An essential mineral required by every cell in the body, zinc is concentrated in the muscles, bones, skin, kidneys, liver, pancreas, eyes, and, in men, the prostate. It is plentiful in drinking water and in some foods, including meat. Because your body does not produce zinc, it depends on external sources for its supply.
Zinc plays a critical role in hundreds of body processes -- from cell growth to sexual maturation and immunity, even for taste and smell. Consequently, everyone who takes a daily multivitamin and mineral supplement should be certain that it contains zinc. Individual supplements are also available for specific complaints.
Major benefits: Necessary for the proper functioning of the immune system, zinc helps to protect the body against colds, flu, conjunctivitis, and other infections. In a study of 100 people in the initial stages of a cold, those who sucked on zinc lozenges every couple of hours recovered from their illness about three days earlier than those who sucked on placebo lozenges. Zinc lozenges may also speed the healing of canker sores and sore throat. Taken in pill form, zinc may aid in treating more serious illnesses, such as rheumatoid arthritis, lupus, fibromyalgia, and possibly multiple sclerosis, as well as other conditions, such as AIDS, which are associated with an improperly functioning immune system.
Additional benefits: Zinc exerts beneficial effects on various hormones, including the sex and thyroid hormones. It shows promise for enhancing fertility in both women and men. Zinc may also shrink an enlarged prostate. In addition, it may be effective for those with an underactive thyroid and, because it improves insulin levels, it may help people with diabetes.
Because zinc affects so many body systems, it has many other uses. It stimulates the healing of wounds and skin irritations, making it useful for acne, burns, eczema, psoriasis, and rosacea, and promotes the health of the hair and scalp. Zinc has also been shown to slow vision loss in people with macular degeneration, a common cause of blindness in those over age 50. And in a recent Japanese study, tinnitus (ringing in the ears) improved with zinc supplementation. Zinc may also be useful for osteoporosis, hemorrhoids, inflammatory bowel disease, and ulcers.
How much you need: The RDA for zinc is 12 mg for women and 15 mg for men daily. Higher doses are usually reserved for specific complaints.
If you get too little: Severe zinc deficiency is rare in the United States, but a mild zinc deficiency can lead to poor wound healing, more colds and flu, a muted sense of taste and smell, and skin problems such as acne, eczema, and psoriasis. It can result in impaired blood sugar tolerance (and an increased diabetes risk) and a low sperm count.
If you get too much: Long-term use of more than 100 mg a day has been shown to impair immunity and lower the level of HDL ("good") cholesterol. One study reported a connection between excess zinc and Alzheimer's, though evidence is scant. Larger doses (more than 200 mg a day) can cause nausea, vomiting, and diarrhea.
Dosage: The usual dosage is 30 mg once a day. Taking zinc for longer than a month may interfere with copper absorption, so add 2 mg of copper for every 30 mg of zinc. For short-term use (colds or flu), use zinc lozenges every two to four hours for a week; don't exceed 150 mg a day.
Guidelines for use: Take zinc an hour before or two hours after a meal; if it causes stomach upset, have it with a low-fiber food. If you also use iron supplements, do not take them at the same time as zinc. Take zinc at least two hours after taking antibiotics.
Other sources: When looking for foods rich in zinc, think protein. It's abundant in beef, pork, liver, poultry (especially dark meat), eggs, and seafood (especially oysters). Cheese, beans, nuts, and wheat germ are other good sources, but the zinc in these foods is less easily absorbed than the zinc in meat.