These popular supplements aren’t the cure-all they’re claimed to be

As dietary supplement companies duke it out for precious space in consumers’ minds, social media influencers have emerged as key marketing vehicles. And that’s especially true for the public’s favorite group of supposed miracle substances: antioxidants. But does the science match the hype?

Consider that nearly 1.8 million Instagram posts carry the hashtag #antioxidants, with influencers touting the well-established benefits of fruit and vegetables and the murkier effects of questionable supplements. Entire blogs exist to connect antioxidant supplement producers with digital influencers, promising financial success and a cause that social media marketers can feel good about.

Research on the health benefits of antioxidants abounds—and for good reason. Studies have found that these substances may help with everything from reducing the risks of cardiovascular disease and all-cause mortality to improving skin health.

Some hopeful claims circulating online rely more on optimism than evidence, though, as illustrated earlier this year when several South Korean social media influencers were busted for falsely advertising that several supplements could treat or prevent disease. Furthermore, researchers have found that certain antioxidants might even be harmful to health.

The truth is, antioxidants are no magic bullet, so we have combed through the scientific literature to better understand how antioxidants can help and hurt your health—because the best weapon in the fight against disinformation is quality evidence.

New potential advantages of antioxidants

Let’s start with the basics. Antioxidants are substances that are most often found in plant-based foods. They include vitamins C and E as well as carotenoids like lycopene. Researchers are particularly interested in antioxidants for their potential to shield cells from free radicals— molecules that enter the body when it converts food into energy or is exposed to damaging chemicals.

Several decades ago, studies began linking lower consumption of antioxidants to higher risk of conditions such as atherosclerosis, cancer, and vision loss, according to Harvard public health experts. Since then, many researchers have unearthed promising findings about antioxidants, and their work continues to this day.

During the past several years, investigators have published papers suggesting that various antioxidants may help restore fertility in patients who are exposed to pollution, prevent toxicity in cells under siege by contaminants found in water, and even defend blood vessels from high salt intake. Taken together, studies like these spotlight the diverse benefits of antioxidants. But, they also suggest that the hype can get ahead of the science.

In exploring an antioxidant called Coenzyme Q10 (CoQ10), for example, Harvard Medical School researchers set out to understand how the substance might affect reproductive damage caused by bisphenol A, a common endocrine disruptor. The results, published this year in the journal Genetics, were promising enough to garner headlines. The antioxidant, indeed, reversed some fertility problems—in worms.

“CoQ10 rescued a lot of the defects we’d reported before,” said senior study author Monica Colaiácovo, PhD, professor of genetics, Blavatnik Institute, Harvard Medical School, Boston, MA. “It’s exciting to consider that we could be looking at a simple, low-cost intervention.” She also called for more research in animal and human subjects.

Researchers from Penn State, meanwhile, found cause for applause in a recent research paper in Journal of Nutrition on the effects of a high-cheese, antioxidant diet on blood vessels battling high sodium intake. The randomized crossover design study found that adults who consumed large amounts of sodium did not experience blood vessel dysfunction when they ate four servings of cheese per day, thanks, at least in part, to antioxidants.

“There is scientific evidence that dairy-based nutrients, specifically peptides generated during the digestion of dairy proteins, have beneficial antioxidant properties, meaning they have the ability to scavenge these oxidant molecules and thereby protect against their damaging physiological effects,” said Billie Alba, PhD, lead author and a former researcher at Penn State.

While that study focused on humans, it also set off a media frenzy, even as Dr. Alba and team called for further investigation.

Can antioxidants harm human health?

There is some evidence to suggest that antioxidant supplements can cause harm—or, at the very least, cause disappointment.

When antioxidants began to attract attention, researchers embarked on a number of trials to determine the efficacy of supplements in fighting chronic diseases. As Harvard public health experts note, “the research results were mixed, but most did not find the hoped-for benefits,” adding that “most research teams reported that vitamin E and other antioxidant supplements didn’t protect against heart disease or cancer.”

Indeed, studies of more than 100,000 people have explored how antioxidant supplements might ward off diseases ranging from cancer to cataracts, according to the NIH. “In most instances,” the agency wrote, “antioxidants did not reduce the risks of developing these diseases.”

A 2018 systematic review published in The American Journal of Clinical Nutrition found that while higher consumption of vitamin C and carotenoids were linked to lower risks of cardiovascular disease, total cancer, and all-cause mortality, the findings didn’t apply to antioxidant supplements. The benefits, it turns out, may well have been due to the blend of antioxidants and other good substances found in fruits and vegetables.

Some research has also found potential links between antioxidant supplements and disease.

A study published last year in the Journal of Clinical Oncology, for example, suggested that some antioxidant supplements might increase the risk of disease recurrence in patients with breast cancer. That study joined earlier findings that suggested antioxidants might raise the odds of lung cancer in smokers and boost tumor growth and metastasis in mice. Antioxidants such as vitamin E might also promote the risk of bleeding in patients who take blood thinners, according to the NIH.

What to know about antioxidants

While you’d be hard-pressed to find a study that advises patients to avoid foods that contain antioxidants, there’s a lot of reason to be skeptical of claims surrounding antioxidants. The press—and the dietary supplement market—jump on positive research about antioxidants, but they often turn a blind eye to research that finds antioxidants irrelevant or even dangerous to health. What is clear, however, is that a healthy helping of fruit and vegetables will rarely do you wrong.