Dietary supplements — vitamins, minerals, botanicals and probiotics — are more popular than ever. More than three-quarters of Americans take at least one, according to the Food and Drug Administration.
Are any of them worth it? The research is mixed. Some vitamins, including multivitamins, have been shown to be beneficial in large, randomized clinical trials. Others have been shown to potentially cause harm. Many lie somewhere in between.
As many as 100,000 different supplement products are sold in stores and online in the U.S., the FDA estimates. They range from multivitamins to herbs to concoctions that promise weight loss, including some that may be toxic or falsely claim to improve brain function.
Robert F. Kennedy Jr., President-elect Donald Trump’s pick for health secretary, told podcaster Lex Fridman in 2023 that he takes “a ton of vitamins and nutrients,” which he said he couldn’t list because he “couldn’t remember them all.” In an October post on X, Kennedy accused the FDA of “aggressive suppression” of vitamins and nutraceuticals, among other things.
In fact, the FDA has limited oversight over supplements after they’re on the market. In a published study from 2018, researchers with the California Department of Public Health raised concerns about products that contain unapproved and potentially unsafe ingredients.
The Dietary Supplement Health and Education Act of 1994 put dietary supplements in the same category as food under the FDA. This framework means the agency regulates dietary supplements as food products rather than pharmaceuticals. As a result, overseeing the products’ safety and efficacy is largely left up to the companies that sell them.
“The FDA does not approve dietary supplements or their product labeling before they are sold to the public,” Dr. Cara Welch, director of the FDA’s Office of Dietary Supplement Programs in the Center for Food Safety and Applied Nutrition, said in an interview on the agency’s website. “In fact, most products can be lawfully brought to the market without FDA even knowing.”
If a company wants to sell a dietary supplement that contains an ingredient that is not already present in food sold in the U.S., the company must submit a “new dietary ingredient” notification to the FDA including a “history of use or other evidence of safety establishing that the dietary ingredient, when used under the conditions recommended or suggested in the labeling of the dietary supplement, will reasonably be expected to be safe.”
The FDA reviews the notifications for safety issues but does not approve or reject the supplement based on the efficacy of the ingredient.
“Only a tiny fraction of the dietary supplements on the market have been rigorously tested for efficacy or safety,” said Dr. JoAnn Manson, chief of the division of preventive medicine at Brigham and Women’s Hospital.
Companies can also use a loophole called generally recognized as safe, or GRAS. This designation allows substances deemed as safe according either to research or the fact that they are already used in food to be used in new products. No notification to the FDA is required.
“Companies can just declare something as GRAS and then add it to supplements, and the FDA will never know about it unless there is a major problem,” said Jensen Jose, regulatory counsel at the Center for Science in the Public Interest, a nonprofit consumer advocacy group.
Limits to the research
Many of the vitamins and minerals on the market are generally safe, if not always effective, and the agency does have the authority to request a recall if a product causes adverse side effects once consumers start using it or if the company is caught making misleading claims about a supplement. Some companies also voluntarily self-regulate.
“What we do in self-regulation is above and beyond what is required in federal regulation,” said Steve Mister, president and CEO of the Council for Responsible Nutrition, a trade association and lobbying group that represents businesses that manufacture supplements. “There is a collective mindset that the industry needs to behave in responsible ways.”
When it comes to research, understanding the effects supplements have on human health is difficult, time-consuming and costly, said Dr. David Seres, director of medical nutrition at the Columbia University Medical Center’s Institute of Human Nutrition.
“The majority of the research that one hears about is observational, where two things are correlated but the cause and effect relationship cannot be established based on that research,” Seres said. “The majority of nutrition research tends to be these kinds of studies.”
“There are clearly supplements with established benefits,” said Christopher Gardner, a professor of nutrition at Stanford University. “There are also many supplements that are likely not beneficial, but also not harmful.”
More doesn’t mean better
Manson, who led the COSMOS-Mind clinical trial on multivitamins, said people should be cautious about vitamins that contain “mega doses.”
“You have to look at the level and see what it says in terms of percentage of daily intake. Often it will say 400% or 500%, well above the daily intake value,” she said.
Such high doses can be dangerous or a waste of money.
The U.S. Preventive Services Task Force, an independent panel of medical experts who make care recommendations regarding preventive and primary care, just drafted a new recommendation that advises against taking vitamin D to prevent falls and fractures among older people, based on evidence that shows it isn’t beneficial — unless someone has a diagnosed deficiency.
There is some evidence that a daily multivitamin can protect against memory loss; however, numerous studies have failed to show that supplements have any miraculous effects on health. A diet like the Mediterranean diet, which is full of plants, vegetables and fatty fish, can lower risks of dementia or heart disease, but supplements usually don’t offer the same benefits, research has found.
“In general, we should be able to get all the nutrients we need from foods, but the reality is many people do not always have access to a reasonable variety of healthy foods,” Gardner said, adding that people who do not have access to a variety of nutritious foods may benefit from some supplements.
For everyone else, more doesn’t mean better.
“Most Americans meet all of their vitamin, mineral and nutritional needs. If intake is already adequate, it is rare when more would help,” he added.
There isn’t one answer for why people take supplements that may be providing little to no benefit, but it may be due to a strong desire to control their health, said Seres.
“The hint of a benefit is a strong temptation when it is assumed that it can’t possibly be harmful and the airwaves are filled with ‘supports XYZ health,’” he said.
