Consumer Reports has no financial relationship with advertisers on this site.
Although many of us are getting fewer colds this year than usual (thanks to all our COVID-19 precautions), we’re also more concerned than ever with keeping our immune systems strong. For some, that means reaching for supplements thought to boost your body’s defenses, and zinc is one of the more popular choices. According to estimates from Nutrition Business Journal, consumers spent $162 million on zinc supplements in 2020, a 35 percent increase over the previous year.
Zinc has a reputation for ending colds more quickly and helping you feel better faster. But as with many supplements, the science surrounding the claims still hasn’t quite caught up to consumer interest.
“We know that people take it a lot, but we also know there isn’t a lot of scientific validation for zinc supplementation,” says Suma Thomas, MD, a cardiologist at the Cleveland Clinic who has studied the possible effects of zinc supplements on COVID-19 patients.
Zinc supplements (like other nutritional supplements) aren’t regulated by the Food and Drug Administration in the same way that medications are. So before you decide to spend your money on zinc pills or lozenges, keep these five points in mind.
Zinc Supplements Won’t Prevent Most Illnesses
“Our bodies need zinc for many things, including proper immune system function,” says Carol Haggans, RD, scientific and health communications consultant at the National Institutes of Health Office of Dietary Supplements. Not getting enough zinc may impair formation of disease-fighting lymphocytes (a type of white blood cell in the immune system). “That’s why people with zinc deficiency might have a higher risk of viral infections,” Haggans says. For those who are severely deficient (only about 15 percent of U.S. adults are at risk), it’s possible that taking extra zinc may reduce the risk of infections, including colds. But for otherwise healthy adults, there’s currently no evidence showing that supplemental zinc will keep you from catching a cold. “The studies out there mostly looked at zinc’s effect on cold symptoms and duration, not prevention,” Thomas says.
Zinc May Help Shorten a Cold but Won't Help With Symptoms (or With COVID-19)
There is some evidence that sucking on zinc lozenges within 24 hours of first feeling cold symptoms may shorten its duration by a day or two, but there’s little to indicate that it eases cold symptoms, such as congestion, cough, or muscle aches.
A 2017 analysis published in Open Forum Infectious Diseases of three previous studies found that people who took 80 to 92 mg per day of zinc (in the form of lozenges) got better faster. By the fifth day, 70 percent of those taking zinc had recovered, compared with just 27 percent of those given a placebo.
A 2020 analysis published in The American Journal of Tropical Medicine and Hygiene reported similar reductions in duration but found conflicting evidence on whether zinc supplements had an effect on the severity of cold symptoms. In other words, you may be stuffed up and sniffling for fewer days, but on the days you’re sick you’re likely to feel just as lousy.
Thomas and her colleagues were intrigued by some of the research on zinc and colds and wanted to see whether zinc supplementation had any beneficial effects on people with COVID-19 (which, like some colds, is caused by a coronavirus). Their study, recently published online in JAMA Network Open, included 214 COVID-positive people with an average age of 45. The researchers divided the participants into four groups. One group received standard treatment, one got high doses of vitamin C, one got high doses of zinc, and the fourth group got both supplements. “We studied doses above the recommended intake [for zinc, it was 50 mg per day, about five times the amount healthy people should get in their diets each day] because that’s what had been shown to be beneficial in previous studies of colds,” Thomas says. “But even at such high doses, we did not find any difference between our four treatment groups in terms of duration or severity of COVID symptoms.”
Taking Zinc Can Make You Feel Sick
Don’t go popping zinc supplements every day thinking you're reinforcing your immune system. The amount of zinc you need daily is 11 mg for men and 8 mg for women. And the Institute of Medicine has set the tolerable upper intake level (the maximum you should consume per day) at 40 mg for adults. Studies looking at zinc’s potential to help shorten or reduce the intensity of colds or other respiratory illnesses have involved daily doses of up to 100 mg, but just for the duration of the illness. If you’re taking zinc on an ongoing basis, “going over the upper limit can cause health problems, including nausea, vomiting, stomach cramps, diarrhea, and low copper levels,” Haggans says. Zinc supplements and lozenges can also leave a metallic taste in your mouth, Thomas says.
Nasal sprays containing zinc were popular cold remedies until the FDA warned that using them could cause you to lose your sense of smell. As a result, most (if not all) nasal sprays have either been reformulated without zinc or taken off the market. There’s no evidence that zinc pills or lozenges cause this side effect, though.
Zinc May Interact With Medications
If you’re planning to take zinc supplements—even just for the duration of a cold—you should talk to your doctor about whether zinc will interact with any other medications you’re taking. For example, taking zinc with certain antibiotics (such as quinolone or tetracycline) can lower both the amount of the medication and the amount of zinc your body absorbs. Zinc supplements can also interfere with the effectiveness of certain rheumatoid arthritis drugs.
You Probably Get all the Zinc You Need in Your Diet
It’s not difficult for most Americans to meet their zinc needs with food alone, and zinc deficiency severe enough to impair immune function is rare in the U.S. Red meat, poultry, and certain types of seafood (like crab, lobster, and oysters) are the best sources of zinc. A 3-ounce burger provides about half your daily need.
Zinc is also found in plant foods, such as seeds, nuts, and legumes, but in lower amounts. An ounce of almonds, for example, contains just under 1 mg. “Vegetarians and vegans, as well as older adults, might be more likely than others to be zinc deficient,” Haggans says. If you’re concerned you might not get enough zinc in your diet, talk to your doctor about whether a zinc supplement or multivitamin with zinc will help keep your immune system healthy.