Vitamin B complex

Description

The vitamin B complex consists of 12 related water-soluble substances. Eight are considered essential vitamins because they need to be included in the diet. Four are not essential because the body can synthesize them. Although these vitamins are chemically distinct, they are grouped together because they are found with one another in the same foods. Since they are water-soluble, most are not stored for any length of time, and must be replenished daily. The eight vitamins have both names and corresponding numbers. They are:

• B₁ (thiamin)
• B₂ (riboflavin )
• B₃ (niacin )
• B₅ (pantothenic acid )
• B₆ (pyridoxine )
• B₇ (biotin )
• B₉ (folic acid )
• B₁₂ (cobalamin)

Biotin is not always included among B complex supplements. The numbers that appear to have been skipped were found to be duplicate substances or non-vitamins. The four unnumbered components of the B complex that can be synthesized by the body are choline, inositol, PABA, and lipoic acid.

As a group, the B vitamins have a broad range of functions, including the maintenance of myelin, which is the covering of nerve cells. A breakdown of myelin can cause a large and devastating variety of neurologic symptoms. B vitamins are also key to producing energy from nutrients that are consumed. Three members of this group—folic acid, pyridoxine, and cobalamin—work together to keep homocysteine levels low. This is quite important, since high homocysteine levels are associated with heart disease . Some B vitamins prevent certain birth defects (including cleft palate and neural tube defects), maintain healthy red blood cells, support immune function, regulate cell growth, aid in hormone production, and may have a role in preventing certain types of cancer . They also help maintain healthy skin, hair, and nails.

General use

There are many claims regarding the usefulness of various B vitamins. Thiamine is thought to be supportive for people with Alzheimer's disease , a disorder that is also associated with low levels of pyridoxine and cobalamin. High doses of niacin lower cholesterol , and balance high-density (HDL) and low-density (LDL) lipoproteins. This should be done under medical supervision only. Some evidence shows that niacin may prevent juvenile diabetes (type 1, insulin dependent) in at-risk children. It may maintain pancreatic excretion of some insulin for a longer time than would occur normally. Niacin has also been used to relieve intermittent claudication and osteoarthritis , although the dose for the latter may lead to liver problems. The frequency of migraines may be significantly reduced, and the severity decreased, by the use of supplemental riboflavin. Pyridoxine is used therapeutically to lower the risk of heart disease, to relieve nausea associated with morning sickness , and to treat premenstrual syndrome (PMS). In conjunction with magnesium , pyridoxine may have some beneficial effects on the behavior of children with autism . Cobalamin supplementation has been shown to improve male fertility. Depression, dementia , and mental impairment are often associated with deficiencies of both cobalamin and folic acid. Folic acid may reduce the odds of cervical or colon cancer in certain risk groups.

Deficiency

Vitamin B complex is most often used to treat deficiencies that are caused by poor vitamin intake, difficulties with vitamin absorption, or conditions causing increased metabolism, such as hyperthyroidism , which deplete vitamin levels at a higher than normal rate.

Biotin and pantothenic acid are rarely deficient since they are broadly available in foods, but often persons lacking one type of B vitamin are lacking other B components as well. An individual who may have symptoms due to an inadequate level of one vitamin may suffer from an undetected underlying deficiency as well. One possibility of particular concern is that taking folic acid supplements can cover up the symptoms of cobalamin deficiency. This scenario could result in permanent neurologic damage if the cobalamin shortage remains untreated.

Some of the B vitamins have unique functions within the body that allow a particular deficiency to be readily identified. Often, however, they work in concert so symptoms due to various inadequate components may overlap. In general, poor B vitamin levels will cause profound fatigue and an assortment of neurologic manifestations, which may include weakness, poor balance, confusion, irritability, memory loss , nervousness, tingling of the limbs, and loss of coordination. Depression may be an early sign of significantly low levels of pyridoxine, as well as other B vitamins. Additional symptoms of vitamin B deficiency are sleep disturbances, nausea, poor appetite, frequent infections , and skin lesions.

A certain type of anemia (megaloblastic) is an effect of inadequate cobalamin. This anemia can also occur if a person stops secreting enough intrinsic factor in the stomach. Intrinsic factor is essential for the absorption of cobalamin. A lack of intrinsic factor also leads to pernicious anemia, so called because it persists despite iron supplementation. Neurologic symptoms often precede anemia when cobalamin is deficient.

