After iron, zinc is the most concentrated mineral in the body. It’s critical for keeping the immune system in good working order and taste and smell sharp. Zinc also helps cells grow and divide and may aid in wound healing.

Few people know how much zinc they need each day, much less how best to get it. But here's the real problem: While too little zinc can cause problems, too much zinc can wreak havoc. And if you're taking zinc supplements, you may be taking too much.

Related: Are Your Nails Trying to Tell You Something?

When supplements backfire

Some people are indeed deficient in zinc, though a deficiency can be hard to spot, according to the Mayo Clinic. The symptoms (thinning hair, weight loss, decreased appetite, and a diminished sense of taste and smell, plus an increased risk for kidney stones) aren’t always pronounced and could be mistaken for other health issues. 

Trying to compensate for low levels of zinc — or attempting to fight a cold — by taking supplements can backfire, however. A study published in the Journal of Clinical Pathology found that getting too much zinc from supplements can affect the body’s ability to absorb copper, which in turn can lead to anemia, a low white cell count and/or neurological problems.

“This is an excellent example of how the overconsumption of one nutrient can compromise the benefits of another,” says Joan Salge Blake, MS, RDN, a registered dietitian and spokesperson for the Academy of Nutrition and Dietetics (AND).

An excess of zinc also can cause stomach pain, nausea, vomiting and diarrhea. Ironically, though some people take zinc to fight colds, too much of this mineral also has been shown to suppress the immune system, as well as lower HDL ("good" cholesterol) in the blood, Salge Blake adds.

Related: Farmed Fish: Yay or Nay?

Why it’s so easy to overdo it

The recommended daily intake of zinc for men is 11 milligrams per day, according to Salge Blake. For women it’s 8 milligrams per day. For people 19 and older, the Tolerable Upper Intake Level (UL) for zinc is 40 milligrams — yet many zinc supplements contain more than that. (Sometimes zinc is prescribed in higher doses to help treat an illness or medical condition, such as stomach ulcers or acne.)

Zinc supplements also are prescribed to treat zinc deficiency, of course. In general, though, most Americans are meeting their daily zinc needs. The best sources of zinc are animal products — lean meat, poultry (especially dark meat), seafood (particularly oysters and herring) and milk.

Getting zinc from your diet 

Some people should make it a point to get more zinc from their diet. “Vegetarians and especially vegans may have a fifty percent greater need for this mineral,” explains Salge Blake. The reason? Certain compounds in grains and legumes, which are staples of vegan and vegetarian diets, can bind with zinc and interfere with its absorption in the intestinal tract. But even vegans don’t need to take supplements, says Salge Blake. They can get their zinc from peas, beans, nuts and whole grain products.

If you eat a lot of highly processed grains, you might want to start reading labels for zinc. “Because zinc is in the germ and bran portion of a grain, refined cereals and bread, which are stripped of these components, have as much as eighty percent less zinc than whole grain products,” explains Salge Blake.

Certain metals also can affect zinc absorption. According to the Mayo Clinic, the zinc in foods packaged in uncoated tins may not be absorbed easily. On the other hand, cooking in iron or steel pots and pans that are galvanized — coated with a protective layer of zinc — can enhance the absorption of zinc.

Related: Going Vegan? 7 Things to Know Before You Start

Jennifer Kelly Geddes is a New York City-based writer and editor who specializes in parenting, health and child development. She’s also the mom of two teen girls.