes which form the boundaries of every cell. Vitamin E serves the body in protecting membranes from toxic oxygen damage. In contrast, vitamin C serves to protect the aqueous, or watery, regions of the cell from toxic oxygen damage. The membranes that are most sensitive to toxic oxygen damage are the membranes of nerves; therefore, the main symptom of vitamin E deficiency is damage to the nervous system.

Causes and symptoms

As mentioned, when vitamin E deficiency occurs, it strikes people with diseases that prevent the absorption of dietary fats and fat-soluble nutrients. These diseases include cystic fibrosis, pancreatitis, and cholestasis (bile-flow obstruction). Bile salts, produced in the liver, are required for the absorption of fats. Cholestasis causes a decrease in the formation of bile salts and the consequent failure of the body to absorb dietary fats. For this reason, this disease may result in vitamin E deficiency. Premature infants may be at risk for vitamin E deficiency because they may be born with low tissue levels of the vitamin, and because they have a poorly developed capacity for absorbing dietary fats. Infants suffering from fat-malabsorption diseases can develop symptoms of vitamin E deficiency by age two. In adults, the onset of a fat-malabsorption disease can provoke vitamin E deficiency after a longer period, as an example, ten years.

Patients with colorectal cancer caused by the socalled Ki-ras mutation have also been shown to absorb less vitamin E from their diet than either normal control subjects or cancer patients without the mutation. The relationship between genetic mutations and dietary factors requires more intensive study.

Vitamin E deficiency in humans results in ataxia (poor muscle coordination with shaky movements), decreased sensation to vibration, lack of reflexes, and paralysis of eye muscles. One particularly severe symptom of vitamin E deficiency is the inability to walk.

Another symptom of early vitamin E deficiency in children with cystic fibrosis is a decline in cognitive function, which results in difficulty with reading and falling behind in other intellectual skills during the elementary school years. Researchers have urged the introduction of neonatal screening in order to offset the potential effects of early vitamin E deficiency.

More recently, the suggestion has been made that vitamin E deficiency may be involved in the development of partial open-angle glaucoma (POAG), an eye disorder whose causes are not fully understood as of the early 2000s. The possibility that POAG is a vitamin-deficiency disorder, however, needs further research.

Diagnosis

Vitamin E status is measured by assessment of the content of alpha-tocopherol in the blood plasma, using a method called high-pressure liquid chromatography. Blood plasma levels of alpha-tocopherol that are 5.0 mg/l, or above, indicate normal vitamin E status; levels below 5.0 mg/l indicate vitamin E deficiency.

Treatment

Vitamin E deficiency that occurs with cholestatic liver disease or other malabsorption syndromes can be treated with weekly injections of 100 mg alpha-tocopherol that may continue for six months. Vitamin E deficiency in premature infants may require treatment for only a few weeks.

Prognosis

The prognosis for correcting the neurological symptoms of vitamin E deficiency is fair to excellent.

Prevention

The prevention of vitamin E deficiency should not be a concern for most people, since the vitamin is found in a wide variety of foods. Attention has been given to the theory that vitamin E serves to protect against cancer and atherosclerosis. The evidence that normal levels of vitamin E protect against atherosclerosis is fairly convincing. However, there is little or no proof that vitamin E intake, above and beyond the recommended daily allowance (RDA), can prevent cancer or atherosclerosis.

Resources

BOOKS

Beers, Mark H., MD, and Robert Berkow, MD, editors. "Vitamin E Deficiency." Section 7, Chapter 86. In The Merck Manual of Diagnosis and Therapy. Whitehouse Station, NJ: Merck Research Laboratories, 2004.

PERIODICALS

Koscik, R. L., P. M. Farrell, M. R. Kosorok, et al. "Cognitive Function of Children with Cystic Fibrosis: Deleterious Effect of Early Malnutrition." Pediatrics 113 (June 2004): 1549-1558.

Laso, N., S. Mas, M. Jose Lafuente, et al. "Decrease in Specific Micronutrient Intake in Colorectal Cancer Patients with Tumors Presenting Ki-ras Mutation." Anticancer Research 24 (May-June 2004): 2011-2020.

Veach, J. "Functional Dichotomy: Glutathione and Vitamin E in Homeostasis Relevant to Primary Open-Angle Glaucoma." British Journal of Nutrition 91 (June 2004): 809-829.

KEY TERMS

Fat-soluble vitamin Fat-soluble vitamins can be dissolved in oil or in melted fat.

Recommended dietary allowance (RDA) The quantity of a given nutrient in the diet that is required to maintain good health in people. RDAs are established by the Food and Nutrition Board of the National Academy of Sciences, and may be revised every few years. A separate RDA value exists for each nutrient. The RDA values refer to the amount of nutrient expected to maintain good health in people. The actual amounts of each nutrient required to maintain good health in specific individuals differ from person to person.

Toxic oxygen Oxygen is required for life, as it is needed for energy production. When oxygen is used by the body, most of it is converted to water. However, a small fraction of the oxygen breathed is converted to toxic oxygen. The body uses several different processes for preventing and repairing toxic-oxygen damage. One of these processes involves vitamin E.

Water-soluble vitamins Water-soluble vitamins can be dissolved in water or juice.

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Vitamin E

Vitamin E

Vitamin E was discovered in 1922 by Herbert M. Evans and K. S. Bishop. The researchers found that laboratory rats failed to reproduce when lard was their only source of food fat. According to the researchers, there was a compound in both wheat germ and lettuce that corrected the problem.

For a time, the unknown component was termed the "anti-sterility factor." In 1925 Evans decided that the component should be renamed vitamin E since the last vitamin to be discovered was vitamin D.

The new vitamin was fat-soluble. Studies by Evans and his coworker Gladys A. Emerson (1903-) showed that vitamin E deficiency caused two different problems. It caused reproductive problems in both sexes of small laboratory animals. It also caused a muscle dystrophy in many species of animals. But for almost three decades, investigators were not certain whether vitamin E had any effect on humans.

Vitamin E Isolated

Evans and Emerson isolated vitamin E from wheat germ oil, corn oil, and cotton seed oil in 1936. In 1938 it was synthesized by Paul Karrer (1889-1971) and his co-workers. The investigators decided the vitamin's biochemical function was primarily a protective one. Its purpose is to help prevent unsaturated fatty acids from combining with oxygen. When the acids and oxygen do combine, tissues break down. Other antioxidants include vitamin C and the trace element selenium.

At first, vitamin E was believed to regulate tissue-damaging oxidation almost entirely in animals. But nutritional surveys in the 1940s and 1950s revealed otherwise. Premature infants and patients with malabsorption illnesses were found to have low levels of blood tocopherol. Those same surveys also showed they had other blood irregularities as well. In 1968, vitamin E was finally recognized as an essential nutrient for humans.

Other Functions of the Vitamin

Vitamin E is believed to help maintain the structure of muscle tissue and various components of the reproductive system, vascular system, and nervous system. Even with this knowledge, there may be other functions the vitamin performs that researchers are not aware of. There is little evidence to suggest, however, that vitamin E supplements can help repair existing damage.

[See also Vitamin ]

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vitamin E

vitamin E Generic descriptor for a group of fat‐soluble compounds essential for reproduction in animals. Essential for human beings (not for reproduction, so far as is known) but rarely, if ever, deficient in the diet. Two main groups of compounds have vitamin E activity: the tocopherols and the tocotrienols; there are 4 isomers of each: α‐, β‐, γ, and δ‐tocopherols and α‐, β‐, γ, and δ‐tocotrienols, with differing vitamin potencies.

Vitamin E functions primarily as an antioxidant in cell membranes, protecting unsaturated fatty acids from oxidative damage.

