The Role of B Vitamins

Water-soluble vitamins were collectively called water soluble B in the beginning. When more water-soluble vitamins were discovered, they were referred to as B1, B2, B6, B12 and so on. Later when more vitamins were discovered in both the categories, they were referred as vitamins C, D, E and K. Now, most are known by a word that indicates either chemical nature or function.

Some vitamins are synthesized in the body itself by intestinal micro-organisms. Antibiotics and sulfa drugs may destroy these organisms resulting in decreased vitamin synthesis. There are other bacteria which when present in the intestine utilize dietary vitamins for their own use thus causing vitamin deficiency.
Vitamins in the diet are bound to protein and fat. During digestion, they get broken down and absorbed. Vitamins present in undigested food are not available to the body. The body requirement of vitamins depends upon several factors. Apart from those mentioned above, people suffering from tuberculosis or high fever require more vitamins and people living in high altitudes and cold regions also have increased vitamin requirement.

The B vitamins have a wide and varied range of functions in the human body. Most B vitamins are involved in the process of converting blood sugar into energy. Diets rich in B vitamins are particularly important for pregnant and breast-feeding women and for other people who require more energy, such as athletes and heavy-labor workers.

General Deficiencies of Vitamin B
Deficiencies of B vitamins are uncommon in the U.S., but when they occur, they usually involve several B vitamins, since many of them come from the same food groups. Alcohol interferes with these vitamins, and some of the physical and mental problems that alcoholics experience may be attributed to a deficiency of B vitamins. Elderly people are also at risk for deficiencies, because of inadequate diets and potential interference with B-vitamin absorption by medications.

General Toxicity of Vitamin B
Because the B vitamins are water-soluble and eliminated in the urine, toxic reactions from oral administration of most of them are extremely rare. (Exceptions are niacin and B6.) (For specific adverse reactions from deficiencies or high dosage levels, see individual discussions of B vitamins, below). It should be noted that substances known as B15 (pangamic acid) and B17 (laetrile) are neither vitamins nor nutrients; both chemicals are highly dangerous and have no proven nutritional or other value.

Deficiencies and Toxicity of Vitamin B1 (Thiamin)
Thiamin is essential for converting blood sugar into energy and is involved in metabolic activities in nerves, heart, and muscles and in the production of red blood cells. Thiamin is found in almost all foods, but the best source is pork and good sources are dried fortified cereals, oatmeal, corn, nuts, cauliflower, and sunflower seeds. Recommended RDA is 1.2 mg per day for men and 1.1 mg for women. Supplements for people with normal diets and health are unnecessary. Severe vitamin B1 deficiency, known as beriberi, is rare in the U.S., but can occur in alcoholics, in severely malnourished people, or in those receiving long-term dialysis or intravenous feeding. Symptoms may include visual disturbances, paralysis, staggering, loss of sensation in the legs and feet, psychosis, and congestive heart failure. No toxic effects have been reported for thiamin.

Deficiencies and Toxicity of Vitamin B2 (Riboflavin)
Like thiamin, riboflavin is important in the production of energy. Some dietary sources are liver, dried fortified cereals, and low fat yogurt. Recommended DRI is 1.7 mg. Supplements for people with normal diets and health are unnecessary. Deficiencies affect the skin and mucous membranes and can cause cracks on the lips or corners of the mouth, eczema of the face and genitals, a burning sensation on the tongue, or eye irritation. Previously, no toxic effects had been reported even from large doses of riboflavin However, one new study indicated that high consumption of vitamin B2 may increase the risk of stomach cancer. (In the same study, vitamins B1, B3, and B6 were protective).

Deficiencies and Toxicity of Vitamin B3 (Niacin)
Niacin, also known as nicotinic acid, helps break down blood sugar for energy and also acts as a vasodilator, widening blood vessels and increasing blood flow. Dietary sources are mackerel, swordfish, chicken, veal, dried fortified cereals, pork, salmon, and beef liver. Current DRI recommendations are 20 mg. This vitamin may be prescribed for improving cholesterol levels, but supplements