If you're popping dietary supplements in the hope of living longer, a large new study suggests you'd be better off investing that money in nutritious foods.
The research found that vitamins A and K, magnesium, zinc and copper were linked to a lower risk of death from heart disease or stroke, and an overall lower risk of dying during the average six years of follow-up. But these findings were true only when the nutrients came from foods, not from supplements.
No benefit for general population
Of more concern, the study found that taking at least 1 000 milligrams of calcium daily from supplements was associated with an increased risk of death. This was not true of calcium from food.
"Over half of the United States population takes supplements on a regular basis. But it's pretty clear that supplement use has no benefit for the general population. Supplements are not a substitute for a healthy balanced diet," said Dr Fang Fang Zhang, the study's senior author.
"There's a belief that supplements can improve and maintain health, but this study provides more evidence that there are no benefits," added Zhang. She's an associate professor at the Tufts University School of Nutrition Science and Policy in Boston.
Zhang said it wasn't clear why nutrients from supplements didn't provide the same benefits they do when they're found in food.
"Supplement forms could just have different effects than the natural form. In food, the body can regulate and limit the absorption of nutrients. In supplements, the body doesn't have the same regulatory impact," she said.
Zhang did note that the population in this study was generally healthy, so the findings don't necessarily apply to people who are deficient in certain nutrients.
Vitamin C most commonly used
The study included more than 27 000 US adults aged 20 or older. They answered questions about their dietary supplement use and their diets.
More than half reported using at least one supplement, and more than one-third used a multivitamin. Supplement users were more likely to be female, white and have higher levels of education and income. They were also more likely to eat a healthy diet and be physically active.
Vitamin C was the most commonly used supplement, followed by vitamin E, calcium and vitamin D, according to the report.
So is it time to clear out the cabinets and toss all of your supplements?
Zhang said if you're healthy, supplements aren't recommended. But if you've been diagnosed as deficient in a certain nutrient, don't stop taking it without talking to your doctor, she advised.
Samantha Heller is a registered dietitian at NYU Langone Health who wasn't involved in the study.
A very delicate balance
"No single nutrient is going to solve our health issues. But there are times where supplementation with vitamins or minerals is necessary and important," said Heller.
For example, people who are living a vegan lifestyle may come up short on vitamin B12, vitamin D and omega-3 fatty acids, she explained. And she said that vitamin D insufficiency is a global problem, though there's no consensus among health experts as to how much vitamin D people should take.
"Supplements can be helpful when necessary, but there are people who feel that if a little is good, more is better. Our bodies work at maintaining a very delicate balance, and taking too much of any one nutrient can knock that balance off," Heller said.
The bottom line, according to both experts, is that everyone should get most vitamins and minerals from foods.
"No single supplement can include all of the amazing plant compounds contained in fruits and vegetables, legumes, nuts and seeds, and whole grains," Heller said. "The nutrients in foods work synergistically to help keep us healthy and fight disease."
The study findings were published online in the Annals of Internal Medicine.
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