Vitamins and Supplements Can’t Replace a Balanced Diet, Study Says

Roughly 90% of American adults do not eat enough fruits and vegetables, but many are trying to make up for it by popping pills. According to the Council for Responsible Nutrition, 75% of U.S. adults take a dietary supplement of some kind. Multivitamins, many people believe, are a one-step way to get the nutrients they need.

But research published in 2019 in the Annals of Internal Medicine suggests that vitamins and supplements may not be enough to keep you healthy.

Nutrients consumed via supplements do not improve health and longevity as effectively as those consumed through foods, according to the study. While getting the right nutrients in the right quantities from food was associated with a longer life, the same wasn’t true for nutrients from supplements, says study co-author Fang Fang Zhang, an associate professor of epidemiology at the Tufts University Friedman School of Nutrition Science and Policy.

“For the general population, there’s no need to take dietary supplements,” Zhang says. “More and more evidence suggests no benefits, so we should go with what the dietary recommendations suggest to achieve adequate nutrition from food, rather than relying on supplements.”

The researchers used data from about 30,000 U.S. adults who participated in the National Health and Nutrition Examination Survey from 1999 to 2010. Each person provided information about their supplement use in the past month — more than half had used at least one — as well as their dietary habits. Researchers then used that information to determine participants’ nutrient levels.

During the follow-period, which lasted about six years, more than 3,600 people died.

When Zhang and her colleagues first started examining the data, it looked as though dietary supplements were associated with a lower risk of early death, she says. But after they adjusted for factors like education, socioeconomic status and demographics, it became apparent that mostly higher-income, better-educated people — who are more likely to be in good health to begin with — were taking supplements. After that adjustment, the connection between supplements and longevity disappeared.

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Getting enough vitamin A, vitamin K, magnesium, zinc and copper were all associated with a lower risk of dying early, the researchers found — but only when those nutrients came from food.

In fact, some supplements even appeared to come with health risks. People who took high doses of calcium via supplement had a 53% higher risk of dying from cancer than people who were not taking supplements, the study says. But excess calcium from food was not associated with a similar uptick in mortality risk, Zhang says, which suggests that the body may not be able to clear excess supplemental calcium as well as it can natural calcium. The connection between excess calcium and cancer still isn’t totally clear and will require more research, she says.

People who took vitamin D supplements but were not deficient in vitamin D also had a higher risk of dying during the study period, the researchers found, but the supplements did not seem to boost death risk for those who were lacking in vitamin D. Some studies have shown that vitamin D supplements may reduce risk of death and disease, while some have not.

The Annals of Internal Medicine study, however, says there’s not much evidence that supplements of any sort can prolong your life, despite their widespread use. Supplements also are not tightly regulated in the U.S., meaning they can come with safety, efficacy and quality issues. One 2015 study estimated that unsafe or improperly taken supplements, including those for weight loss, send more than 23,000 Americans to the emergency room each year.

The Food and Drug Administration (FDA) does not hold supplements to the same standards as conventional foods or drugs, so manufacturers are responsible for handling safety testing and labeling themselves; the FDA only steps in when there’s an issue with a product already being sold.

Zhang says a few populations may benefit from certain supplements, including the elderly — who often struggle to absorb nutrients from food — and those with dietary restrictions that may lead to deficiencies. But with an abundance of uncertainty and a lack of evidence for supplements, Zhang says the average person should just eat a balanced diet that contains plenty of fruits, vegetables and whole grains, rather than turning to over-the-counter solutions.

“Over half of Americans use these, and the reason is to improve or maintain health,” Zhang says. “That mindset needs to be changed, given the evidence.”