The vitamin E content of foods is expressed as mg α‐tocopherol equivalent (based on the different potency of the different vitamers). Vegetables, seeds, and most vegetable oils are good sources. In the UK and the EU an adequate intake is 0.4 mg/g dietary polyunsaturated fatty acid intake; the US/Canadian RDA is 15 mg/day. The obsolete international unit of vitamin E activity was equal to 1 mg of synthetic α‐tocopherol; on this basis natural‐source α‐tocopherol is 1.49 iu/mg.

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vitamin E

vitamin E (tocopherol) A fat-soluble vitamin consisting of several closely related compounds, deficiency of which leads to a range of disorders in different species, including muscular dystrophy, liver damage, and infertility. Good sources are cereal grains and green vegetables. Vitamin E prevents the oxidation of unsaturated fatty acids in cell membranes, so maintaining their structure (see antioxidants).

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vitamin E

vitamin E n. any of a group of chemically related fat-soluble compounds (tocopherols and tocotrienols) that have antioxidant properties and are thought to stabilize cell membranes. Good sources of the vitamin are vegetable oils, eggs, butter, and wholemeal cereals. It is fairly widely distributed in the diet and a deficiency is therefore unlikely.

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vitamin E

vi·ta·min E • n. another term for tocopherol.

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vitamin E

vitamin E See TOCOPHEROL.

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Vitamin E

Vitamin E

Description

Vitamin E is an antioxidant responsible for proper functioning of the immune system and for maintaining healthy eyes and skin. It is actually a group of fat soluble compounds known as tocopherols (i.e., alpha tocopherol and gamma tocopherol). Gamma tocopherol accounts for approximately 75% of dietary vitamin E. Vitamin E rich foods include nuts, cereals, beans, eggs, cold-pressed oils, and assorted fruits and vegetables. Because vitamin E is a fat soluble vitamin, it requires the presence of fat for proper absorption. Daily dietary intake of the recommended daily allowance (RDA) of vitamin E is recommended for optimum health.

Vitamin E is absorbed by the gastrointestinal system and stored in tissues and organs throughout the body. Certain health conditions may cause vitamin E depletion, including liver disease, celiac disease, and cystic fibrosis. Patients with end-stage renal disease(kidney failure) who are undergoing chronic dialysis treatment may be at risk for vitamin E deficiency. These patients frequently receive intravenous infusions of iron supplements which can act against vitamin E.

Vitamin E deficiency can cause fatigue, concentration problems, weakened immune system, anemia, and low thyroid levels. It may also cause vision problems and irritability. Low serum (or blood ) levels of vitamin E have also been linked to major depression.

General use

Vitamin E is necessary for optimal immune system functioning, healthy eyes, and cell protection throughout the body. It has also been linked to the prevention of a number of diseases. The therapeutic benefits of vitamin E include:

  • Cancer prevention. Vitamin E is a known antioxidant, and has been associated with a reduced risk of gastrointestinal, cervical, prostate, lung, and possibly breast cancer.
  • Immune system protection. Various studies have shown that vitamin E supplementation, particularly in elderly patients, boosts immune system function. Older patients have demonstrated improved immune response, increased resistance to infections, and higher antibody production. Vitamin E has also been used with some success to slow disease progression in HIV-positive patients.
  • Eye disease prevention. Clinical studies on vitamin E have shown that supplementation significantly reduces the risk for cataracts and for macular degeneration, particularly among women.
  • Memory loss prevention. Vitamin E deficiency has been linked to poor performance on memory tests in some elderly individuals.
  • Alzheimer's disease treatment. In a study performed at Columbia University, researchers found that Alzheimer's patients who took daily supplements of vitamin E maintained normal functioning longer than patients who took a placebo.
  • Liver disease treatment. Vitamin E may protect the liver against disease.
  • Diabetes treatment. Vitamin E may help diabetic patients process insulin more effectively.
  • Pain relief. Vitamin E acts as both an anti-inflammatory and analgesic (or pain reliever). Studies have indicated it may be useful for treatment of arthritis pain in some individuals.
  • Parkinson's disease prevention. High doses of vitamin E intake was associated with a lowered risk of developing Parkinson's disease in one 1997 Dutch study.
  • Tardive dyskinesia treatment. Individuals who take neuroleptic drugs for schizophrenia or other disorders may suffer from a side effect known as tardive dyskinesia, in which they experience involuntary muscle contractions or twitches. Vitamin E supplementation may lessen or eliminate this side effect in some individuals.

Other benefits of vitamin E are less clear cut, and have been called into question with conflicting study results or because of a lack of controlled studies to support them. These include:

  • Heart disease prevention. A number of epidemiological studies have indicated that vitamin E may prevent heart disease by lowering total blood cholesterol levels and preventing oxidation of LDL cholesterol. However, a large, controlled study known as the Heart Outcomes Prevention Evaluation (HOPE) published in early 2000 indicates that vitamin E does not have any preventative effects against heart disease. The study followed 9,500 individuals who were considered to be at a high risk for heart disease. Half the individuals were randomly chosen to receive vitamin E supplementation, and the other half of the study population received a placebo. After five years, there was no measurable difference in heart attacks and heart disease between the two patient populations. Still, vitamin E may still hold some hope for heart disease prevention. It is possible that a longer-term study beyond the five years of the HOPE study may demonstrate some heart protective benefits of vitamin E consumption. It is also possible that while the high-risk patient population that was used for the HOPE study did not benefit from vitamin E, an average-risk patient population might still benefit from supplementation. It is also possible that vitamin E needs the presence of another vitamin or nutrient substance to protect against heart disease. Further large, controlled, and long-term clinical studies are necessary to answer these questions.
  • Skin care. Vitamin E is thought to increase an individual's tolerance to UV rays when taken as a supplement in conjunction with vitamin C. Vitamin E has also been touted as a treatment to promote faster healing of flesh wounds. While its anti-inflammatory and analgesic properties may have some benefits in reducing swelling and relieving discomfort in a wound, some dermatologists dispute the claims of faster healing, and there are no large controlled studies to support this claim.
  • Hot flashes. In a small study conducted at the Mayo Clinic, researchers found that breast cancer survivors who suffered from hot flashes experienced a decrease in those hot flashes after taking vitamin E supplementation.
  • Muscle maintenance and repair. Recent research has demonstrated that the antioxidative properties of vitamin E may prevent damage to tissues caused by heavy endurance exercises. In addition, vitamin E supplementation given prior to surgical procedures on muscle and joint tissues has been shown to limit reperfusion injury (muscle damage which occurs when blood flow is stopped, and then started again to tissues or organs).
  • Fertility. Vitamin E has been shown to improve sperm function in animal studies, and may have a similar effect in human males. Further studies are needed to establish the efficacy of vitamin E as a treatment for male infertility.

Preparations

The U.S. recommended dietary allowance (RDA) of the alpha-tocopherol formulation of vitamin E is as follows:

  • men: 10 mg or 15 IU
  • women: 8 mg or 12 IU
  • pregnant women: 10 mg or 15 IU
  • lactating women: 12 mg or 18 IU

In April 2000, the National Academy of Sciences recommended changing the RDA for vitamin E to 22 international units (IUs), with an upper limit (UL), or maximum daily dose, of 1,500 IUs. Daily values for the vitamin as recommended by the U.S. Food and Drug Administration, the values listed on food and beverage labeling, remain at 30 IUs for both men and women age four and older.