A severe and prolonged lack of niacin causes a condition called pellagra. The classic signs of pellagra are dermatitis , dementia, and diarrhea . It is very rare now, except in alcoholics, strict vegans, and people in areas of the world with very poor nutrition .

Thiamine deficiency is similarly rare, except among the severely malnourished and alcoholics. A significant depletion causes a condition known as beriberi, which can cause weakness, leg spasms, poor appetite, and loss of coordination. Wernicke-Korsakoff syndrome is the most severe form of deficiency, and occurs in conjunction with alcoholism . Early stages of neurologic symptoms are reversible, but psychosis and death may occur if the course is not reversed.

Risk factors for deficiency

People are at higher risk for deficiency if they have poor nutritional sources of B vitamins, take medications, or have conditions that impair absorption, or are affected by circumstances causing them to require above-normal levels of vitamin B components. Since the B vitamins often work in harmony, a deficiency in one type may have broad implications. Poor intake of B vitamins is most often a problem in strict vegetarians and the elderly. People who frequently fast or diet may also benefit from B vitamin supplements. Vegans need to use brewer's yeast or other sources of supplemental cobalamin, since the only natural sources are meats.

Risk factors that may decrease absorption of some B vitamins include smoking ; excessive use of alcohol; surgical removal of portions of the digestive tract; and advanced age. Absorption is also impaired by some medications. Some of the drugs that may cause decreased absorption are corticosteroids, colchicine, metformin, phenformin, omeprazol, colestipol, cholestyramine, methotrexate, 5-fluorouracil, tricyclic antidepressants, and slow-release potassium .

A person's requirement for vitamin B complex may be increased by such conditions as pregnancy , breast-feeding, emotional stress , and physical stress due to surgery or injury. People who are very physically active require extra riboflavin. Use of birth control pills also increases the need for certain B vitamins.

Recent research indicates that children with sickle cell anemia are at high risk for elevated homocysteine levels and pyridoxine deficiency.

Studies of folic acid deficiency caused by cancer chemotherapy indicate that some patients are at greater risk than others due to genetic variations in metabolism of the B vitamins. Further research is needed to determine the role of these genetic factors in vitamin deficiency states.

Preparations

Natural sources

Although they are prevalent in many foods, fresh meats and dairy products are the best sources for most of the B vitamins. Cobalamin is only found naturally in animal source foods. Freezing of food and exposing foods or supplements to light may destroy some of the vitamin content. Dark-green leafy vegetables are an excellent source of folic acid. To make the most of the B vitamins contained in foods, they should not be overcooked. It is best to steam vegetables, rather than boil or simmer them.

Supplemental sources

B vitamins are generally best taken in balanced complement, unless there is a specific deficiency or need for an individual vitamin. An excess of one component may lead to depletion of the others. Injectable and oral forms of supplements are available. The injectable types may be more useful for those with deficiencies due to problems with absorption. B complex products vary in terms of components and dose level contained within them.

Individual components are also available as supplements. These are best used with the advice of a health care professional. Some are valuable when addressing specific problems such as pernicious anemia. Strict vegetarians will need to incorporate a supplemental source of B₁₂ in their diets .

Precautions

In many cases, large doses of water-soluble vitamins can be taken with no ill effects since excessive amounts are readily excreted. However, liver inflammation may occur when niacin is taken at daily doses of over 500 mg. This problem occurs more often at doses six times as high. It is generally reversible once the supplementation is stopped. Niacin may also cause difficulty in controlling blood sugar in diabetics. It can increase uric acid levels, which will aggravate gout . Those with ulcers could be adversely affected, as niacin increases the production of stomach acid. Niacin also lowers blood pressure due to its vasodilatory effect, so it should not be taken in conjunction with medications that treat high blood pressure. If a form of niacin known as inositol hexaniacinate is taken, the beneficial effects on cholesterol are maintained without incurring the problems of flushing, gout, and ulcers.

High doses of pyridoxine may cause liver inflammation or permanent nerve damage. Megadoses of this vitamin are not necessary or advisable.

Thoseon medications for seizures, high blood pressure, and Parkinson's disease are at increased risk for interactions. Persons who have chronic health conditions, or take other medications, should seek the advice of a health professional before beginning any program of supplementation.

Side effects

In large amounts, niacin commonly causes flushing and headache , although this can be avoided by taking it in the form of inositol hexaniacinate. Large doses of riboflavin result in very bright yellow urine.

