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Over-Supplementing Zinc Can Worsen Your Chances of This Common Infection

Over-Supplementing Zinc

In the fall and winter, many begin taking vitamin and mineral supplements to help boost the immune system to prevent cold and flu. Here is one reason why you may want to rethink that decision.


Zinc is a very important mineral necessary for human health. It is essential for wound healing, for example, and for brain health. Many utilize zinc supplements to treat the common cold in the winter – it is even added to some cough suppressant lozenges. Some research indicates that zinc can shorten the length of colds.

However, as with most nutrients, while some is good, too much may indeed be harmful.

Recent research suggests that too much dietary zinc can increase the changes of an infection known as Clostridium difficile, or C. Diff. C. Diff infection affects about a half a million people each year in the US, causing symptoms ranging from diarrhea to life-threatening inflammation of the colon. Per Dr. Eric Skaar PhD MPH, professor of Pathology, Microbiology, and Immunology at Vanderbilt University, the rates of C. Diff have been recently increasing.

A team of scientists have found that high levels of zinc can change the gut’s microbiome – which is the community of organisms that lives in our gastrointestinal tract – in a way that mimics antibiotic treatment. This is the primary risk factor for developing C. Diff as it makes one more susceptible to an increase in “bad” bacteria in the gut.

"Everyone's microbiome is unique, and each microbiome is differentially affected by environmental factors, such as diet," Skaar said. "It is important to know what you are putting into your body. Multivitamins and other supplements are really only needed by those with a particular nutritional deficit in their diet."

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Keep in mind that zinc is a “micronutrient”, meaning your body doesn't need a large amount. The recommended daily allowance for adults is 8 - 11 mg.

The best food sources of zinc include shellfish (especially oysters, shrimp and crab), red meats, poultry, and cheese (ricotta, swiss and gouda). Other good sources include legumes (lima beans, black eyed peas, pinto beans, soybeans, and peanuts), whole grains, miso, tofu, brewer’s yeast, cooked greens, mushrooms, green beans, tahini, and seeds (pumpkin and sunflower).

If you are overall eating a healthy, varied diet, you are likely to be getting all the zinc your body needs. If you feel you fall short, take a general multivitamin and you should be covered!

Journal Reference:
Joseph P Zackular, Eric P Skaar et al. Dietary zinc alters the microbiota and decreases resistance to Clostridium difficile infection. Nature Medicine, 2016; DOI:10.1038/nm.4174

Additional Resource:
University of Maryland Medical Center

Photo Credit:
By U.S. Army Corps of Engineers Norfolk District from United States via Wikimedia Commons