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, reviewed by
Kimberly Langdon M.D.
Zinc is a catalyst for many different enzyme reactions required by the body. It also helps to regulate thyrotropin-releasing hormone (TRH) and thyroid-stimulating hormone (TSH). Zinc may become depleted in those with hypothyroidism who overproduce TSH. When TSH is high, it may be a sign that the body is under producing the thyroid hormones, thyroxine (T4) and triiodothyronine (T3). So, proper concentrations of zinc are needed to support the production of thyroid hormone.
Zinc is essential for overall immune function by regulating the communication between immune cells. Balanced zinc concentrations help protect the body against autoimmune diseases, chronic inflammation, or allergies. One double-blind study in The Journal of Infectious Diseases recruited 50 volunteers within 24 hours of developing symptoms of the common cold. Each participant was randomly assigned to receive zinc or a placebo every few hours. Compared to the placebo group, the group treated with zinc had reduced the duration and severity of cold symptoms, including cough and nasal discharge.
Intestinal permeability (a.k.a leaky gut) is often associated with an autoimmune disease like Hashimoto’s thyroiditis. Typically, there is a tight seal between adjacent intestinal cells to keep pathogens from entering the bloodstream. It’s important to maintain the integrity of this seal to protect the body from antigens and bacteria “leaking." However, zinc deficiency can lead to inflammation, which can weaken this barrier. Supplementing with zinc may help to tighten the intestinal junctions.
Consuming too much zinc can cause toxicity. Zinc toxicity symptoms include nausea and vomiting, loss of appetite, diarrhea, abdominal cramps, and headaches. The Tolerable Upper Intake Level (UL)—defined as the highest daily intake level that is likely to pose no adverse health effects—for adults is 40 mg per day. However, this UL does not apply to people with zinc deficiencies, who may need to take higher-dose supplements.
Research shows that consuming too much zinc (150-450 mg of zinc per day) can also interfere with the absorption of other nutrients like copper or iron, causing deficiencies in those nutrients.
Zinc supplements may interact with several medications like antibiotics, penicillamine, and diuretics. People who take these medications regularly should talk to their doctor about zinc supplementation.
The Recommended Dietary Allowance (RDA) of zinc—or, the average daily level of intake sufficient to meet the nutrient requirements of nearly all healthy individuals—is 11 mg for adult men and 8 mg for adult women. Pregnant and breastfeeding women should consume 11 and 12 mg per day, respectively.
A zinc deficiency can compromise wound healing as this micronutrient plays an essential role in every phase of the wound healing process. It plays a role in everything from cell membrane repair to oxidative stress, blood clotting to immune response, tissue repair to the development of new blood vessels, and scar formation. However, it's not entirely clear HOW zinc does all these functions. Supplementing with zinc can help accelerate healing in people with wounds.
Several studies show that zinc can reduce the severity and duration of cold symptoms when taken as a zinc-containing lozenge or zinc-containing syrup that "sticks" in the mouth and throat. These forms allow zinc to make contact with the rhinovirus in those areas.
Many foods contain zinc—oysters more so than any other food, but red meat and poultry are excellent sources, too. Other good dietary sources of zinc include beans, nuts, crab and lobster, whole grains, fortified breakfast cereals, and dairy products. Phytic acid, or phytate, is found in plant seeds and inhibits the absorption of zinc. So, the bioavailability of zinc from plant foods may be slightly lower than that of animal foods.