Interactions

Some medications may be affected by B vitamin supplementation, including those prescribed for high blood pressure; Parkinson's disease (such as levodopa, which is inactivated by pantothenic acid); and epileptiform conditions. Folic acid interacts with Dilantin (a brand name for phenytoin sodium ), as well as other anticonvulsants. Large amounts of vitamin C taken within an hour of vitamin B supplements will destroy the cobalamin component. Niacin may interfere with control of blood sugar in people on antidiabetic drugs. Isoniazid, a medication to treat tuberculosis , can impair the proper production and utilization of niacin. Antibiotics potentially decrease the level of some B vitamins by killing the digestive tract bacteria that produce them.

Resources

BOOKS

Bratman, Steven, and David Kroll. Natural Health Bible. CA Prima Publishing, 1999.

Feinstein, Alice. Prevention's Healing with Vitamins. PA: Rodale Press, 1996.

Griffith, H. Winter. Vitamins, Herbs, Minerals & Supplements: The Complete Guide. AZ: Fisher Books, 1998.

Janson, Michael. The Vitamin Revolution in Health Care. Arcadia Press, 1996.

Jellin, Jeff, Forrest Batz, and Kathy Hitchens. Pharmacist's letter/Prescriber's Letter Natural Medicines Comprehensive Database. CA: Therapeutic Research Faculty, 1999.

Pressman, Alan H., and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals. New York: Alpha Books, 1997.

PERIODICALS

Wolters M., A. Strohle, and A. Hahn. "Age-associated changes in the metabolism of vitamin B₁₂ and folic acid: Prevalence, aetiopathogenesis and pathophysiological consequences." Z Gerontol Geriatr. 2004 Apr;37(2):109-35. (article in German, reviewed in abstract only

Balasa, W., K. A. Kalinyak, J. A. Bean, et al. "Hyperhomocysteinemia is Associated with Low Plasma Pyridoxine Levels in Children with Sickle Cell Disease." Journal of Pediatric Hematology and Oncology 24 (June-July 2002): 374-9.

Fairfield, K. M., and R. H. Fletcher. "Vitamins for ChronicDisease Prevention in Adults: Scientific Review." Journal of the American Medical Association (JAMA) 287 (June 19, 2002): 3116-26.

McCaddon, A., B. Regland, P. Hudson, and G. Davies. "Functional Vitamin B₁₂ Deficiency and Alzheimer's Disease." Neurology 58 (May 14, 2002): 1395-9.

Miller, J. W., R. Green, D. M. Mungas, et al. "Homocysteine, Vitamin B₆, and Vascular Disease in AD Patients." Neurology 58 (May 28, 2002): 1449-50.

Morris, M. S. "Folate, Homocysteine, and Neurological Function." Nutrition in Clinical Care 5 (May-June 2002): 124-32.

Prescott, N. J., and S. Malcolm. "Folate and the Face: Evaluating the Evidence for the Influence of Folate Genes on Craniofacial Development." The Cleft Palate-Craniofacial Journal 39 (May 2002): 327-31.

Ulrich, C. M., K. Robien, and R. Sparks. "Pharmacogenetics and Folate Metabolis—A Promising Direction." Pharmacogenomics 3 (May 2002): 299-313.

ORGANIZATIONS

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

Rebecca J. Frey, Ph.D.

Samuel Uretsky, Pharm.D.

Vitamin B complex

Description

Vitamin B complex is a set of 12 related water-soluble substances. Eight are considered vitamins , by virtue of needing to be included in the diet, and four are not, as the body can synthesize them. Since they are water-soluble, most are not stored to any great extent and must be replenished on a daily basis. The eight vitamins have both names and corresponding numbers. They are B₁ (thiamin), B₂ (riboflavin ), B₃ (niacin ), B₅ (pantothenic acid), B₆ (pyridoxine), B₇ (biotin ), B₉ (folic acid ), and B₁₂ (cobalamin). Biotin in particular is not always included in B complex supplements. The numbers that appear to have been skipped were found to be duplicate substances or non-vitamins. The four unnumbered components of B complex that can be synthesized by the body are choline, inositol, PABA, and lipoic acid. As a group, the B vitamins have a broad range of functions. These include maintenance of myelin, which is the covering of nerve cells. A breakdown of myelin can cause a large and devastating variety of neurologic symptoms. B vitamins are also key to producing energy from the nutrients that are consumed. Three members of this group—folic acid, pyridoxine, and cobalamin—work together to keep homocysteine levels low. This is quite important, since high homocysteine levels are associated with heart disease. Some B vitamins prevent certain birth defects (like neural tube defects), maintain healthy red blood cells, support immune function, regulate cell growth, aid in production of hormones, and may have a role in preventing some types of cancer . They also function in maintenance of healthy skin, hair, and nails.

