By Barbara Broggelwirth, RDN, CDN

Are you supplementing with zinc? Be careful! Excess zinc intake can lead to a copper deficiency which can cause neurological problems, including numbness and weakness in the arms and legs.  Zinc is a trace mineral, meaning that we only need small amounts of it to support our health. It is found in cells throughout the body and supports the immune system to fight off pathogenic bacteria and viruses. The body also uses zinc to make proteins and DNA, helps wounds heal and is important for proper senses of taste and smell.

How much do we need? That all depends on your age and your dietary intake. There are certain populations that may be at greater risk for zinc deficiency such as people who have had weight loss surgery, people who have digestive disorders such as Crohn’s disease and ulcerative colitis, vegetarians, alcoholics and those with sickle cell disease. Having said that, zinc deficiency is rare in the United States. Symptoms of zinc deficiency include hair loss, diarrhea, eye and skin sores and loss of appetite. But keep in mind that these symptoms can be signs of other problems as well, so it is important not to self-diagnose. Your doctor can determine this with a simple blood test.

Supplemental zinc is often marketed as an “immune booster.”. Brands like Zicam, which offers a zinc lozenge, state that it is “clinically proven to shorten colds at the first sign.” However, according to the National Institute of Health (NIH), while there is some evidence to support this claim, further research needs be done on the dose and duration needed to be effective. Also, the way in which zinc is administered matters. Zinc-containing syrup and lozenges are most effective at fighting colds because they allow the zinc to make contact with the rhinovirus in those areas.

Adverse effects of high zinc intake include nausea, vomiting, loss of appetite, abdominal cramps, diarrhea, and headaches. Intakes of 150–450 mg of zinc per day have been associated with such chronic effects as low copper status, altered iron function and reduced immune function. Zinc can also interact with certain medications such as antibiotics, diuretics, and penicillamine (a drug used to treat rheumatoid arthritis).

So now that we’ve unpacked the efficacy of supplemental zinc, you may be asking yourself “should I supplement?” Unless a blood test reveals that you are deficient, it is always best to get our vitamins and minerals from food sources. Supplements are not regulated by the FDA so you may be at risk of consuming other harmful ingredients such as lead or other contaminants, and the amount listed on the label might not be reflective of how much is in it; it could be much more or much less. Additionally, vitamins and minerals work synergistically with one another when obtained from their natural food sources. The federal government’s 2015-2020 Dietary Guidelines for Americans advises, “Nutritional needs should be met primarily from foods… Foods in nutrient-dense forms contain essential vitamins and minerals and also dietary fiber and other naturally occurring substances that may have positive health effects.”

Food sources of zinc include:

  • Red meat and poultry
  • Beans
  • Nuts
  • Crab, lobster and oysters (Fun fact! Oysters contain more zinc per serving than any other food – 673% of daily value)
  • Whole grains
  • Fortified breakfast cereals
  • Dairy products

Guidelines for supplementing with Zinc: 

  • Do not supplement with zinc capsules / tablets unless your doctor tells you that your blood levels are low. Don’t just assume you are deficient.
  • A lozenge or syrup taken at the onset of a cold at the recommended dose for a week or two is safe.
  • Steer clear of zinc supplements that exceed the tolerable upper limit (see table below).

The Tolerable Upper Intake Level (Us) is defined as the highest level of daily intake that is likely to pose no adverse health effects in most human individuals. See below for a table outlining the Uls for zinc.

Chart of Zinc Intake Levels

Source: National Institute of Health