Many nuts, vegetable-based oils, fruits, and vegetables contain vitamin E. Foods rich in vitamin E include wheat germ oil (26.2 mg/tbsp), wheat germ cereal (19.5 mg/cup), peanuts (6.32 mg/half cup), soy beans (3.19 mg/cup), corn oil (2.87 mg/tbsp), avocado(2.69 mg), and olive oil (1.68 mg/tbsp). Grapes, peaches, broccoli, Brussels sprouts, eggs, tomatoes, and blackberries are also good sources of vitamin E. Fresh, raw foods contain the highest levels of the vitamin. Both heat and light can reduce vitamin and mineral potency in fresh foods, so overcooking and improper storage should be avoided. Sliced and chopped foods have more of their surface exposed to light, therefore keeping vegetables and fruits whole may also help to maintain full vitamin potency.

For individuals considered at risk for vitamin E deficiency, or those with an inadequate dietary intake, vitamin E supplements are available in a variety of different forms, including pills, capsules, powders, and liquids for oral ingestion. For topical use, vitamin E is available in ointments, creams, lotions, and oils. Vitamin E is also available commercially as one ingredient of a multivitamin formula.

The recommended daily dosage of vitamin E varies by individual need and by the amount of polyunsaturated fats an individual consumes. The more polyunsaturated fats in the diet, the higher the recommended dose of vitamin E, because vitamin E helps to prevent the oxidizing effects of these fats. Because vitamin E is fat soluble, supplements should always be taken with food.

Supplements are also available in either natural or synthetic formulations. Natural forms are extracted from wheat germ oil and other vitamin E food sources, and synthetic forms are extracted from petroleum oils. Natural formulas can be identified by a d prefix on the name of the vitamin (i.e., d-alpha-tocopherol).

Precautions

Overdoses of vitamin E (over 536 mg) can cause nausea, diarrhea, headache, abdominal pain, bleeding, high blood pressure, fatigue, and weakened immune system function.

Patients with rheumatic heart disease, iron deficiency anemia, hypertension, or thyroid dysfunction should consult their healthcare provider before starting vitamin E supplementation, as vitamin E may have a negative impact on these conditions.

Side effects

Vitamin E is well-tolerated, and side effects are rare. However, in some individuals who are vitamin K deficient, vitamin E may increase the risk for hemorrhage or bleeding. In some cases, side effects may be decreased or eliminated by adjusting the dosage of vitamin E and vitamin K.

Vitamin E ointments, oils, or creams may trigger an allergic reaction known as contact dermatitis. Individuals who are considering using topical vitamin E preparations for the first time, or who are switching the type of vitamin E product they use, should perform a skin patch test to check for skin sensitivity to the substance. A small, dime sized drop of the product should be applied to a small patch of skin inside the elbow or wrist. The skin patch should be monitored for 24 hours to ensure no excessive redness, irritation, or rash occurs. If a reaction does occur, it may be in response to other ingredients in the topical preparation, and the test can be repeated with a different vitamin E formulation. Individuals who experience a severe reaction to a skin patch test of vitamin E are advised not to use the product topically. A dermatologist or other healthcare professional may be able to recommend a suitable alternative.

Interactions

Individuals who take anticoagulant (blood thinning) or anticonvulsant medications should consult their healthcare provider before starting vitamin E supplementation. Vitamin E can alter the efficacy of these drugs.

Non-heme, inorganic iron supplements destroy vitamin E, so individuals taking iron supplements should space out their doses (e.g., iron in the morning and vitamin E in the evening).

Large doses of vitamin A can decrease the absorption of vitamin E, so dosage adjustments may be necessary in individuals supplementing with both vitamins.

Alcohol and mineral oil can also reduce vitamin E absorption, and these substances should be avoided if possible in vitamin E deficient individuals.

KEY TERMS

Antioxidants— Enzymes which bind with free radicals to neutralize their harmful effects.

Contact dermatitis Inflammation, redness, and irritation of the skin caused by an irritating substance.

Epidemiological study— A study which analyzes health events and trends in particular patient populations.

Free radicals— Reactive molecules created during cell metabolism that can cause tissue and cell damage like that which occurs in aging and with disease processes such as cancer.

Macular degeneration— Degeneration, or break-down, of the retina that can lead to partial or total blindness.

Non-heme iron— Dietary or supplemental iron that is less efficiently absorbed by the body than heme iron (ferrous iron).

Reperfusion— The reintroduction of blood flow to organs or tissues after blood flow has been stopped for surgical procedures.

Vitamin A— An essential vitamin found in liver, orange and yellow vegetables, milk, and eggs that is critical for proper growth and development.

Vitamin K A fat-soluble vitamin responsible for blood clotting, bone metabolism, and proper kidney function.

Resources

BOOKS

Reavley, Nocola. The New Encyclopedia of Vitamins, Minerals, Supplements, and Herbs. New York: M. Evans & Company, 1998.

PERIODICALS

"Vitamin E: E for Exaggerated?" Harvard Health Letter 25, no. 5 (March 2000): 6.

ORGANIZATIONS

United States Department of Agriculture. Center for Nutrition Policy and Promotion. 1120 20th Street NW, Suite 200, North Lobby, Washington, D.C. 20036. (202) 418-2312. 〈http://www.usda.gov/cnpp/〉.

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Vitamin E

Vitamin E

Definition

Purpose

Description

Precautions

Interactions

Complications

Resources

Definition

Vitamin E is a fat-soluble organic compound that the body needs to remain healthy. Humans cannot make vitamin E, so they must get it from foods in their diet. Vitamin E comes in eight forms. The most biologically active form in humans is alpha-toco-pherol. Most vitamin E in dietary supplements is synthetically manufactured alpha-tocopherol.

Purpose

Vitamin E is one of the more poorly understood and controversial vitamins. Its exact functions are not completely clear. Vitamin E is an antioxidant. Antioxidants help protect the body against damage caused by free radicals. Free radicals are formed during normal metabolic processes. The quantity of free radicals in the body may also be increased by exposure to environmental toxins, ultraviolet light, and radiation. Free radicals have a strong tendency to react with and damage other compounds, especially those in DNA (genetic material) and certain fats (lipids) in cell membranes. Antioxidants prevent this damage by reacting with free radicals to neutralneutralize

Vitamin E

Age Recommended Dietary Allowance Tolerable Upper Intake Level
Children 0–6 mos.6.0 IU (AI)4 mg (AI)Not established
Children 7–12 mos.7.5 IU (AI)5 mg (AI)Not established
Children 1–3 yrs.9.0 IU6 mg300 IU200 mg
Children 4–8 yrs.10.5 IU7 mg450 IU300 mg
Children 9–13 yrs.16.5 IU11 mg900 IU600 mg
Children 14–18 yrs.22.5 IU15 mg1,200 IU800 mg
Adult 19≥ yrs.22.5 IU15 mg1,500 IU1,000 mg
Pregnant women22.5 IU15 mg1,500 IU1,000 mg
Breastfeeding women28.5 IU19 mg1,500 IU1,000 mg
Food Vitamin E (IU) Vitamin E (mg)
Wheat germ oil, 1 tbsp.30.520.3
Almonds, roasted, 1 oz.117.4
Sunflower oil, 1 tbsp.8.55.6
Hazelnuts, roasted, 1 oz.6.54.3
Peanut butter, fortified, 1 oz.64.2
Safflower oil, 1 tbsp.64.6
Avocado, 1 med.53.4
Olive oil, 1 tbsp.31.9
Peanuts, roasted, 1 oz.32.2
Spinach, raw, ½cup31.8
Spinach, cooked, ½cup2.51.6
Kiwi, 1 med.1.51.1
Mango, sliced, ½cup1.50.9

(Illustration by GGS Information Services/Thomson Gale.)

them. The damage that free radicals cause to cells is believed to play a role in the development of certain diseases, especially cancer. Many of the health claims for vitamin E are based on its antioxidant properties.

Description

Vitamin E is a collection of eight different, but closely related, compounds. These are alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol. Each of these compounds has a different degree of activity in humans. Alpha-tocopherol is the most active form. Vitamin E in dietary supplements is usually a synthetic compound called alpha-tocopherol acetate. Synthetic alpha-tocopherol is sometimes labeled dl-alpha-tocopherol.

