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B Vitamin Deficiencies

Oct 17, 2010 | By Ruth Coleman, M.D.

The B vitamins perform several important functions in the human body. They have a role in the metabolism of amino acids, carbohydrates and fats. B vitamins are necessary for reactions that take place in the skin, nervous system and blood, and they are vital for the maturation of blood cells. B-vitamin deficiencies, therefore, can have wide-ranging effects.

Vitamin B1: Thiamine

The main food sources of vitamin B1 include beef, pork, whole grains, yeast and nuts. Tea, as well as regular and decaffeinated coffee, can decrease the vitamin levels if consumed in large amounts, according to Robert Russell, M.D., director of the USDA Human Nutrition Research Center on Aging, in "Harrison's Principles of Internal Medicine." The main causes of vitamin B1 deficiency in America are long-term illnesses and alcoholism, says Russell. A deficiency can lead to beriberi, a condition that may cause neurological and heart problems. Alcoholics can develop Wernicke-Korsakoff syndrome, which can cause eye and memory problems and a lack of coordination.

Vitamin B2: Riboflavin

The main sources of vitamin B2 include enriched breads, cereals and dairy products. Legumes, broccoli, fish, lean meat and eggs provide additional sources. People with a vitamin B2 deficiency may have lesions on their lips and develop cracks on the sides of the mouth. They may develop lesions on the skin that look red and scaly. The tongue can become sore and turn a deep purplish-red color. They may have irritated eyes and some may even have personality changes, says Russell.

Vitamin B3: Niacin

The sources of vitamin B3 include eggs, milk, beans, flour, millet and meat. A deficiency of vitamin B3 causes pellagra, and yet many people in India have this disease, even though they eat millet. Millet is a type of cereal, or grain, which is very high in leucine, an amino acid. Because people in India who eat a lot of millet develop pellagra, an imbalance in amino acids is hypothesized to somehow contribute to the development of the disease, explains Larry Johnson, M.D., Ph.D., attending physician at the Central Arkansas Veterans Healthcare System in "The Merck Manual for Healthcare Professionals." Pellagra symptoms include diarrhea, a rash and dementia.

Vitamin B6: Pyridoxine

Because most food has vitamin B6, Johnson says that people usually develop a deficiency from alcoholism; the malabsorption of food; or from taking certain medications, such as anticonvulsants and drugs to treat tuberculosis and steroids. A deficiency of vitamin B6 can cause a skin rash, sore tongue and cracks on the side of the mouth. Adults may also develop confusion, depression and seizures. It is rare, but infants who have a vitamin B6 deficiency can develop seizures.

Vitamin B12: Cobalamin

The only source of vitamin B12 is animal products, which is why strict vegetarians can develop a deficiency, explains David Bender, Ph.D., senior lecturer in biochemistry at the University College of London, in "Harper's Illustrated Biochemistry." A deficiency of this vitamin causes pernicious anemia, which causes people to be anemic and have large, immature red blood cells circulating throughout their bloodstream. People who are not vegetarian can develop pernicious anemia if they have a disorder that causes their immune system to attack the parietal cells of the stomach. A vitamin B12 deficiency can also lead to neurological problems.

References

Article reviewed by Christine Brncik Last updated on: Oct 17, 2010

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