Zinc is an essential dietary mineral that has numerous roles in the body, most notably as a catalytic and structural element in hundreds of metalloproteins. Meat, egg, and legume products are common sources. Oysters are particularly good sources of zinc.
Zinc has two standard dosages. The low dosage is 5-10mg, while the high dosage is 25-45mg. The low dose works well as a daily preventative, while the high dosage should be taken by anyone at risk for a zinc deficiency.
Different forms of zinc contain different amounts of elemental zinc, which refers to the weight of the zinc molecule by itself (Note: Product labels tend to mark the elemental weight)
• Zinc citrate is approximately 34% zinc by weight. For a dose of 50mg elemental zinc, take 146 mg zinc citrate.
• Zinc sulfate is approximately 22% zinc by weight. For a dose of 50mg elemental zinc, take 220 mg zinc sulfate.
• Zinc gluconate is approximately 13% zinc by weight. For a dose of 50mg elemental zinc, take 385 mg zinc gluconate.
• Zinc monomethionine is approximately 21% zinc by weight. For a dose of 50mg elemental zinc, take 238 mg zinc monomethionine.
Zinc should be supplemented daily.
Superloading zinc by taking up to 100mg zinc a day is confirmed to be safe in the short term (2-4 months), but because this dose is higher than the 40mg Tolerable Upper Limit (TUL) of zinc, prolonged superloading is not advised. Zinc’s intestinal uptake is hindered by other minerals, including calcium, magnesium, and iron, since they all use the same transporter. If the transporter’s uptake limit (800mg) is exceeding between these four minerals, absorption rates will fall. Taking less than 800mg of these four minerals at the same time is fine.
Any benefits of zinc supplements or increased dietary intake will depend on the zinc status of the individual. Some research suggests that when zinc levels are low, insulin sensitivity and testosterone can decrease, and supplementation can bring levels closer to normal. Other areas of note are depression and acne, which can frequently benefit from increased zinc intake if levels are low. Zinc is lost through sweat, making supplementation very important for athletes that don’t get a lot of zinc through food. Insulin resistance can also decrease zinc levels.
Zinc deficiency in childhood can impair growth. In adults, zinc deficiency can result in hypogonadism in men, as well as mental lethargy, depression, and skin abnormalities. Low levels of zinc due to diabetes can further worsen insulin resistance. It is estimated that inadequate zinc intake affects around 10% of persons in the US, but global insufficiency rates are over 50%.
Large doses of zinc can produce nausea and other forms of gastrointestinal upset, particularly when taken on an empty stomach. Large doses of zinc can also cause a copper deficiency and lead to overdose. Many supplements use far more than the RDA, and a combination of supplements, fortified foods, and high zinc foods may lead to exceeding the tolerable upper intake level for adults, which is 40 mg per day. High dose zinc lozenges can lead to nausea and a metallic taste in the mouth, and should only be taken for a short time, if at all.