Zinc is a mineral that's involved in more than 200 different chemical reactions in the human body. It's involved in the metabolism of protein, bone mineralization, alcohol metabolism, wound healing, healthy immune function and fertility, to name a few. Fortunately, zinc is available from a variety of food sources, although animal-based foods are better sources than plant-based ones. Some of the best sources of dietary zinc include seafood, beef, liver, lamb, pork, dark-meat turkey, chicken, wheat germ, wheat bran, pecans, sunflower seeds and chickpeas. Some breakfast cereals and other foods are fortified with zinc. Zinc from animal sources is better absorbed than zinc from plant sources.
It was once thought that zinc deficiency was uncommon, but more recent research suggests that a significant number of people may not get enough zinc in their diet. This includes vegetarians, alcoholics and people who eat a calorie-restricted diet. Some digestive problems such as inflammatory bowel disease and celiac disease reduce zinc absorption and increase the risk of deficiency. Taking large quantities of minerals such as magnesium, iron and copper can also interfere with the absorption of zinc.
Zinc deficiency can have serious consequences. Adults who are deficient in zinc may experience loss of the ability to taste and smell, low sex drive, infertility, poor wound healing, hair loss, skin problems and an increased risk of infection. Children with low zinc levels can have delayed growth and sexual development.
Some research suggests that zinc can shorten the duration of a cold by several days. That's why some people with the sniffles pop zinc lozenges at the first sign of a cold to shorten its course. This may be effective for some, but there are potential side effects. Some people experience nausea and an unpleasant taste in their mouth after using oral zinc or zinc lozenges. One of the more serious side effects is loss of the ability to smell, but this is only a risk for forms of zinc applied directly to the nose.
Not only is zinc important for wound healing, it's beneficial for the treatment of acne. Research suggests that oral zinc gluconate in supplement form reduces the number of inflammatory acne lesions. Zinc may also be beneficial topically for treating inflammatory acne. According to a study published in the European Journal of Dermatology, a combination of topical erythromycin and zinc acetate was effective for reducing the number of active acne lesions and comedones.
Another form of zinc called zinc pyrithione is effective for treating dandruff. That's why it's an ingredient in some dandruff treatment shampoos. It also appears to modestly boost hair growth in men with androgenic alopecia.
Zinc in the form of zinc oxide is used as an active ingredient in physical sunscreens that work by blocking or deflecting the sun's rays so they don't cause skin damage. Some people prefer physical sunscreens over chemical ones since they stay on the surface of the skin and aren't absorbed. Zinc oxide is a highly effective ingredient in such products.
Recently, scientists in Japan discovered that a zinc salt called zinc PCA helps to protect skin against damage caused by ultraviolet light from the sun. It does this by suppressing an enzyme activated by ultraviolet light that breaks down collagen. It also appears to boost collagen production in the dermis of the skin. This is important since collagen levels decline with age, and collagen is important for keeping skin firm and wrinkle-free. Zinc PCA is already used in some cosmetic products as an astringent and a preservative.
Is topical and supplemental zinc safe? Taking high doses of zinc orally can interfere with absorption of other minerals, particularly copper. It's possible to develop a copper deficiency from taking large amounts of zinc. This is something to consider before taking zinc in supplement form, although there's a little risk of this when taking the amounts used in acne treatment. Zinc supplements can also cause nausea and diarrhea. Topical zinc in cosmetic and skin care products including sunscreens appears to be safe.