Normal vitamin E requirements

The United States Institute of Medicine (IOM) of the National Academy of Sciences has developed values called Dietary Reference Intakes (DRIs) for vitamins and minerals. The DRIs consist of three sets of numbers. The Recommended Dietary Allowance (RDA) defines the average daily amount of the nutrient needed to meet the health needs of 97-98% of the population. The Adequate Intake (AI) is an estimate set when there is not enough information to determine an RDA. The Tolerable Upper Intake Level (UL) is the average maximum amount that can be taken daily without risking negative side effects. The DRIs are calculated for children, adult men, adult women, pregnant women, and breastfeeding women.

The IOM has not set RDA or UL values for vitamin E in children under one year old because of incomplete scientific information. Instead, it has set AI levels for this age group. Recently the UL level has become somewhat controversial and has been challenged by some researchers as being set too high. AI and UL levels are measured in both weight (milligrams or mg) and international units (IU). The IU measurement is the measurement used on dietary supplement labels. For the alpha-tocopherol form of vitamin E, 1 mg equals about 1.5 IU.

The following are the AIs, RDAs, and ULs for alpha-tocopherol for healthy individuals:

  • infants birth-6 months: AI 6 IU or 4 mg
  • infants 7-12 months: AI 7.5 IU or 5 mg
  • children 1-3 years: RDA 9 IU of 6 mg; UL 300 IU or 200 mg .
  • children 4-8 years: RDA 10.5 IU or 7 mg; UL 450 IU or 300 mg .
  • children 9-13 years: RDA 16.5 IU or 11 mg; UL 900 IU or 600 mg .
  • children 14-18 years: RDA 22.5 IU or 15 mg; UL 1,200 IU or 800 mg .
  • adults age 19 and older: RDA 22.5 IU or 15 mg; UL 1,500 IU or 1,000 mg .
  • pregnant women: RDA 22.5 IU or 15 mg; UL 1,500 IU or 1,000 mg .
  • breastfeeding women: RDA 28.5 IU or 19 mg; UL 1,500 IU or 1,000 mg

Sources of vitamin E

Vitamin E is found in limited amounts in a small number of foods. These include some oils, nuts, and green leafy vegetables. Vitamin E is also added to some breakfast cereals, which say“fortified with vitamin E” on the label. In addition, the Food and Drug Administration requires all foods containing olestra, a compound that reduces fat absorption, to be fortified with the fat-soluble vitamins A, D, E, and K.

The following list gives the approximate vitamin E (alpha-tocopherol) content for some common foods:

KEY TERMS

Antioxidant —A molecule that prevents oxidation. In the body antioxidants attach to other molecules called free radicals and prevent the free radicals from causing damage to cell walls, DNA, and other parts of the cell.

Dietary supplement —A product, such as a vitamin, mineral, herb, amino acid, or enzyme, that is intended to be consumed in addition to an individual's diet with the expectation that it will improve health.

Fat-soluble vitamin —A vitamin that dissolves in and can be stored in body fat or the liver.

Retina —The layer of light-sensitive cells on the back of the eyeball that function in converting light into nerve impulses.

Vitamin —A nutrient that the body needs in small amounts to remain healthy but that the body cannot manufacture for itself and must acquire through diet.

  • wheat germ oil, 1 Tablespoon: 30.5 UL or 20.3 mg
  • olive oil, 1 Tablespoon: 3 UL or 1.9 mg . sunflower oil, 1 Tablespoon: 8.5 UL or 5.6 mg
  • safflower oil, 1 Tablespoon: 6 UL or 4.6 mg . almonds, roasted, 1 ounce: 11 UL or 7.4 mg
  • peanuts, roasted, 1 ounce: 3 UL or 2.2 mg . peanut butter, fortified, 1 ounce: 6 UL or 4.2 mg
  • hazelnuts, roasted, 1 ounce: 6.5 UL or 4.3 mg . spinach, cooked ½ cup: 2.5 UL or 1.6 mg
  • spinach, raw ½ cup: 3 UL or 1.8 mg . mango, ½ cup sliced: 1.5 UL or 0.9 mg
  • kiwi, 1 medium: 1.5 UL or 1.1 mg . avocado, 1 medium: 5 UL or 3.4 mg
  • multivitamin: 30-60 IU or 20-40 mg . vitamin E dietary supplement: 400-800 IU or 270-530 mg

Vitamin E's role in health

Vitamin E's role in health not completely clear, but experts do agree on what happens when vitamin E is absent from the diet. Vitamin E deficiency results in damage to the nerves, especially the nerves of the hands and feet, loss of coordination, a poor sense of balance, and muscle weakness. The retina of the eye can also be damaged, resulting in loss of vision. Signs of vitamin E deficiency often take years to develop in adults; the results are seen much sooner in children.

Almost all healthy people living in the developed world get enough vitamin E through diet to prevent symptoms of vitamin E deficiency from developing. There is some debate, however, about the frequency with which deficiencies exist that do not produce obvious symptoms (subclinical deficiencies). Those at greatest risk for vitamin E deficiency include:

  • severely premature infants who weigh less that 3 lb 4 oz (1,500 g) at birth
  • people with gastrointestinal diseases such as Crohn's disease, cystic fibrosis, or inflammatory bowel disease that interfere with the absorption of fat from the intestine
  • people who have had part of their stomach or intestine surgically removed for weight loss or other reasons . people eating very low fat diets for an extended time
  • people with anorexia nervosa (self-starvation)
  • people with the rare inherited disorders abetalipo-proteinemia and ataxia and vitamin E deficiency (AVED), both of which prevent normal use of vitamin E

Controversy about vitamin E centers on its use as a dietary supplement to help prevent or treat disease. Many health claims are based on the antioxidant properties of vitamin E. Initially, it appeared that large doses of vitamin E could help prevent heart disease and some cancers. Then in 2004, researchers at the Johns Hopkins University School of Medicine re-analyzed the data (a meta-analysis) from 19 major clinical trials that included more than 136,000 individuals. They found that taking 400IU or more of vitamin E daily increased a person's risk of death by about 4%. However, some experts have questioned the validity of the Johns Hopkins analysis. The role of vitamin E is further complicated by the fact that it comes in many forms, and researchers are not completely clear on what, if any, roles the different forms play in maintaining human health. Clinical trials are currently underway to determine safety and effectiveness of vitamin E in a variety of situations. Individuals interested in participating in a clinical trial at no charge can find a list of open trials http://www.clinicaltrials.gov.

CARDIOVASCULAR DISEASE. Since the 1940s, researchers have suggested that vitamin E might protect against heart disease. This theory is based on its activity as an antioxidant. Because vitamin E oxidizes (neutralizes) LDL or“bad” cholesterol, researchers have suggested that large doses of vitamin E may slow or prevent the build-up of material on the wall of arteries and thus help prevent cardiovascular disease.

Results of studies testing this idea are mixed. Several large studies followed healthy people who took vitamin E and looked for a correlation between the amount of vitamin E in their diet and whether they were diagnosed with heart disease or died of a heart attack. Two studies found that people who got least 7 mg of alpha-tocopherol daily from food were about one-third less likely to die from heart disease than those people who consumed 5 mg of less of alpha-tocopherol. On the other hand, another large, well-designed study (the Heart Outcomes Prevention Evaluation) found no cardiovascular benefit to large doses of vitamin E. A well-controlled study (the CHAOS study) done in Great Britain found that when people who already had heart disease were given large doses (400 IU or 800 IU) of Vitamin E, the rate of non-fatal heart attacks dropped dramatically, but that the overall death rate from heart disease did not change.

