Can Supplements Actually Boost Your Immune System?

New York Times

24-02-2025

While perusing the supplement aisle, you'll likely pass bottles of pills and gummies claiming to boost your immune system.
And if you've ever felt tempted to try them, you're far from alone: Recent research suggests that millions of Americans have used dietary supplements for those supposed benefits.
The new study was published last week in JAMA Network Open and included more than 15,000 participants. It found that about one in nine U.S. residents used supplements to enhance their immune systems between January 2017 and March 2020.
'It comes up all the time,' said Dr. Michael Ben-Aderet, the associate medical director of hospital epidemiology at Cedars-Sinai in Los Angeles who wasn't involved with the study. 'There's really this sense of people trying to optimize their health.'
Many people also used the supplements without a doctor's recommendation, the researchers found. But infectious disease doctors, researchers, and supplement experts say there isn't much evidence that these products actually help.
What does the science say?
Supplements claiming to support immunity often contain vitamins and minerals necessary for the immune system. So it isn't unreasonable to believe that these products could help you sidestep common viral infections or lessen symptoms once you've become sick.
In fact, some nutrients such as vitamins A, C, D and zinc are needed to protect against germs, and deficiencies in them raise your risk of becoming sick, said Dr. Mahtab Jafari, a professor of pharmaceutical sciences at the University of California, Irvine.
However, most people in the United States get the vitamins and minerals they need through a balanced diet, said Dr. Ben-Aderet. For those people, there isn't compelling evidence that supplements are useful, he added.
There are thousands of supplements claiming to help the immune system. Some contain just one vitamin or mineral, and others are packed with a hodgepodge of ingredients. Vitamin D, vitamin C and zinc are among the most studied and prevalent ingredients, experts said, and the benefits still aren't conclusive.
Research suggesting that vitamin D supplements treat viral infections like the common cold or reduce the risk of them is inconsistent. A 2020 review found that the supplements didn't protect against viruses in people with normal or high levels of vitamin D. A 2021 review involving nearly 50,000 participants, however, found that vitamin D supplements slightly reduced the risk of acute respiratory infections. (But the review involved authors who have received funding from supplement companies.)
The evidence is similarly unconvincing for vitamin C and zinc. A 2013 review from the Cochrane Library involving more than 11,000 participants found that vitamin C supplements failed to reduce the risk of catching a cold in the general population, though it sometimes shortened how long the illness lasted. And a 2024 Cochrane review involving more than 8,000 participants found that zinc supplements did next to nothing to prevent the common cold, though it may have reduced duration.
Plants like elderberry and echinacea are also used in immune system supplements. But unlike vitamins and minerals, botanicals aren't essential for immune health, and there's even less reliable research on whether they help prevent or treat common viruses, said Dr. Jen Wall Forrester, senior medical director of infection prevention at UC Health in Cincinnati.
'I wish there was a magic bullet,' she said, but immunity is complex, and supplements are unlikely to single-handedly change how it works.
Why don't we know if they help?
It's hard to firmly state the benefits of immune system supplements because there are few high-quality randomized clinical trials, the gold standard of medical research, assessing their effectiveness, said Dr. Pieter Cohen, an associate professor at Harvard Medical School who studies dietary supplement safety.
And dietary supplements aren't approved by the Food and Drug Administration before hitting the market. This means companies can sell products containing ingredients that haven't been rigorously tested to offer benefits, Dr. Cohen said, and they generally don't have to prove to the F.D.A. that their products contain what they claim.
A 2022 study analyzing 30 supplements marketed to support the immune system found that more than half had inaccurate labels, 13 were misbranded and nine contained ingredients not listed on the label.
What's the bottom line?
'You need to have a really healthy dose of skepticism when you're pulling something off the shelf,' Dr. Ben-Aderet said.
But if you want to give supplements a try, check for high-quality third-party seals of approval from organizations such as U.S. Pharmacopeia or NSF, which test the quality of dietary supplements, Dr. Jafari said. Also scan the F.D.A.'s website to see if the agency has ever issued a warning letter to the supplement company for misleading claims or poor manufacturing, she added.
And talk to a health care provider before taking supplements. They can test your blood for deficiencies, inform you of side effects and unsafe dosages, and let you know whether some supplements could dangerously interact with medications you take, Dr. Wall Forrester said.
If your doctor says the supplement you want to try is generally safe, you 'could just try it out,' Dr. Wall Forrester said, 'but you might be wasting your money.'