General use

There are many claims for usefulness of various B vitamins. Thiamine is thought to be supportive for people with Alzheimer's disease . Niacin at very high doses is useful to lower cholesterol, and balance high-density (HDL) and low-density (LDL) lipoproteins. This should be done under medical supervision only. Some evidence shows that niacin may prevent juvenile diabetes (type I insulin dependent) in children at risk. It may also maintain pancreatic excretion of some insulin for a longer time than would occur normally. Niacin has also been used to relieve intermittent claudication and osteoarthritis , although the dose used for the latter risks liver problems. The frequency of migraines may be significantly reduced, and the severity decreased, by the use of supplemental riboflavin. Pyridoxine is used therapeutically to lower the risk of heart disease, and to relieve nausea associated with morning sickness and to treat premenstrual syndrome (PMS). In conjunction with magnesium, pyridoxine may have some beneficial effects on the behavior of children with autism. Cobalamin supplementation has been shown to improve male fertility. Folic acid may reduce the odds of cervical or colon cancer in certain at risk groups.

KEY TERMS

Homocysteine —An amino acid produced from the metabolization of other amino acids High levels are an independent risk factor for heart disease.

Macrocytic anemia —A condition caused by cobalamin deficiency, which is characterized by red blood cells that are too few, too fragile, and abnormally large.

Neural tube defect —Incomplete development of the brain, spinal cord, or vertebrae of a fetus, which is sometimes caused by a folic acid deficiency.

Vasodilatory —Causing the veins in the body to dilate, or enlarge.

Vegan —A person who doesn't eat any animal products, including dairy and eggs.

Deficiency

Vitamin B complex is most often used to treat deficiencies that are caused by poor vitamin intake, difficulties with vitamin absorption, or conditions causing increased metabolic rate such as hyperthyroidism that deplete vitamin levels at a higher than normal rate.

Biotin and pantothenic acid are rarely deficient since they are broadly available in food, but often those lacking in one type of B vitamin are lacking in other B components as well. An individual may be symptomatic due to an inadequate level of one vitamin but be suffering from an undetected underlying deficiency as well. One possibility of particular concern is that taking folic acid supplements can cover up symptoms of cobalamin deficiency. This scenario could result in permanent neurologic damage if the cobalamin shortage remains untreated.

Some of the B vitamins have unique functions within the body that allow a particular deficiency to be readily identified. Often, however, they work in concert so symptoms due to various inadequate components may overlap. In general, poor B vitamin levels will cause profound fatigue and an assortment of neurologic manifestations, which may include weakness, poor balance, confusion, irritability, memory loss, nervousness, tingling of the limbs, and loss of coordination. Depression may be an early sign of significantly low levels of pyridoxine and possibly other B vitamins. Additional symptoms of vitamin B deficiency are sleep disturbances, nausea, poor appetite, frequent infections, and skin lesions.

A certain type of anemia (megaloblastic) is an effect of inadequate cobalamin. This anemia can also result if a person stops secreting enough intrinsic factor in the stomach . Intrinsic factor is essential for the absorption of cobalamin. The result of a lack of intrinsic factor is pernicious anemia, so called because it persists despite iron supplementation. Neurologic symptoms often precede anemia when cobalamin is deficient.

A severe and prolonged lack of niacin causes a condition called pellagra. The classic signs of pellagra are dermatitis, dementia , and diarrhea . It is very rare now, except in alcoholics, strict vegans, and people in areas of the world with very poor nutrition .

Thiamine deficiency is similarly rare, save in the severely malnourished and alcoholics. A significant depletion causes a condition known as beriberi, and it can cause weakness, leg spasms, poor appetite, and loss of coordination. Wernicke-Korsakoff syndrome is the most severe form of deficiency, and occurs in conjunction with alcoholism . Early stages of neurologic symptoms are reversible, but psychosis and death may occur if the course is not reversed.