The official position of the American Heart Association published in its“Diet and Lifestyle Recommendations Revision 2006” is that“Antioxidant supplements have not been shown to be helpful in preventing heart disease and are not recommended in these guidelines.” The recommendations specifically mention the possibility of“an increased risk of heart failure and the possibility of increased total mortality (death) from high dose vitamin E supplements.” More research needs to be done in this area.

CANCER. The antioxidant activities of vitamin E are also thought to help protect against the development of cancer by removing free radicals that damage cell membranes and DNA. Vitamin E is also believed to neutralize nitrosamines. Nitrosamines are known carcinogens found in tobacco and smoked meats. Much of the evidence for the action of vitamin E on cancer comes from animal studies. The results of human studies are inconclusive and often confusing. According to the American Cancer Society, there is some evidence that vitamin E may have a protective effect against coon, rectal, bladder, and prostate cancer, but not other cancers. There is no evidence that vitamin E slows the growth of cancer once it has already developed, and some conflicting evidence about whether it interferes with the effectiveness of chemotherapy and radiation therapy. Research on the relationship of vitamin E and cancer continues.

CATARACTS. Cataracts form on the lens of the eye, making it cloudy and reducing vision. They are thought to form because proteins in the lens are oxidized. Ten studies have been done to see if the antioxidant properties of vitamin E are effective in preventing cataracts. Five studies found a protective effect, while five others found no effect.

Precautions

There is a great deal of debate about how much vitamin E is too much. The UL for healthy adults in the United States is 1,500 IU daily. However, some experts feel this is too high, especially since it is based on research done in the 1950s. They argue that UL should be lower since the Johns Hopkins study found that daily amounts over 400 IU increased the death rate and protective effects of larger doses of vitamin E are still unproven. In the United Kingdom, the recommended daily limit of vitamin E is 800 UI.

Large doses of vitamin E increase the chance of bleeding. People who are taking blood-thinning medications such as warfarin (Coumadin), heparin, and clopidogrel (Plavix) should discuss the use of vitamin E with their healthcare providers. Other people who should be wary of taking vitamin E as a dietary supplement are those who are vitamin K deficient, who have liver damage, and those with a history of bleeding ulcers. Vitamin E supplementation should be stopped about one month before surgery because of the increased risk of bleeding. Other possible, but uncommon, side effects of vitamin E supplementation include nausea, vomiting, diarrhea, damage to the retina, breast soreness, fatigue, emotional disturbances, and thyroid hormone disturbances.

Interactions

Vitamin E may interact with the following:

  • When taken with blood-thinning drugs, vitamin E may increase the likelihood of bleeding.
  • When taken with nonsteroidal anti-inflammatory (NSAIDs) drugs such as ibuprofen (Motrin, Advil) or naproxen (Aleve, Naprosyn), vitamin E may increase the likelihood of bleeding.
  • Cholestyramine (Questran) and colestipol (Colestid) may decrease vitamin E absorption.
  • Orlistat (Xenical, Alli) decreases Vitamin E absorption.
  • Olestra, a fat substitute in foods, decreases the absorption of vitamin E.

Complications

No complications are expected when vitamin E is used in the recommended amounts. The complications resulting from insufficient or excess use are discussed above.

Resources

BOOKS

Gaby, Alan R., ed. A-Z Guide to Drug-Herb-Vitamin Interactions Revised and Expanded 2nd Edition: Improve Your Health and Avoid Side Effects When Using Common Medications and Natural Supplements Together. New York: Three Rivers Press, 2006.

Lieberman, Shari and Nancy Bruning. The Real Vitamin and Mineral Book: The Definitive Guide to Designing Your Personal Supplement Program, 4th ed. New York: Avery, 2007.

Preedy, Victor R. and Ronald R. Watson, eds. The Encyclopedia of Vitamin E. Wallingford, Oxfordshire, UK : CABI International, 2007.

Pressman, Alan H. and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals, 3rd ed. Indianapolis, IN: Alpha Books, 2007.

Rucker, Robert B., ed. Handbook of Vitamins. Boca Raton, FL: Taylor & Francis, 2007.

PERIODICALS

Schardt, David.“Is Vitamin E Dangerous?” Nutrition Action Healthletter 32, no.4 (May 1, 2005):12.

ORGANIZATIONS

American Cancer Society. 1599 Clifton Road NE, Atlanta GA 30329-4251. Telephone: (800) ACS-2345. Website: <http://www.cancer.org.>

American Heart Association. 7272 Greenville Avenue, Dallas, TX 75231. Telephone: (800) 242-8721. Website: <http://www.americanheart.org.>

American Dietetic Association. 120 South Riverside Plaza, Suite 2000, Chicago, Illinois 60606-6995. Telephone: (800) 877-1600. Website: http://www.eatright.org/

Linus Pauling Institute. Oregon State University, 571 Weniger Hall, Corvallis, OR 97331-6512. Telephone: (541) 717-5075. Fax: (541) 737-5077. Website: <http://lpi.oregonstate.edu/>

Office of Dietary Supplements, National Institutes of Health. 6100 Executive Blvd., Room 3B01, MSC 7517, Bethesda, MD 20892-7517 Telephone: (301)435-2920. Fax: (301)480-1845. Website: <http://dietary-supplements.info.nih.gov/>

OTHER

American Cancer Society“Vitamin E.” American Cancer Society, June 1, 2005. <http://www.cancer.org/docroot/ETO/content/ETO_5_3X_Vitamin_E.asp?sitearea=ETO.>

American Heart Association Nutrition Committee.“Diet and Lifestyle Recommendations Revision 2006.” American Heart Association, June 19, 2006. <http://www.americanheart.org/presenter.jhtml?identifier=3040741>

Higdon, Jane.“Vitamin E.”Linus Pauling Institute-Oregon State University, November 11, 2004. <http://lpi.oregonstate.edu/infocenter/vitamins/VitaminE

Harvard School of Public Health.“Vitamins.” Harvard University, November 10, 2006. <http://www.hsph.harvard.edu/nutritionsource/vitamins.html>

Johns Hopkins University School of Medicine. “Study Shows High-dose Vitamin E Supplements May Increase Risk of Dying.” Johns Hopkins University, November 10. 2004. <http://www.hopkinsmedicine.org/Press_releases/2004/11_10_04.html>

Maryland Medical Center Programs Center for Integrative Medicine. “Vitamin E.” University of Maryland Medical Center, April 2002. <http://www.umm.edu/altmed/ConsSupplements/VitaminEcs.html.>

Medline Plus.“Vitamin E.” U. S. National Library of Medicine, August 1, 2006. <http://www.nlm.nih/gov/medlineplus/druginfo/natural/patient-vitamine.html>

Office of Dietary Supplements.”Vitamin E.“National Institutes of Health, January 23, 2007. <http://dietary-supplements.info.nih.gov/factsheets/vitamine.asp>

Tish Davidson, A.M.

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Vitamin E

Vitamin E

Definition

Vitamin E is a antioxidant vitamin found in many foods or can be taken as a supplement.

Description

Vitamin E naturally exists in eight different forms; four tocopherols: alpha tocopherol, beta tocopherol, gamma tocopherol, delta tocopherol and four tocotrienols: alpha tocotrienol, beta tocotrienol, gamma tocotrienol and delta tocotrienol. Each form has a slightly different activity in the body. The most active form in humans is alpha tocopherol and vitamin E supplements are often sold as alpha tocopherol acetate.

Synthetic vitamin E is labeled as “D, L” or “d, l” tocopherol. Since only the “D” or “d” form of the vitamin is active, the D, L or d, l form is only half as active as the naturally occurring form, which is D or d. When vitamin E is supplied as a mixture of different forms it is often referred to as mixed tocopherols, which is considered by many to be the most useful form.

