Home > Encyclopedia of Nursing & Allied Health > 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.

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KEY TERMS

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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.

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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.

Judith Turner