Risk factors for deficiency

People are at higher risk for deficiency if they have poor nutritional sources of B vitamins, take medications or have conditions that impair absorption, or are affected by circumstances that increase the need for vitamin B components above the normal level. Since the B vitamins often work in harmony, a deficiency in one type may have broad implications. Poor intake of B vitamins is most often a problem in strict vegetarians and the elderly. People who frequently fast or diet may also benefit from taking B vitamins. Vegans will need to use brewer's yeast or other sources of supplemental cobalamin, since the only natural sources are meats.

Risk factors that may decrease absorption of some B vitamins include smoking, excessive use of alcohol, surgical removal of portions of the digestive tract, and advanced age. Absorption is also impaired by some medications. Some of the drugs that may cause this are corticosteroids , colchicine, metformin, phenformin, omeprazol, colestipol, cholestyramine, methotrexate, tricyclic antidepressants, and slow-release potassium.

Need for vitamin B complex may be increased by conditions such as pregnancy , breastfeeding, emotional stress , and physical stress due to surgery or injury. People who are very physically active require extra riboflavin. Use of birth control pills also increases the need for certain B vitamins.

Preparations

Natural sources

Fresh meats and dairy products are the best sources for most of the B vitamins, although they are prevalent in many foods. Cobalamin is only found naturally in animal source foods. Freezing of food and exposure to light of food or supplements may destroy some of the vitamin content. Dark-green leafy vegetables are an excellent source of folic acid. To make the most of the B vitamins contained in foods, don't overcook them. It is also best to steam rather than boil or simmer vegetables.

Supplemental sources

B vitamins are generally best taken in balanced complement, unless there is a specific deficiency or need of an individual vitamin. An excess of one component may lead to depletion of the others. Injectable and oral forms of supplements are available. The injectable types may be more useful for those with deficiencies due to problems with absorption. B complex products vary as to which components are included, and at what dose level.

Individual components are also available as supplements. These are best used with the advice of a health care professional. Some are valuable when addressing specific problems such as pernicious anemia. Strict vegetarians will need to incorporate a supplemental source of B₁₂ in the diet.

Precautions

In many cases, large doses of water-soluble vitamins can be taken with no ill effects since excessive amounts are readily excreted. However, when niacin is taken at daily doses of over 500 mg (and more often at doses six times as high), liver inflammation may occur. It is generally reversible once the supplementation is stopped. Niacin may also cause difficulty in controlling blood sugar in diabetics. It can increase uric acid levels that will aggravate gout . Those with ulcers could be adversely affected as niacin increases the production of stomach acid. Niacin also lowers blood pressure due to its vasodilatory effect, so should not be taken in conjunction with medications that are used to treat high blood pressure. If the form of niacin known as inositol hexaniacinate is taken instead, problems with flushing, gout, and ulcers, and liver inflammation do not occur bit beneficial effects on cholesterol are maintained.

High doses of pyridoxine may also cause liver inflammation or permanent nerve damage. Megadoses of this vitamin are not necessary or advisable.

Those on medication for seizures, high blood pressure, and Parkinson's disease are at increased risk for interactions. Any person with a chronic health condition, or taking other medications should seek the advice of a health professional before beginning any program of supplementation.

Side effects

Niacin in large amounts commonly causes flushing and headache, although this can be circumvented by taking it in the form of inositol hexaniacinate. Large doses of riboflavin make the urine turn very bright yellow.

Interactions

Some medications may be affected by B vitamin supplementation, including those for high blood pressure, Parkinson's disease (such as levodopa, which is inactivated by pantothenic acid) and epileptiform conditions. Folic acid interacts with Dilantin as well as other anticonvulsants. Large amounts of vitamin C taken within an hour of vitamin B supplements will destroy the cobalamin component. Niacin may interfere with control of blood sugar in people on antidiabetic drugs . Isoniazid, a medication to treat tuberculosis , can impair the proper production and utilization of niacin. Antibiotics potentially decrease the level of some B vitamins by killing the bacteria in the digestive tract that produce them.

Resources

BOOKS

Bratman, Steven and David Kroll. Natural Health Bible. CA: Prima Publishing, 1999.

Feinstein, Alice. Prevention's Healing with Vitamins. PA: Rodale Press, 1996.

Griffith, H. Winter. Vitamins, Herbs, Minerals & Supplements: The Complete Guide. AZ: Fisher Books, 1998.

