By Aria Bendix -
NBC News
Vitamins and supplements offer little or no benefit in preventing cancer or heart disease, according to a new review of 84 studies.
Based on this conclusion, an independent panel of experts from the US Preventive Services Task Force said Tuesday that it had "insufficient evidence" to recommend or advise against the use of multivitamins or supplements to prevent these health problems.
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The review examined the effects of popular supplements such as beta-carotene, folic acid, calcium, magnesium, selenium and zinc, as well as multivitamins and vitamins A, B, C, D and E.
But the guidance comes with caveats: It doesn't apply to children, the 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 planning to become pregnant.
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However, for the average healthy adult, "there is no reason to start taking dietary supplements more widely," explained Dr. Howard Sesso, associate director of the Division of Preventive Medicine at Brigham and Women's Hospital.
Sesso is not a member of the working group, but two of his studies were included in the review.
"For those taking a particular multivitamin, I don't think this statement needs to necessarily change what they're doing, but it's always important to reassess why they're taking dietary supplements," Sesso said.
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The US Preventive Services Task Force last gave recommendations on vitamins and supplements to prevent 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 still don't see any convincing evidence that vitamins and supplements in general help prevent heart disease and cancer.”
Jia co-authored an editorial published alongside the review on Tuesday, which said buying vitamins and supplements is essentially "wasted money."
People in the United States spent nearly $50 billion on dietary supplements in 2021, according to the authors.
A healthy diet is 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.
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Experts agree that rather than taking vitamins or supplements, the best way to reduce your risk of cancer or heart disease is to eat a balanced diet high in fruits and vegetables and get regular exercise.
Calcium, vitamin D and magnesium pills and vitamin preparations.Fernando Gutierrez-Juárez / DPA/Picture Alliance via Getty Images
"What should be clear from these guidelines is that a healthy diet remains the first line of defense in preventing chronic disease," Sesso recalled.
"Supplements should in no way represent a crutch or a way to make up for a poor diet," he added.
But vitamins and supplements may have some benefits for older adults who have trouble absorbing nutrients through food.
Sesso noted that there is mixed evidence that multivitamins might reduce the risk of cataracts or age-related macular degeneration, or possibly slow cognitive decline.
"We still have a lot of work to do to clarify this and look at other endpoints beyond the ones that are focused on these recommendations, which are cardiovascular disease and cancer," he said.
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Even the link between multivitamins and cancer needs more research, he added, as the review found that multivitamins may be associated with a marginal benefit for cancer outcomes.
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One of Sesso's trials indicated that daily use of multivitamins reduced the overall risk of cancer among male doctors.
But another trial found no evidence that multivitamins reduced cancer risk in men or women.
“If there is any benefit, it is very small,” Jia concluded.
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Dietary supplements can be purchased without a prescription and do not require Food and Drug Administration (FDA) approval.
That's why manufacturers "have much more room to maneuver with what they can say on their labels," according to Sesso.
“There is a widespread perception that all these dietary supplements are benign,” Jia noted, “when we know that they are not regulated to the same level as drugs by the FDA.
So we don't have such a clear picture of their benefit-harm ratio."
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Sesso noted that it's possible that certain formulations may 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 its formulation compared to a typical tablet," he clarified, adding: "We don't have the kind of evidence from clinical trials to support whether they help, harm or do nothing”.
