Table of Contents
Table of Contents
Originally posted February 2021 / Updated March 2023
Zinc is a critical trace mineral that is found in every cell in the human body. It primarily functions as a component in over 200 enzymes. The enzymes use zinc to build many important compounds and structural components necessary for human bodily function. Zinc functions in more enzymatic reactions than any other mineral.
Most enzymes are composed of a protein along with an essential mineral and possibly a vitamin. An enzyme cannot function properly if it lacks the essential mineral or vitamin. If zinc levels are low, it disrupts virtually every body system due to its central role in so many enzymes. In addition to its role in enzymes, zinc is required for the proper action of many body hormones, including insulin, growth hormone, and sex hormones like testosterone and estrogen.
Adequate zinc levels are essential to good health. The beneficial effects of zinc are extensive. It is especially important to proper immune function, wound healing, brain, and sensory functions, sexual function, and skin health.
Although severe zinc deficiency is rare in developed countries, it is believed that many individuals worldwide, including in the United States, have a marginal zinc deficiency, especially in the infant and elderly populations. Zinc deficiency can be caused by decreased intake and/or increased utilization. Dietary surveys indicate that average zinc intakes range from only 47% to 67% of the recommended dietary allowance (RDA). Determining marginal zinc deficiency is complex,1 but may be reflected by an increased susceptibility to depression, infection, a decreased sense of taste or smell, and a number of minor skin disorders, including acne and poor wound healing. Some other physical findings that often correlate with low zinc status include decreased ability to see at night or with poor lighting, impaired growth and development in children, testicular atrophy, mouth ulcers, a white coating on the tongue, and marked halitosis (bad breath).
Zinc plays a huge role in overall health. Its importance cannot be overstated. The scientific support for zinc supplementation is extremely well supported in the medical literature. There have been over 1,000 double-blind, placebo-controlled studies where zinc supplementation benefits many different challenges and restores health.
Zinc is a very important supplement to support the structure and health of the skin, hair, and nails. Zinc supplementation has been shown to offer considerable benefits in improving these issues. It strengthens nails, is critical for hair growth and texture, and is required for the skin to retain the proper hydration (water) and oil content.
Zinc supplementation is particularly helpful when the skin is stressed by acne as it exerts beneficial effects on both sebum production and hormonal metabolism. Low zinc levels are often found in adolescents and may be a predisposing risk factor for acne. Several double-blind studies showed zinc supplementation to produce similar results to tetracycline (an antibiotic) in superficial acne and superior results in deeper acne.2,3 Although some people in these studies showed dramatic improvement immediately, most usually required 12 weeks of supplementation before achieving good results. So, be patient.
Zinc has also shown benefits in promoting wound healing. This effect is very important in people with diabetes as they are at risk for poor wound healing and subsequent infections. The same is true for people prone to boils and folliculitis.
The importance of zinc to wound healing was clearly demonstrated in a double-blind study in 60 patients with grade 3 diabetic foot ulcers.4 The patients given 50 mg zinc (sulfate) per day showed significant improvements after 12 weeks in ulcer healing as well as improved blood sugar control, total antioxidant capacity in the blood, blood glutathione levels, and decreased markers of inflammation. All of these improvements were the apparent result of restoring adequate zinc levels to the body.
Zinc deficiency produces profound changes in brain chemistry, resulting in depression and impaired mental function in humans. Zinc deficiency is one of the most common nutrient deficiencies in children and the elderly. It has been suggested to be a major factor in the development of poor mental function and memory and low mood in these age groups. Not surprisingly, clinical studies with zinc supplementation have shown some beneficial effects in improving both mood and some aspects of mental function in both children and the elderly.5
Zinc deficiency is also quite common in some regions of the world, e.g., the Middle East. In one study in Iran, dietary intake of zinc (was significantly lower among subjects with mild to severe depression symptoms than those with no or minimal depressive symptoms.6
Another group where zinc deficiency may be an underlying factor in low mood and brain function is people who are overweight or dealing with poor blood sugar control. In one study, 50 overweight subjects were randomly assigned into two groups and received either 30 mg zinc (monomethionine) or placebo daily for 12 weeks. Zinc supplementation produced improved mood scores and a biological marker of new brain cell production compared to the placebo group.7
Zinc's benefits in improving mood may result from improved sleep quality. In a double-blind clinical trial, the 54 intensive care unit (ICU) nurses who took 50 mg of zinc (sulfate) once every three days for one month experienced significant improvements in sleep quality. These improvements corresponded to the increase in zinc levels in the blood.8
Zinc is involved in virtually every aspect of immune function. Zinc has been referred to zinc as the “gatekeeper” of immune function.9 Zinc supplementation has been shown to reverse low immune function, especially the lowered immunity characteristic of aging.10,11 This effect may be due to restoring blood levels of thymulin (a hormone produced by the thymus gland). As people age the level of thymulin and other immune-enhancing thymus hormones are reduced. Reducing these hormones leads to impaired immune function and an increased risk of infection. By restoring the levels of thymulin, zinc supplementation can significantly improve immune function. Another effect of zinc supplementation noted in studies on the elderly is that it improves overall nutritional status. This effect signifies the importance of zinc in properly absorbing and utilizing other nutrients.