The most important role of vitamin E is as an antioxidant protecting cells against free radical damage. Damage by free radicals can lead to several diseases including heart disease and cancer . Although vitamin E deficiency in humans is rare, it can occur in several situations:

  • People with disorders that affect absorption of fat from the intestines including cystic fibrosis, Crohn's disease or the inherited conditions abetalipoproteinemia, and ataxia and vitamin E deficiency (AVED) may be at risk.
  • Premature or low birth weight infants and people on a very low fat diet.
  • Deficiencies in vitamin E are associated with unsteady walking or poor coordination, muscle weakness, nerve degeneration in hands and feet.

Prolonged and severe vitamin E deficiencies can lead to blindness, abnormal heart rhythms and dementia.

A number of investigations are underway to evaluate the ability of vitamin E to prevent chronic disease. Vitamin E has been promoted for the following uses:

  • as an immune stimulant
  • prevention of macular degeneration, cataracts, Parkinson's disease, premenstrual syndrome, and cancer
  • treatment for anemia and angina
  • prevention or treatment of atherosclerosis
  • reducing the side effects of cisplatin for chemotherapy
  • as a cancer treatment itself
  • prevention of heart disease in dialysis patients
  • prevention or slowing of dementia
  • prevention or improvement of diabetes
  • prevention of scars
  • lowering high cholesterol levels

Much of the research remains inconclusive or very preliminary. More significant research has been done in the areas of heart disease, cancer, and dementia or Alzheimer's disease.

Because oxidative injury is thought to play a role in the development of both cancer and heart disease it seems logical that taking antioxidants such as vitamin E should reduce the risk of both. Laboratory studies show several small benefits to alpha tocopherol related to cancer and heart disease, such as decreased platelet aggregation and inhibiting cell growth. Several epidemiology studies have also shown a lower risk of heart disease and cancer associated with people who have an increased ingestion of vitamin E either from diet or supplements. However, when randomized, controlled, clinical trials have been done to follow up and confirm a role for vitamin E supplementation in reducing cancer risks or cardiovascular disease risks the results have not usually been positive.

A study published in the Journal of the American Medical Association (JAMA) in 2005 compared individuals taking 400 IU/d of vitamin E (alpha tocopherol) to volunteers taking no vitamin E. After seven years there was no significant difference between groups in the occurrence of cancer or cardiovascular disease. In fact, researchers noticed a slight increase in heart failure in the vitamin E group. A second study from the same year evaluated all published results from studies involving vitamin E. The study concluded that regular high doses of vitamin E (400 IU/day or more) slightly increased the risk of death for any reason compared with individuals who did not take vitamin E. It is, therefore, recommended that doses higher than 400 IU/day be avoided.

In 2008, a review of studies that evaluated the use of vitamin E for Alzheimer's disease was published.

The review found that, although fewer patients taking vitamin E progressed to incapacity compared to control groups who took no vitamin E, more patients taking vitamin E experienced falls . The review concluded that as of yet there is no evidence that vitamin E is beneficial for those with Alzeheimer's disease or mild cognitive impairment.

QUESTIONS TO ASK YOUR PHARMACIST

  • Is vitamin E useful in treating my condition?
  • What is the recommended dose for vitamin E supplements?
  • How do I know if I have vitamin E deficiency?
  • Will vitamin E supplements interact with my other medications?

Although some studies show that deficiencies of vitamin E are linked to increased risk of heart disease, taking vitamin E supplements does not decrease the risk of heart disease or cancer. The best way to get vitamin E is through food. Foods high in vitamin E include vegetable oils, wheat germ oil in particular; nuts including peanuts; green leafy vegetables; eggs; and whole grains and fortified cereals. Food supplies all eight forms of vitamin E and other antioxidants. Eating a variety of foods is important in order to get enough vitamin E and other antioxidants. Cooking and storage of foods can be detrimental to vitamin E content.

Recommended dosage

The recommended daily allowance (RDA) for vitamin E in adults is 15 mg or 22.5 International Units (IU). RDAs for vitamin E are only based on alpha tocopherol. Amounts of vitamin E in foods are typically given as IUs. The upper tolerable limit recommended for vitamin E is 1,000 mg (1,500 IUs) daily. Vitamin E deficiency in North Americans is rare with most people getting adequate levels from foods.

Precautions

Because the FDA does not regulate herbs and supplements, there is no guarantee of strength, purity or safety of these products. Contact dermatitis has been reported with topical use. Recent reports indicate that regular doses of 400 IU or greater per day can slightly increase the risk of death. It is wise to study current research on vitamin E and ask a physician about the latest recommendations. Very few long term studies have been done to document risks or benefits of vitamin E supplementation.

Use of vitamin E should be avoided if the patient has a rare eye condition called retinitis pigmentosa. Taking vitamin E with this condition has been associated with an increased loss of vision. The absorption of vitamin E is dependent on the presence of other fats so vitamin E supplements are best taken with a meal.

KEY TERMS

Antioxidants —Particles that seek out and destroy free radicals, by-products of oxygen use, to prevent damage to the body.

Contact dermatitis —Rash or irritation of the skin caused by contact with a substance.

Epidemiology —A branch of science that studies the frequency and distribution of disease in a population.

Free radicals —The by-products of oxidation, these molecules can cause damage throughout the body.

Recommended Daily Allowance (RDA) —The amount of a specific nutrient that should be consumed each day for optimal health. This standard is set and periodically updated by U.S. government agencies.

Vitamin E deficiency —Failure to obtain the necessary levels of vitamin E through food.

Side effects

Vitamin E supplementation at doses higher than 400 IU/day have been associated with increased risk of bleeding, particularly in patients taking anticoagulants such as warfarin, heparin or aspirin . Regular high doses of vitamin E are also linked to increased risk of death from all causes. Caution should be taken when ingesting large amounts of vitamin E.

Side effects for short term use of vitamin E include contact dermatitis on the skin, abdominal pain, diarrhea , nausea, gonadal dysfunction, diminished kidney function, dizziness , fatigue, headache, weakness or blurred vision. These side effects are rare.

Interactions

Zinc deficiency may also be related to decreases in vitamin E. Vitamin E can interfere with antidepressant drugs, antipsychotic drugs , aspirin, beta blockers for high blood pressure , chloroquine for malaria, and cyclosporine for cancer. Patients should notify their physician if they take any of these drugs with vitamin E.

Caregiver concerns

Caregivers should monitor the use of vitamin E supplements in older adults. Any adverse side effects from taking supplements should be reported to the patient's physician. Caregivers should also learn to recognize symptoms of vitamin E deficiency and discuss these concerns with the physician.

Resources

PERIODICALS

Lonn, E., et al. “Effects of Long-term Vitamin E Supplementation on Cardiovascular Events and Cancer: A Randomized Controlled Trial.” Journal of the American Medical Association (JAMA) 293, no. 11 (March 16, 2005): 1338–1347.

Miller, E. R., et al. “Meta-Analysis: High-Dosage Vitamin E Supplementation May Increase All-Cause Mortality.” Annals of Internal Medicine 142, no. 1 (January 4, 2005).

OTHER

“Possible Interactions With: Vitamin E.” Adam.com. 2002 [cited April 15, 2008]. http://www.ajc.com/health/altmed/shared/health/alt_medicine/ConsSupplements/Interactions/VitaminEcs.html.

“Vitamin E.” Drugs & Supplements. November 1, 2005 [cited April 14, 2005]. The Natural Standard Research Collaboration. http://www.mayoclinic.com/health/vitamine/NS_patient-vitamin-e.

“Vitamin E.” Office of Dietary Supplements, National Institutes of Health. January 23, 2007 [cited April 15, 2008]. http://dietary-supplements.info.nih.gov/factsheets/vitamine.asp.

