No, zinc supplements are not proven to prevent or treat colds

With cold and flu season in full swing, many people are searching for home remedies to fend off viruses or to treat symptoms like a stuffy nose, cough and sore throat.

Many people online recommend taking zinc supplements to fight off colds, claiming they can prevent illness, shorten the duration of a cold or reduce the severity of your symptoms.

Claims like these have led multiple readers, including Sandra, to ask whether zinc supplements really provide these benefits. 

VERIFY dug into the existing research to find out if zinc is scientifically proven to prevent or treat colds. 

THE QUESTION

Are zinc supplements scientifically proven to prevent or treat colds?

THE SOURCES

• The National Institutes of Health (NIH)
• The Mayo Clinic
• Mount Sinai Health Systems
• The U.S. Food and Drug Administration (FDA)
• Nebraska Medicine
• Payal Kohli, M.D., an internist and cardiologist who teaches at Duke and Johns Hopkins Universities
• Cochrane, an international nonprofit organization that synthesizes medical research findings
• Meta-analysis of multiple scientific trials on zinc and the common cold published in 2017
• Study on zinc and the common cold published on BMJ Open in 2020
• Cochrane review of studies on zinc and the common cold published in May 2024

THE ANSWER

No, zinc supplements are not scientifically proven to prevent or treat colds. 

WHAT WE FOUND

Zinc supplements are not scientifically proven to prevent or treat colds, as some social media posts appear to imply.

Some studies suggest zinc supplements may help you feel better more quickly, but the evidence remains inconclusive. Taking zinc in high doses and for an extended period of time can also lead to health complications, medical professionals say.

“The evidence on zinc is far from settled: we need more research before we can be confident in its effects,” Susan Wieland, an assistant professor at the University of Maryland School of Medicine who authored a 2024 review of existing studies on zinc supplements and the common cold, said.

Payal Kohli, M.D., an internist and cardiologist who teaches at Duke and Johns Hopkins Universities, shared a similar sentiment. 

“Most scientists and physicians at this point aren’t really thinking that zinc supplementation either will help to prevent colds or help to substantially shorten their duration,” Kohli told VERIFY. 

She added that people should be “careful about supplementing something that doesn’t have proven benefit” and could potentially have harmful effects. 

Studies show mixed results on zinc for cold prevention, treatment

The U.S. Food and Drug Administration (FDA) does not approve any dietary supplements, including zinc, for safety or effectiveness before they are sold to the public. 

But many researchers have conducted studies over the years on the potential benefits of zinc supplements in preventing and treating the common cold. Those studies have had mixed results, Kohli told VERIFY. 

One meta-analysis of multiple scientific trials published in 2017 concluded that 80 to 92 mg per day of zinc taken early in the course of a common cold would reduce its duration by about 33%. In other words, a person would feel better more quickly.

But another study published on BMJ Open in 2020 found no difference in recovery rates between people who took about 80 mg of zinc per day versus a placebo when they caught a cold. 

In a Cochrane review published in May 2024, a team of researchers analyzed 34 studies on zinc for the prevention and treatment of the common cold – 15 for prevention and 19 for treatment. The majority of the studies were conducted on adults. 

The studies varied in how zinc was administered, how much zinc people received, how a cold was defined and what they measured.

Eight studies with 972 total participants looked at zinc as a treatment to reduce the length of a cold. The combined results of these studies “yielded low-certainty evidence that it may help reduce duration by around two days, down from an average week-long duration in the groups who received placebo,” Cochrane said. 

However, their review found “no strong evidence” that zinc “impacts the severity of cold symptoms.” 

In other words, a person may recover more quickly, but zinc won’t make their symptoms less severe, the review found. 

The studies that looked at prevention also showed “no clear evidence” that taking zinc before the onset of a cold benefits people, according to Cochrane.

“While there have been many trials investigating zinc, the approaches vary, so it is difficult to draw conclusions with certainty,” Daryl Nault, an author of the Cochrane review and assistant professor at the Maryland University of Integrative Health, said. 

Wieland said future studies on zinc supplements and treating the common cold should “adopt standardized methods for administering and reporting treatments and defining and reporting outcomes.”

Too much zinc can lead to adverse health effects

Zinc is a nutrient found in the body that helps your metabolism and immune system function.

People who eat a balanced diet usually get enough zinc, since common foods like chicken, red meat and fortified breakfast cereals are sources of the nutrient, the Mayo Clinic says. 

Your body doesn’t need a large amount of zinc, Mount Sinai Health Systems says. The recommended daily allowance of zinc for adults is 11 mg for men and 8 mg for women, with 40 mg a day being the upper limit dose, according to the National Institutes of Health (NIH). 

Zinc is also available as a dietary supplement in various forms, including lozenges, pills, liquids, powders and nasal sprays. Some of the oral zinc supplements VERIFY found online contained more than half of the tolerable upper limit dose of 40 mg a day.

These supplements can lead to some unpleasant side effects and even serious health complications if a person takes too much.

If zinc is taken in large amounts, it can cause diarrhea, abdominal cramps and vomiting, according to the NIH.

According to the Mayo Clinic, when oral zinc is taken in the long term over an extended period of time, it can also lead to copper deficiency. People with low copper levels can experience neurological issues, such as numbness and weakness in their arms and legs, the Mayo Clinic says. 

Mount Sinai says people should not take high doses of zinc for more than a few days unless a doctor tells them to do so. The health system recommends talking to a doctor before taking more than 40 mg of zinc per day and taking breaks from zinc supplements. 

Zinc can also interfere with certain medications, such as antibiotics, rheumatoid arthritis drugs and certain blood pressure drugs, Nebraska Medicine says. People who take these medications should always consult with a doctor before starting a zinc supplement.

The Mayo Clinic also cautions against using zinc nasal sprays, as intranasal zinc has been linked to a loss of smell.