14.10: Summary

There are nine water-soluble vitamins—eight B-vitamins and vitamin C. The B-vitamins are components of various coenzymes important in metabolism.

Vitamin C is used by the body to form connective tissue, bone, and capillaries. It also facilitates the body’s use of calcium and iron, helps immune function and hormone production, and it serves as an antioxidant. A severe deficiency of vitamin C leads to scurvy, which was once thought to be a contagious disease. Most Americans get enough vitamin C in their diets.

Thiamin prevents the deficiency disease beriberi. It’s part of a coenzyme used in energy production, but consuming extra thiamin won’t make one more “energetic.” Wernicke-Korsakoff Syndrome is a degenerative disease of the brain related to thiamin deficiency, and is most commonly seen in alcoholics.

Riboflavin is part of another coenzyme that aids energy production. Deficiencies are uncommon, and usually accompany severe malnutrition that includes deficiencies of other B vitamins (riboflavin also helps niacin and B₆ function). A riboflavin deficiency alone doesn’t normally result in just one symptom (e.g., hair loss).

Niacin, like thiamin and riboflavin, is part of a coenzyme that aids energy production. Severe deficiency causes pellagra. The body can make niacin from the amino acid tryptophan, so the need for niacin is related to how much protein is in the diet.

Vitamin B6 coenzymes are needed in amino acid metabolism, e.g., helping make “non-essential” amino acids, removing amino groups to allow amino acids to be used for energy, and converting tryptophan into niacin.

Folate is part of a coenzyme needed to make DNA and RNA, making it crucial in cell division. A deficiency symptom is anemia, but deficiencies are less common now that folate is added to enriched grains. Needs are higher during pregnancy; a deficiency in early pregnancy increases the risk of neural tube defects in the newborn. All women of child-bearing age are advised to get enough folate from fortified foods or vitamin pills.

B₁₂ is the only B vitamin not made by plants. It’s also unique as a B-vitamin because the body can store up to about 4 years’ worth. Intrinsic factor, secreted by the stomach, is needed for B₁₂ absorption. A lack of intrinsic factor (from a loss of the stomach cells that make it) prevents the absorption of B₁₂ from the diet, in which case B₁₂ can be given by injection.

Vegans (and infants born of vegan mothers) are at risk for B₁₂ deficiency, since B₁₂ is found naturally only in animal-based foods (e.g., meat, dairy). Vegans should make sure they get enough B₁₂, either as a supplement or by eating foods fortified with B₁₂.

A deficiency of B₁₂ can also occur in those over age 50, due in part from less stomach acid. The acid helps release food-bound B₁₂. To over-ride this problem, those over age 50 are advised to get B₁₂ from fortified foods or vitamin pills.

Large amounts of folate given to those who are B₁₂ deficient will alleviate the B₁₂ deficiency anemia but won’t do anything about the nerve damage that also can result from B₁₂ deficiency. This “masking” of the anemia caused by a B₁₂ deficiency can delay the diagnosis, risking permanent nerve damage.

Pantothenic acid is found in almost every food, so deficiencies are nearly impossible without severe malnutrition. Its role is as a part of Coenzyme A, which plays a crucial role in energy metabolism.

Biotin is provided by our intestinal bacteria, and deficiencies usually accompany only severe malnutrition. Biotin also has a role in producing energy, fatty acids and amino acids.

For continually updated fact sheets on individual vitamins, go to the website of our Office of Dietary Supplements. ods.od.nih.gov/factsheets