Vitamins and supplements offer little to no benefit in preventing cancer or heart disease, a new review of 84 studies found.
Based on that conclusion, an independent panel of experts at the U.S. Preventive Services Task Force said on Tuesday that it had “insufficient evidence” to either recommend or discourage the use of multivitamins or supplements to prevent those health outcomes.
The review examined the impacts of popular supplements like beta carotene, folic acid, calcium, magnesium, selenium and zinc, as well as multivitamins and vitamins A, B, C, D and E.
But the guidance came with caveats: It does not apply to children, people who are chronically ill or those with a known nutritional deficiency. The task force also recommended a daily folic acid supplement for people who are pregnant or considering pregnancy.
For the average healthy adult, however, "there’s no reason to start taking dietary supplements more broadly," said Dr. Howard Sesso, associate director of the Division of Preventive Medicine at Brigham and Women’s Hospital. Sesso is not a member of the task force but two of his studies were included in the review.
"For those who are currently taking a multivitamin in particular, I don’t think this statement necessarily ought to change what you’re doing, but it’s always important to reevaluate why you’re taking dietary supplements," Sesso said.
The U.S. Preventive Services Task Force last gave recommendations on vitamins and supplements for preventing heart disease and cancer in 2014.
Dr. Jenny Jia, an instructor of general internal medicine at Northwestern University Feinberg School of Medicine, said that more large-scale studies have come out since 2014, "and we’re still not seeing any convincing proof that vitamins and supplements in general are helping with prevention of heart disease and cancer."
Jia coauthored an editorial published alongside the review on Tuesday, which said buying vitamins and supplements is essentially "wasted money." People in the U.S. spent nearly $50 billion on dietary supplements in 2021, the authors said.
'A healthy diet is still the first line of defense'
The new review found strong evidence that vitamin E in particular did not prevent cancer or heart disease, while beta carotene was associated with an increased risk of lung cancer and death from heart disease. Consequently, the task force advised against taking either supplement to prevent heart disease or cancer, the same recommendation it gave in 2014.
Experts generally agree that instead of taking vitamins or supplements, eating a balanced diet high in fruits and vegetables and exercising regularly are the best ways to lower one's risk of cancer or heart disease.
"What should be patently clear from these guidelines is that a healthy diet is still the first line of defense against chronic disease prevention," Sesso said. "Supplements by no means should be representing any crutch or any way to make up for an insufficient diet."
But vitamins and supplements might have some benefits, he added, for older adults who struggle to absorb nutrients through food. Sesso pointed to mixed evidence that multivitamins could reduce the risk of cataracts or age-related macular degeneration, or possibly delay cognitive decline.
"We still have a lot more work to be done to really tease this out and look at other endpoints beyond what these recommendations focus on, which are cardiovascular disease and cancer," he said.
Even the relationship between multivitamins and cancer needs more research, he added, since the review found that multivitamins may be associated with a marginal benefit for cancer outcomes. One of Sesso’s trials indicated that daily multivitamin use reduced the overall risk of cancer among male physicians. But another trial found no evidence that multivitamins reduced overall cancer risk in men or women.
"If there is any benefit, it's very small," Jia said.
Little FDA oversight for vitamins
Dietary supplements can be purchased over the counter and don’t require approval from the Food and Drug Administration. Because of that, Sesso said, manufacturers "have a lot more wiggle room with what they can say on their labels."
"There’s a general perception that all these dietary supplements are benign," Jia said, "when we know that these supplements are not regulated at the same level of pharmaceutical drugs by the FDA. So we don’t have as good of a sense of their benefit-to-harm ratio."
Sesso said it's possible that certain formulations could have different health effects.
"You don’t get the same breadth of vitamins and minerals in a gummy vitamin, just because of the nature of how they’re formulated compared to a typical tablet," he said, adding, "We don’t really have the type of clinical trial evidence to support whether or not these help, hurt, or do nothing."