Zinc also possesses some direct antiviral activity, including antiviral activity against several viruses that can cause the common cold.12 The use of zinc supplements, particularly as a lozenge, appears valuable during a cold. However, while some studies showed great results, others did not.13 This inconsistency is due to an ineffective lozenge formulation in the negative studies. In order for zinc to be effective, it must be free (ionized) in saliva. Citric acid appears to reduce its effectiveness. Therefore, be sure to use zinc lozenges free of citric acid. It is also important when using zinc-containing lozenges to relieve a sore throat or common cold. Do not eat or drink citrus fruits or juices 1/2 before and after dissolving the lozenge, as the citric acid will negate the effect of zinc.
Zinc is involved in virtually all aspects of insulin metabolism: synthesis, secretion, and utilization. Unfortunately, zinc deficiency is common in patients with diabetes.14 And without sufficient zinc, insulin does not work properly. Zinc supplementation and virtually all other water-soluble vitamins and minerals are essential as people with Diabetes typically excrete too much zinc and other water-soluble nutrients in the urine. Several studies have shown zinc supplementation improves insulin sensitivity in people with prediabetes or diabetes.15 As discussed above, zinc is also important for proper wound healing and immune function, which is critical in diabetes.
Zinc is critical for male sexual function. It is involved in hormone metabolism, sperm formation, and sperm motility. Zinc deficiency is characterized by, among many other things, decreased testosterone levels and sperm counts. Zinc levels are typically much lower in infertile men with low sperm counts, indicating that a low zinc status may contribute to infertility. Several double-blind studies have shown that zinc supplementation can improve sperm counts and motility. It is especially effective in boosting sperm counts in men with low testosterone levels.16
Zinc has been shown to be beneficial in reducing vision loss in treating age-related macular degeneration (ARMD). Zinc plays an essential role in the metabolism of the retina, and the elderly are at high risk for zinc deficiency.17 In addition to the studies with a combination of nutrients, zinc alone has been shown to improve ARMD. The impressive results of zinc supplementation led to the famous Age-Related Eye Disease Studies conducted by the National Institutes of Health (NIH).
Low zinc levels are linked to premature births, low birth weight, growth retardation, and pre-eclampsia - a serious condition of pregnancy associated with elevations in blood pressure, fluid retention, and loss of protein in the urine. Some studies of zinc supplementation in pregnancy have shown that the zinc-supplemented group demonstrated greater body weight and head circumference than the placebo group and fewer pregnancy complications.18
Premenstrual syndrome is a common occurrence for many women during their reproductive years. Nutritional factors appear to be an underlying factor. For many women, zinc may be the key nutrient to bring things into balance, as several clinical studies have shown positive benefits. For example, in a double-blind trial of 60 young university women, those given 30 mg/day of zinc experienced significant improvements in quality of life scores, especially as it related to both physical (energy levels, sleep quality, reduced breast tenderness, etc.) and psychological aspects (e.g., mood scores) in quality of life assessments in young women with premenstrual syndrome.19,20
Zinc has antioxidant effects and functions in the antioxidant enzyme superoxide dismutase (copper-zinc SOD). Zinc levels are typically reduced in patients with rheumatoid arthritis and other inflammatory conditions. Several studies have used zinc supplementation to restore adequate zinc levels in rheumatoid arthritis, with some of the studies demonstrating corresponding improvements in zinc-related functions.21 Most of the studies utilized zinc in the form of zinc sulfate. Better results may have been produced by using a more absorbable form of zinc.
There are many forms of zinc to choose from. While many clinical studies have utilized zinc sulfate, this form is not as well absorbed as other forms, such as zinc picolinate, acetate, citrate, bisglycinate, oxide, or monomethionine are all excellent forms of zinc. There is data to support each of these forms as being very well-absorbed and able to produce benefits. Most zinc lozenges are made with zinc gluconate, an effective form for this application.
In adults, the dosage range for zinc supplementation for general health support and during pregnancy or lactation is 15 to 20 mg. For children, the dosage range is 5 to 10 mg. When zinc supplementation is used to address specific health concerns, the dosage range for men is 30 to 45 mg; for women 20 to 30 mg. There is no need to go beyond this dosage level.
During the common cold, use lozenges that supply 15 to 25 mg of elemental zinc and dissolve them in the mouth every two waking hours after an initial double dose. Continue for up to seven days. Because high doses of zinc can impair immune function, avoid a daily intake of greater than 150 mg of zinc for longer than one week.
If taken on an empty stomach (particularly if taking zinc sulfate), zinc supplementation can result in gastrointestinal upset and nausea. Prolonged intake at levels greater than 150 mg daily may lead to anemia, reduced HDL-cholesterol levels, and decreased immune function.
Zinc may decrease the absorption of tetracycline and ciprofloxacin. Take any zinc supplement at least 2 hours before or after these antibiotics.
The following drugs increase the loss of zinc from the body or interfere with absorption: aspirin; AZT (azidothymidine); captopril; enalapril; estrogens (oral contraceptives and Premarin®); penicillamine; and the thiazide class of diuretics. Supplementation may be required to maintain zinc status in people taking these drugs.
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