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

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.

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 ]

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.

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).

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.

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

vitamin E See TOCOPHEROL.