Cindy L. A. Jones Ph.D.

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Vitamin E

Vitamin E

Description

Vitamin E is an antioxidant responsible for proper functioning of the immune system and for maintaining healthy eyes and skin. It is actually a group of fat soluble compounds known as tocopherols (i.e., alpha tocopherol and gamma tocopherol). Gamma tocopherol accounts for approximately 75% of dietary vitamin E. Vitamin E rich foods include nuts, cereals, beans, eggs, cold-pressed oils, and assorted fruits and vegetables. Because vitamin E is a fat soluble vitamin, it requires the presence of fat for proper absorption. Daily dietary intake of the recommended daily allowance (RDA) of vitamin E is recommended for optimum health.

Vitamin E is absorbed by the gastrointestinal system and stored in tissues and organs throughout the body. Certain health conditions may cause vitamin E depletion, including liver disease, celiac disease, and cystic fibrosis . Patients with end-stage renal disease (kidney failure) who are undergoing chronic dialysis treatment may be at risk for vitamin E deficiency. These patients frequently receive intravenous infusions of iron supplements which can act against vitamin E.

Vitamin E deficiency can cause fatigue, concentration problems, weakened immune system, anemia, and low thyroid levels. It may also cause vision problems and irritability. Low serum (or blood ) levels of vitamin E have also been linked to major depression.

General use

Vitamin E is necessary for optimal immune system functioning, healthy eyes, and cell protection throughout the body. It has also been linked to the prevention of a number of diseases. The therapeutic benefits of vitamin E include:

  • Cancer prevention. Vitamin E is a known antioxidant, and has been associated with a reduced risk of gastrointestinal, cervical, prostate, lung, and possibly breast cancer .
  • Immune system protection. Various studies have shown that vitamin E supplementation, particularly in elderly patients, boosts immune system function. Older patients have demonstrated improved immune response , increased resistance to infections, and higher antibody production. Vitamin E has also been used with some success to slow disease progression in HIV-positive patients.
  • Eye disease prevention. Clinical studies on vitamin E have shown that supplementation significantly reduces the risk for cataracts and for macular degeneration , particularly among women.
  • Memory loss prevention. Vitamin E deficiency has been linked to poor performance on memory tests in some elderly individuals.
  • Alzheimer's disease treatment. In a study performed at Columbia University, researchers found that Alzheimer's patients who took daily supplements of vitamin E maintained normal functioning longer than patients who took a placebo.
  • Liver disease treatment. Vitamin E may protect the liver against disease.
  • Diabetes treatment. Vitamin E may help diabetic patients process insulin more effectively.
  • Pain relief. Vitamin E acts as both an anti-inflammatory and analgesic (or pain reliever). Studies have indicated it may be useful for treatment of arthritis pain in some individuals.
  • Parkinson's disease prevention. High doses of vitamin E intake was associated with a lowered risk of developing Parkinson's disease in one 1997 Dutch study.
  • Tardive dyskinesia treatment. Individuals who take neuroleptic drugs for schizophrenia or other disorders may suffer from a side effect known as tardive dyskinesia, in which they experience involuntary muscle contractions or twitches. Vitamin E supplementation may lessen or eliminate this side effect in some individuals.

Other benefits of vitamin E are less clear cut, and have been called into question with conflicting study results or because of a lack of controlled studies to support them. These include:

  • Heart disease prevention. A number of epidemiological studies have indicated that vitamin E may prevent heart disease by lowering total blood cholesterol levels and preventing oxidation of LDL cholesterol. However, a large, controlled study known as the Heart Outcomes Prevention Evaluation (HOPE) published in early 2000 indicates that vitamin E does not have any preventative effects against heart disease. The study followed 9,500 individuals who were considered to be at a high risk for heart disease. Half the individuals were randomly chosen to receive vitamin E supplementation, and the other half of the study population received a placebo. After five years, there was no measurable difference in heart attacks and heart disease between the two patient populations. Still, vitamin E may still hold some hope for heart disease prevention. It is possible that a longer-term study beyond the five years of the HOPE study may demonstrate some heart protective benefits of vitamin E consumption. It is also possible that while the high-risk patient population that was used for the HOPE study did not benefit from vitamin E, an average-risk patient population might still benefit from supplementation. It is also possible that vitamin E needs the presence of another vitamin or nutrient substance to protect against heart disease. Further large, controlled, and long-term clinical studies are necessary to answer these questions.
  • Skin care. Vitamin E is thought to increase an individual's tolerance to UV rays when taken as a supplement in conjunction with vitamin C . Vitamin E has also been touted as a treatment to promote faster healing of flesh wounds . While its anti-inflammatory and analgesic properties may have some benefits in reducing swelling and relieving discomfort in a wound, some dermatologists dispute the claims of faster healing, and there are no large controlled studies to support this claim.
  • Hot flashes. In a small study conducted at the Mayo Clinic, researchers found that breast cancer survivors who suffered from hot flashes experienced a decrease in those hot flashes after taking vitamin E supplementation.
  • Muscle maintenance and repair. Recent research has demonstrated that the antioxidative properties of vitamin E may prevent damage to tissues caused by heavy endurance exercises. In addition, vitamin E supplementation given prior to surgical procedures on muscle and joint tissues has been shown to limit reperfusion injury (muscle damage which occurs when blood flow is stopped, and then started again to tissues or organs).
  • Fertility. Vitamin E has been shown to improve sperm function in animal studies, and may have a similar effect in human males. Further studies are needed to establish the efficacy of vitamin E as a treatment for male infertility.

Preparations

The U.S. recommended dietary allowance (RDA) of the alpha-tocopherol formulation of vitamin E is as follows:

  • men: 10 mg or 15 IU
  • women: 8 mg or 12 IU
  • pregnant women: 10 mg or 15 IU
  • lactating women: 12 mg or 18 IU

In April 2000, the National Academy of Sciences recommended changing the RDA for vitamin E to 22 international units (IUs), with an upper limit (UL), or maximum daily dose, of 1500 IUs. Daily values for the vitamin as recommended by the U.S. Food and Drug Administration, the values listed on food and beverage

labeling, remain at 30 IUs for both men and women age four and older.

Many nuts, vegetable-based oils, fruits, and vegetables contain vitamin E. Foods rich in vitamin E include wheat germ oil (26.2 mg/tbsp), wheat germ cereal (19.5 mg/cup), peanuts (6.32 mg/half cup), soy beans (3.19 mg/cup), corn oil (2.87/tbsp), avocado (2.69 mg), and olive oil (1.68 mg/tbsp.). Grapes, peaches, broccoli, Brussels sprouts, eggs, tomatoes, and blackberries are also good sources of vitamin E. Fresh, raw foods contain the highest levels of the vitamin. Both heat and light can reduce vitamin and mineral potency in fresh foods, so overcooking and improper storage should be avoided. Sliced and chopped foods have more of their surface exposed to light, therefore keeping vegetables and fruits whole may also help to maintain full vitamin potency.

For individuals considered at risk for vitamin E deficiency, or those with an inadequate dietary intake, vitamin E supplements are available in a variety of different forms, including pills, capsules, powders, and liquids for oral ingestion. For topical use, vitamin E is available in ointments, creams, lotions, and oils. Vitamin E is also available commercially as one ingredient of a multivitamin formula.

The recommended daily dosage of vitamin E varies by individual need and by the amount of polyunsaturated fats an individual consumes. The more polyunsaturated fats in the diet, the higher the recommended dose of vitamin E, because vitamin E helps to prevent the oxidizing


KEY TERMS


Antioxidants —Enzymes which bind with free radicals to neutralize their harmful effects.

Contact dermatitis —Inflammation, redness, and irritation of the skin caused by an irritating substance.

