Zinc is an essential mineral that is found in every cell in our body. It stimulates the activity of about 100 enzymes, substances that promote biochemical reactions in your body. Among its many functions, zinc maintains a healthy immune system, is needed for wound healing, helps maintain your sense of taste and smell, and is needed for DNA synthesis. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence, and helps sperm develop and is needed for ovulation and fertilization.

Taking lozenges made of zinc gluconate can help shorten the length of a cold. Most forms of zinc work equally well, but if you're trying to prevent a cold, use zinc lozenges or a zinc spray made of zinc gluconate. Take 15 mg of zinc daily (the amount in most multivitamins). Because zinc can block copper absorption, make sure that your supplement also contains 1 to 2 mg of copper.

To fight colds, use a zinc nasal spray four times a day or suck on zinc lozenges that contain 15 to 25 mg of zinc gluconate every two to four hours as soon as you notice symptoms. Stop when symptoms subside. Consuming zinc on an empty stomach can cause nausea, so take zinc supplements with food.

Zinc deficiency most often happens when its intake is inadequate or it is poorly absorbed, when there are increased losses of zinc from the body, or when the body’s requirement for zinc increases. Zinc deficiency manifests as growth retardation, hair loss, diarrhea, delayed sexual maturation and impotence, eye and skin lesions, and loss of appetite.
Weight loss, delayed healing of wounds, taste abnormalities, and mental lethargy can also occur in zinc deficiency. Since many of these symptoms are general and are associated with other medical conditions, do not assume they are due to a zinc deficiency without consulting your doctor.

Risk factors for zinc deficiency include: inadequate caloric intake, alcoholism, and digestive diseases. Vegetarians may need as much as 50% more zinc than non-vegetarians because of the lower absorption of zinc from plant foods, so they need to have good sources of zinc in their diet.

Maternal zinc deficiency can slow fetal growth. Growth rate improves in children with mild to moderate growth failure and who also have a zinc deficiency when given zinc. Human milk does not have enough zinc for older infants between the ages of 7 months and 12 months, so breast-fed infants of this age should also consume age-appropriate foods containing zinc or be given formula containing zinc or zinc supplementation.

Breastfeeding also may deplete maternal zinc stores because of the greater need for zinc during lactation. Include good sources of zinc in your daily diet if you are breast-feeding.

30% to 50% of alcoholics are zinc deficient. Alcohol decreases the absorption of zinc and increases loss of zinc in urine. Further, many alcoholics do not eat an acceptable variety or amount of food, so their dietary intake of zinc may be inadequate.

Diarrhea causes zinc loss. Those who have had gastrointestinal surgery or who have digestive disorders that result in malabsorption, including sprue, Crohn’s disease and short bowel syndrome, may lack zinc. Take additional zinc if you have any of these problems.

Zinc deficiency compromises your immune system. Zinc is required for the development and activation of T-lymphocytes, a kind of white blood cell that helps fight infection. When zinc supplements are given to individuals with low zinc levels, the numbers of T-cell lymphocytes circulating in the blood increase and the ability of lymphocytes to fight infection improves.

The effect of zinc treatments on the severity or duration of cold symptoms is controversial. A study of over 100 employees of the Cleveland Clinic indicated that zinc lozenges decreased the duration of colds by one-half, although no differences were seen in how long fevers lasted or the level of muscle aches. Other studies examined the effect of zinc supplements on cold duration and severity in over 400 randomized subjects. In their first study, a virus was used to induce cold symptoms. The duration of illness was much shorter in the group receiving zinc gluconate lozenges (providing 13.3 mg zinc) but not in the group receiving zinc acetate lozenges (providing 5 or 11.5 mg zinc).

Some researchers have questioned the effect of iron fortification, to prevent iron-deficiency anemia, on absorption of other nutrients, including zinc. Fortification of foods with iron does not significantly affect zinc absorption. However, large amounts of iron in supplements (greater than 25 mg) may decrease zinc absorption, as can iron in solutions. Taking iron supplements between meals will help decrease its effect on zinc absorption.

Zinc toxicity has been seen in both acute and chronic forms. Intakes of 150 to 450 mg of zinc per day have been associated with low copper status, altered iron function, reduced immune function, and reduced levels of high-density lipoproteins (the good cholesterol)

References
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2. Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc. National Academy Press. Washington, DC, 2001.

3. Solomons NW. Mild human zinc deficiency produces an imbalance between cell-mediated and humoral immunity. Nutr Rev 1998;56:27-28.

4. Prasad AS. Zinc: An overview. Nutrition 1995;11:93-99.

5. Heyneman CA. Zinc deficiency and taste disorders. Ann Pharmacother 1996;30:186-187.