Zinc

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.^[1][2]

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.^[3] In some countries, the flours used in cereals are fortified with zinc.^[4]

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.^[5] 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.^[6][7][8] In children, zinc may help prevent pneumonia.^[9][10] However, further high-quality studies are needed to bolster the evidence in this field.

Supplementation with zinc has been shown to improve depressive symptoms^[11][12] and markers of glycemic control and blood lipids, particularly in people with chronic disease.^[13][14][15] Supplementation with zinc may also improve severe acne, but higher-quality trials are needed to bolster the current evidence.^[16][17]

In the short term, consuming zinc in excess of the recommended upper limit (40 mg/day)^[1] can result in gastrointestinal symptoms (e.g., abdominal pain, nausea, vomiting, diarrhea).^[1][18] In the long term, excessive zinc intake has been associated with copper deficiency and iron deficiency, as well as suppression of the immune system.^[19][20][21] Also, the application of intranasal zinc has been reported to cause a loss of smell in some people.^[22]

The potential benefits derived from supplementation with zinc seem to be at least partly attributable to zinc’s anti-inflammatory and antioxidant properties.^{[2][23][24][25]}

Adequate dietary intake of zinc is essential for proper growth and development during pregnancy and throughout infancy, childhood, and adulthood.^[2][26] Additionally, zinc is required for normal development, activity, and function of both innate and adaptive immune cells;^[19][27] proper function of pancreatic beta-cells and glucose uptake;^[28] and spermatogenesis and normal sperm physiology (e.g., sperm motility).^[29]

In the brain, zinc ions inhibit N-methyl-D-aspartate (NMDA) receptors,^[30] which is relevant to depression because this condition is characterized by elevated glutamatergic neurotransmission (to which NMDA receptors contribute).^[31] Zinc may also benefit depression by increasing brain-derived neurotrophic factor levels.^[32][33]