Janson, Michael. The Vitamin Revolution in Health Care. Arcadia Press, 1996.

Jellin, Jeff, Forrest Batz, and Kathy Hitchens. Pharmacist's letter/Prescriber's Letter Natural Medicines Comprehensive Database. CA: Therapeutic Research Faculty, 1999.

Pressman, Alan H. and Sheila Buff. The Complete Idiot's Guide to Vitamins and Minerals. New York: Alpha Books, 1997.

Judith Turner

Vitamin B Complex

Description

Vitamin B complex is a set of 12 related water-soluble substances. Eight are considered vitamins, by virtue of needing to be included in the diet, and four are not, as the body can synthesize them. Since they are water-soluble, most are not stored to any great extent and must be replenished on a daily basis. The eight vitamins have both names and corresponding numbers. They are B₁ (thiamin), B₂ (riboflavin ), B₃ (niacin ), B₅ (pantothenic acid), B₆ (pyridoxine), B₇ (biotin ), B₉ (folic acid ), and B₁₂ (cobalamin). Biotin in particular is not always included in B complex supplements. The numbers that appear to have been skipped were found to be duplicate substances or non-vitamins. The four unnumbered components of B complex that can be synthesized by the body are choline, inositol, PABA, and lipoic acid. As a group, the B vitamins have a broad range of functions. These include maintenance of myelin, which is the covering of nerve cells. A breakdown of myelin can cause a large and devastating variety of neurologic symptoms. B vitamins are also key to producing energy from the nutrients that are consumed. Three members of this group—folic acid, pyridoxine, and cobalamin—work together to keep homocysteine levels low. This is quite important, since high homocysteine levels are associated with heart disease. Some B vitamins prevent certain birth defects (like neural tube defects), maintain healthy red blood cells, support immune function, regulate cell growth, aid in production of hormones, and may have a role in preventing some types of cancer. They also function in maintenance of healthy skin, hair, and nails.

General use

There are many claims for usefulness of various B vitamins. Thiamine is thought to be supportive for people with Alzheimer's disease. Niacin at very high doses is useful to lower cholesterol, and balance high-density (HDL) and low-density (LDL) lipoproteins. This should be done under medical supervision only. Some evidence shows that niacin may prevent juvenile diabetes (type I insulin dependent) in children at risk. It may also maintain pancreatic excretion of some insulin for a longer time than would occur normally. Niacin has also been used to relieve intermittent claudication and osteoarthritis, although the dose used for the latter risks liver problems. The frequency of migraines may be significantly reduced, and the severity decreased, by the use of supplemental riboflavin. Pyridoxine is used therapeutically to lower the risk of heart disease, and to relieve nausea associated with morning sickness and to treat premenstrual syndrome (PMS). In conjunction with magnesium, pyridoxine may have some beneficial effects on the behavior of children with autism. Cobalamin supplementation has been shown to improve male fertility. Folic acid may reduce the odds of cervical or colon cancer in certain at risk groups.

Deficiency

Vitamin B complex is most often used to treat deficiencies that are caused by poor vitamin intake, difficulties with vitamin absorption, or conditions causing increased metabolic rate such as hyperthyroidism that deplete vitamin levels at a higher than normal rate.

Biotin and pantothenic acid are rarely deficient since they are broadly available in food, but often those lacking in one type of B vitamin are lacking in other B components as well. An individual may be symptomatic due to an inadequate level of one vitamin but be suffering from an undetected underlying deficiency as well. One possibility of particular concern is that taking folic acid supplements can cover up symptoms of cobalamin deficiency. This scenario could result in permanent neurologic damage if the cobalamin shortage remains untreated.

Some of the B vitamins have unique functions within the body that allow a particular deficiency to be readily identified. Often, however, they work in concert so symptoms due to various inadequate components may overlap. In general, poor B vitamin levels will cause profound fatigue and an assortment of neurologic manifestations, which may include weakness, poor balance, confusion, irritability, memory loss, nervousness, tingling of the limbs, and loss of coordination. Depression may be an early sign of significantly low levels of pyridoxine and possibly other B vitamins. Additional symptoms of vitamin B deficiency are sleep disturbances, nausea, poor appetite, frequent infections, and skin lesions.

A certain type of anemia (megaloblastic) is an effect of inadequate cobalamin. This anemia can also result if a person stops secreting enough intrinsic factor in the stomach. Intrinsic factor is essential for the absorption of cobalamin. The result of a lack of intrinsic factor is pernicious anemia, so called because it persists despite iron supplementation. Neurologic symptoms often precede anemia when cobalamin is deficient.

