Zinc is an essential mineral that is critical for the function of hundreds of enzymes. Consequently, it plays many roles, including in antioxidant enzymes, brain function, and the immune system. Zinc is most commonly taken to reduce the duration of respiratory infections and the common cold.
Zinc is most often used for
Zinc is an essential mineral and has a multitude of biological roles because it is a functional component of over 300 hundred enzymes that rely on zinc to be able to catalyze chemical reactions. Zinc also participates in the structure of important proteins and is involved in the regulation of gene expression.
Zinc is obtained from the diet. Oysters contain substantially more zinc than any other food, although red meat (e.g., beef, pork) and poultry provide the majority of zinc in the American diet. Other good sources of zinc are legumes, nuts, and dairy products. In some countries, the flours used in cereals are fortified with zinc.
The potential benefits of supplementation with zinc are largely dependent on the individual’s zinc status. Therefore, supplementation with zinc is unlikely to provide a benefit if zinc levels are already adequate and the person is not zinc deficient. One exception to this rule may be respiratory tract infections and the common cold, conditions in which supplementation with zinc has been shown to reduce the duration of illness. In children, zinc may help prevent pneumonia. However, further high-quality studies are needed to bolster the evidence in this field.
Supplementation with zinc has been shown to improve depressive symptoms and markers of glycemic control and blood lipids, particularly in people with chronic disease. Supplementation with zinc may also improve severe acne, but higher-quality trials are needed to bolster the current evidence.
In the short term, consuming zinc in excess of the recommended upper limit (40 mg/day) can result in gastrointestinal symptoms (e.g., abdominal pain, nausea, vomiting, diarrhea). In the long term, excessive zinc intake has been associated with copper deficiency and iron deficiency, as well as suppression of the immune system. Also, the application of intranasal zinc has been reported to cause a loss of smell in some people.
Adequate dietary intake of zinc is essential for proper growth and development during pregnancy and throughout infancy, childhood, and adulthood. Additionally, zinc is required for normal development, activity, and function of both innate and adaptive immune cells; proper function of pancreatic beta-cells and glucose uptake; and spermatogenesis and normal sperm physiology (e.g., sperm motility).
In the brain, zinc ions inhibit N-methyl-D-aspartate (NMDA) receptors, which is relevant to depression because this condition is characterized by elevated glutamatergic neurotransmission (to which NMDA receptors contribute). Zinc may also benefit depression by increasing brain-derived neurotrophic factor levels.
Zinc supplements vary in their dosages from 5–10 milligrams (mg) up to 25–45 mg, and sometimes higher. Dosages in the lower range are typically used as a daily preventative, whereas dosages in the higher range are typically used to treat chronic conditions and zinc deficiency.
Zinc supplements contain different forms of zinc. Each of these forms contains different amounts of elemental zinc, which refers to the weight of the zinc molecule by itself, for example:
- Zinc acetate is approximately 36% zinc by weight; therefore, 140 mg of zinc acetate contains 50 mg of elemental zinc.
- Zinc picolinate is approximately 21% zinc by weight; therefore, 237 mg of zinc picolinate contains 50 mg of elemental zinc.
- Zinc citrate is approximately 11% zinc by weight; therefore, 439 mg of zinc citrate contains 50 mg of elemental zinc.
- The content of zinc sulfate depends on which form is used. The anhydrous, monohydrate, and heptahydrate forms of zinc sulfate are 41%, 36%, and 23% zinc by weight, respectively; therefore, 123 mg of anhydrous zinc sulfate, 137 mg of zinc sulfate monohydrate, and 220 mg of zinc sulfate heptahydrate each contain 50 mg of elemental zinc.
- Zinc gluconate is approximately 14% zinc by weight; therefore, 348 mg of zinc gluconate contains 50 mg of elemental zinc.
- Zinc monomethionine is approximately 31% zinc by weight; therefore, 163 mg of zinc monomethionine contains 50 mg of elemental zinc.
This can be confusing, but most zinc product labels indicate the elemental weight of zinc that each dose provides. For example, if a label says “Zinc (as picolinate) 50 mg”, this means that each dose provides 50 mg of elemental zinc.