Zinc is involved in wound healing, cell reproduction and tissue growth, sexual maturation, and taste and smell. It is also associated with more than 100 enzymatic reactions in the body.

How Much: Recommended dietary allowance (RDA) = 11 mg daily for men; 8 mg daily for women.

Too Much: Tolerable upper limit (UL) = 40 mg daily.

Too Little: Hair loss, eye and skin sores, diarrhea, and loss of appetite.

Foods: Oysters, crab, lobster; red meat, chicken, turkey; zinc-fortified breakfast cereals; beans, nuts, whole grains.

Interactions: Antibiotics, diuretics and calcium.

Research Note: Studies show significantly lower zinc levels in people with rheumatoid arthritis (RA) compared to those without it. The lowest levels are associated with more severe disease. Researchers say zinc may help improve RA symptoms by supporting the immune system and cartilage.