A severe and prolonged lack of niacin causes a condition called pellagra. The classic signs of pellagra are dermatitis, dementia, and diarrhea. It is very rare now, except in alcoholics, strict vegans, and people in areas of the world with very poor nutrition.

Thiamine deficiency is similarly rare, save in the severely malnourished and alcoholics. A significant depletion causes a condition known as beriberi, and it can cause weakness, leg spasms, poor appetite, and loss of coordination. Wernicke-Korsakoff syndrome is the most severe form of deficiency, and occurs in conjunction with alcoholism. Early stages of neurologic symptoms are reversible, but psychosis and death may occur if the course is not reversed.

Risk factors for deficiency

People are at higher risk for deficiency if they have poor nutritional sources of B vitamins, take medications or have conditions that impair absorption, or are affected by circumstances that increase the need for vitamin B components above the normal level. Since the B vitamins often work in harmony, a deficiency in one type may have broad implications. Poor intake of B vitamins is most often a problem in strict vegetarians and the elderly. People who frequently fast or diet may also benefit from taking B vitamins. Vegans will need to use brewer's yeast or other sources of supplemental cobalamin, since the only natural sources are meats.

Risk factors that may decrease absorption of some B vitamins include smoking, excessive use of alcohol, surgical removal of portions of the digestive tract, and advanced age. Absorption is also impaired by some medications. Some of the drugs that may cause this are corticosteroids, colchicine, metformin, phenformin, omeprazol, colestipol, cholestyramine, methotrexate, tricyclic antidepressants, and slow-release potassium.

Need for vitamin B complex may be increased by conditions such as pregnancy, breastfeeding, emotional stress, and physical stress due to surgery or injury. People who are very physically active require extra riboflavin. Use of birth control pills also increases the need for certain B vitamins.

Preparations

Natural sources

Fresh meats and dairy products are the best sources for most of the B vitamins, although they are prevalent in many foods. Cobalamin is only found naturally in animal source foods. Freezing of food and exposure of food or supplements to light may destroy some of the vitamin content. Dark-green leafy vegetables are an excellent source of folic acid. To make the most of the B vitamins contained in foods, do not overcook them. It is also best to steam rather than boil or simmer vegetables.

Supplemental sources

B vitamins are generally best taken in balanced complement, unless there is a specific deficiency or need of an individual vitamin. An excess of one component may lead to depletion of the others. Injectable and oral forms of supplements are available. The injectable types may be more useful for those with deficiencies due to problems with absorption. B complex products vary as to which components are included, and at what dose level.

Individual components are also available as supplements. These are best used with the advice of a health care professional. Some are valuable when addressing specific problems such as pernicious anemia. Strict vegetarians will need to incorporate a supplemental source of B₁₂ in the diet.

Precautions

In many cases, large doses of water-soluble vitamins can be taken with no ill effects since excessive amounts are readily excreted. However, when niacin is taken at daily doses of over 500 mg (and more often at doses six times as high), liver inflammation may occur. It is generally reversible once the supplementation is stopped. Niacin may also cause difficulty in controlling blood sugar in diabetics. It can increase uric acid levels that will aggravate gout. Those with ulcers could be adversely affected as niacin increases the production of stomach acid. Niacin also lowers blood pressure due to its vasodilatory effect, so should not be taken in conjunction with medications that are used to treat high blood pressure. If the form of niacin known as inositol hexaniacinate is taken instead, problems with flushing, gout, ulcers, and liver inflammation do not occur but beneficial effects on cholesterol are maintained.

High doses of pyridoxine may also cause liver inflammation or permanent nerve damage. Megadoses of this vitamin are not necessary or advisable.

Those on medication for seizures, high blood pressure, and Parkinson's disease are at increased risk for interactions. Any person with a chronic health condition or taking other medications should seek the advice of a health professional before beginning any program of supplementation.

Side effects

Niacin in large amounts commonly causes flushing and headache, although this can be circumvented by taking it in the form of inositol hexaniacinate. Large doses of riboflavin make the urine turn very bright yellow.