Epidemiological study —A study which analyzes health events and trends in particular patient populations.

Free radicals —Reactive molecules created during cell metabolism that can cause tissue and cell damage like that which occurs in aging and with disease processes such as cancer.

Macular degeneration —Degeneration, or breakdown, of the retina that can lead to partial or total blindness.

Non-heme iron —Dietary or supplemental iron that is less efficiently absorbed by the body than heme iron (ferrous iron).

Reperfusion —The reintroduction of blood flow to organs or tissues after blood flow has been stopped for surgical procedures.

Vitamin A —An essential vitamin found in liver, orange and yellow vegetables, milk, and eggs that is critical for proper growth and development.

Vitamin K —A fat-soluble vitamin responsible for blood clotting, bone metabolism, and proper kidney function.


effects of these fats. Because vitamin E is fat soluble, supplements should always be taken with food.

Supplements are also available in either natural or synthetic formulations. Natural forms are extracted from wheat germ oil and other vitamin E food sources, and synthetic forms are extracted from petroleum oils. Natural formulas can be identified by a d prefix on the name of the vitamin (i.e., d-alpha-tocopherol).

Precautions

Overdoses of vitamin E (over 536 mg) can cause nausea, diarrhea , headache, abdominal pain, bleeding, high blood pressure , fatigue, and weakened immune system function.

Patients with rheumatic heart disease, iron deficiency anemia , hypertension , or thyroid dysfunction should consult their healthcare provider before starting vitamin E supplementation, as vitamin E may have a negative impact on these conditions.

Side effects

Vitamin E is well-tolerated, and side effects are rare. However, in some individuals who are vitamin K deficient, vitamin E may increase the risk for hemorrhage or bleeding. In some cases, side effects may be decreased or eliminated by adjusting the dosage of vitamin E and vitamin K.

Vitamin E ointments, oils, or creams may trigger an allergic reaction known as contact dermatitis. Individuals who are considering using topical vitamin E preparations for the first time, or who are switching the type of vitamin E product they use, should perform a skin patch test to check for skin sensitivity to the substance. A small, dime sized drop of the product should be applied to a small patch of skin inside the elbow or wrist. The skin patch should be monitored for 24 hours to ensure no excessive redness, irritation, or rash occurs. If a reaction does occur, it may be in response to other ingredients in the topical preparation, and the test can be repeated with a different vitamin E formulation. Individuals who experience a severe reaction to a skin patch test of vitamin E are advised not to use the product topically. A dermatologist or other healthcare professional may be able to recommend a suitable alternative.

Interactions

Individuals who take anticoagulant (blood thinning) or anticonvulsant medications should consult their healthcare provider before starting vitamin E supplementation. Vitamin E can alter the efficacy of these drugs.

Non-heme, inorganic iron supplements destroy vitamin E, so individuals taking iron supplements should space out their doses (e.g., iron in the morning and vitamin E in the evening).

Large doses of vitamin A can decrease the absorption of vitamin E, so dosage adjustments may be necessary in individuals supplementing with both vitamins .

Alcohol and mineral oil can also reduce vitamin E absorption, and these substances should be avoided if possible in vitamin E deficient individuals.

Resources

BOOKS

Reavley, Nocola. The New Encyclopedia of Vitamins, Minerals, Supplements, and Herbs. New York: M. Evans & Company, 1998.

PERIODICALS

"Vitamin E: E for Exaggerated?" Harvard Health Letter 25, no. 5 (March 2000): 6.

ORGANIZATIONS

United States Department of Agriculture. Center for Nutrition Policy and Promotion. 1120 20th Street NW, Suite 200, North Lobby, Washington, D.C. 20036. (202) 418-2312. <http://www.usda.gov/cnpp/>.

Paula Ford-Martin

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Vitamin E

Vitamin E

Vitamin E is the name given to a group of eight chemicals with similar properties that are essential to health. Vitamin E was first isolated as a distinct substance in various green leafy vegetables in 1922. Vitamin E is classed as a micronutrient, a substance that is not required in large quantities through diet but which is otherwise essential to the maintenance of good health. In all of its forms, vitamin E is an organic (carbon-based) compound, of which alpha tocopherol is the most prolific. Vitamin E is often referred to as nature's antioxidant, a testament to the important function of these chemicals within the body.

Vitamin E, as with all micronutrients, is required in trace amounts for bodily function. The recommended daily requirement for adults of this substance is 15 mg per day. The consumption of dietary supplements to ensure the ingestion of the required quantities of vitamin E is unnecessary if the person is consuming a well-balanced diet, as the best sources of the chemical are commonly available food products, such as wheat and its large number of byproducts, many green leafy vegetables, and most nuts, seeds, and their oils. Vitamin E is the least toxic of all fat-soluble vitamins; the recommended upper daily limit of vitamin E consumption is 1,000 mg.

Vitamin E is a fat-soluble compound. It is processed for entry into the body at the small intestine, where the vitamin is parceled into chemical packages made from both high density lipoproteins (HDLs) and low density lipoproteins (LDLs) to facilitate the absorption of vitamin E into both the lymphatic system and the liver. From these locations, vitamin E then is released directly into the bloodstream.

With either its HDL or LDL transportation in the bloodstream, vitamin E is carried to various cells within the body. As a fat-soluble vitamin, vitamin E can be stored within the cell mitochondria (often described as the cellular powerhouse) of the adipose tissue, the cells designed for the storage of triglycerides (fats), for an indefinite period. Once utilized as an antioxidant, the spent vitamin E is disposed of by the body through the stomach bile; it is ultimately excreted from the body as feces.

Oxidation is a biological concept that is readily understood with reference to many daily life examples. Rusted metal, food that turns rancid, and the various aging processes observable within the body are examples of oxidation, which is the decay or the degradation of a cell due to the effect of oxygen. An antioxidant, such as vitamin E, is any substance that by its presence or its operation, serves to specifically delay, prevent, or reverse the rate of deterioration caused in the cells by oxygen. Antioxidants are classed as one of two types: metal sequestrants, which prevent metals from reacting with oxygen, and free radical scavengers, which operate to interrupt the destructive chain reactions that occur within the body that are precipitated by the compounds known as free radicals. Vitamin E and, in certain circumstances, vitamin C, are free radical scavengers within the body.

Free radicals are the most common cause of oxidation within the body. Occurring throughout the body, these chemical compounds are inherently unstable, as their electron structure is unbalanced due to one or more electrons within the structure not being paired, which creates either a positive or negative electric charge within the free radical. The free radical therefore seeks to obtain the necessary electrons to create electrical balance from nearby stable compounds. This "theft" of electrons by the free radicals renders the previously stable compound unstable and reactive. This use precipitates a chain reaction of electron use that is the essence of the oxidation that causes cell damage.

As an antioxidant, vitamin E traps the free radicals that it encounters, through its donation of a hydrogen atom to the free radical molecule, rendering it chemically neutral. Vitamin E ranges throughout the tissues of the body, and it provides its antioxidant benefits to all aspects of the cardiovascular and musculoskeletal systems. Vitamin E does not differentiate between the types of free radicals it may encounter, nor does vitamin E restrict its actions based on the place of origin of the target free radical.

There is no question from a scientific perspective that vitamin E is a very important compound within the body, as it protects the tissues from decay and degradation. The companion issue of whether megadoses of vitamin E, by daily supplement or otherwise, will provide enhanced health protection has not been conclusively determined. The actions of vitamin E must also be considered separately from the healing and repair of tissue that occurs within the body. Antioxidant function is separate from the cell repair that occurs within the body at all cell production points—bone, connective tissue, muscles, and blood cells may be degraded by the actions of free radicals. Vitamin E does not play a role in cell production.

see also Diet; Free fatty acids in the blood; Nutrition; Oxygen.

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