Interactions

Some medications may be affected by B vitamin supplementation, including those for high blood pressure, Parkinson's disease (such as levodopa, which is inactivated by pantothenic acid) and epileptiform conditions. Folic acid interacts with Dilantin as well as other anticonvulsants. Large amounts of vitamin C taken within an hour of vitamin B supplements will destroy the cobalamin component. Niacin may interfere with control of blood sugar in people on antidiabetic drugs. Isoniazid, a medication to treat tuberculosis, can impair the proper production and utilization of niacin. Antibiotics potentially decrease the level of some B vitamins by killing the bacteria in the digestive tract that produce them.

KEY TERMS

Homocysteine— An amino acid produced from the metabolization of other amino acids. High levels are an independent risk factor for heart disease.

Macrocytic anemia— A condition caused by cobalamin deficiency, which is characterized by red blood cells that are too few, too fragile, and abnormally large.

Neural tube defect— Incomplete development of the brain, spinal cord, or vertebrae of a fetus, which is sometimes caused by a folic acid deficiency.

Vasodilatory— Causing the veins in the body to dilate, or enlarge.

Vegan— A person who does not eat any animal products, including dairy and eggs.

Resources

BOOKS

Bratman, Steven, and David Kroll. Natural Health Bible. Prima Publishing, 1999.

Feinstein, Alice. Prevention's Healing with Vitamins. Rodale Press, 1996.

Griffith, H. Winter. Vitamins, Herbs, Minerals & Supplements: The Complete Guide. Fisher Books,1998.

Janson, Michael. The Vitamin Revolution in Health Care. Arcadia Press, 1996.

Jellin, Jeff, Forrest Batz, and Kathy Hitchens. Pharmacist's Letter/Prescriber's Letter Natural Medicines Comprehensive Database. Therapeutic Research Faculty, 1999.

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vitamin B complex A group of water-soluble vitamins that characteristically serve as components of coenzymes. Plants and many microorganisms can manufacture B vitamins but dietary sources are essential for most animals. Heat and light tend to destroy B vitamins.

Vitamin B₁ (thiamin(e)) is a precursor of the coenzyme thiamine pyrophosphate, which functions in carbohydrate metabolism. Deficiency leads to beriberi in humans and to polyneuritis in birds. Good sources include brewer's yeast, wheatgerm, beans, peas, and green vegetables.

Vitamin B₂ (riboflavin) occurs in green vegetables, yeast, liver, and milk. It is a constituent of the coenzymes FAD and FMN, which have an important role in the metabolism of all major nutrients as well as in the oxidative phosphorylation reactions of the electron transport chain. Deficiency of B₂ causes inflammation of the tongue and lips and mouth sores.

Vitamin B₆ (pyridoxine) is widely distributed in cereal grains, yeast, liver, milk, etc. It is a constituent of a coenzyme (pyridoxal phosphate) involved in amino acid metabolism. Deficiency causes retarded growth, dermatitis, convulsions, and other symptoms.

Vitamin B₁₂ (cyanocobalamin or cobalamin) is manufactured only by microorganisms and natural sources are entirely of animal origin. Liver is especially rich in it. One form of B₁₂ functions as a coenzyme in a number of reactions, including the oxidation of fatty acids and the synthesis of DNA. It also works in conjunction with folic acid (another B vitamin) in the synthesis of the amino acid methionine and it is required for normal production of red blood cells. Vitamin B₁₂ can only be absorbed from the gut in the presence of a glycoprotein called intrinsic factor; lack of this factor or deficiency of B₁₂ results in pernicious anaemia.

Other vitamins in the B complex include nicotinic acid, pantothenic acid, biotin, and lipoic acid. See also choline; inositol.

vitamin B n. any one of a group of water-soluble vitamins that are often found together in the same kinds of food, such as liver, yeast, and eggs, and all function as coenzymes. B₁ (thiamin, aneurine) a vitamin deficiency of which leads to beriberi. Recommended daily intake: 1 mg. B₂ (riboflavin) a vitamin important in tissue respiration. A deficiency causes ariboflavinosis. Recommended daily intake: 1.7 mg. B₆ (pyridoxine) a vitamin from which the coenzyme pyridoxal phosphate is formed. Deficiency is very rare. B₁₂ (cyanocobalamin) a vitamin that can be absorbed only in the presence of intrinsic factor, secreted in the stomach. A deficiency can lead to pernicious anaemia and degeneration of the nervous system. Recommended daily intake: 3–4 μg. See also biotin, folic acid, nicotinic acid, pantothenic acid.