Vitamins

Fruits and vegetables are nature’s vitamins, so adding additional supplements can be toxic — several studies have linked multivitamins to heart attacks and even shorter lifespans. Other risks include irregular heartbeat, pain and seizures, according to the NIH. (Thinkstock/Ablestock.com)

Taking vitamin D supplements will not improve bone mineral density or reduce fracture risk, a large meta-analysis involving more than 4,000 adults that's published inThe Lancetfound.

Instead, your best bet for bone health? Time spent outdoors in sunlight and a healthy diet, researchers said.

This is consistent with previous findings, Clifford J. Rosen, MD, a professor of medicine at Tufts University, told Weather.com. Dr. Rosen wrote in a commentary accompanying the study that dietary vitamin D combined with calcium in elderly adults does have a protective effect, however.

This signals that most healthy adults don't need vitamin D supplements, Dr. Rosen and the study authors agree, though close to half of adults aged 50 and older take one.

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"This is not to say that raising your vitamin D level might not have other health impacts, such as a lower risk of heart disease or cancer," Dr. Rosen said. "But that data is very limited." There have been many observational studies on vitamin D and heart disease or cancer risk, he said. But there are not many randomized controlled trials that confirm a link.

"Try to get vitamin D through your diet," he said. "As long as you're consuming adequate amounts in your diet, you don't need supplementation." A daily multivitamin combined with a generally healthy diet provides more than enough vitamin D for most people, he said. Adults need just 600 IUs of vitamin D a day, according to IOM recommendations. Those with a high bone fracture risk need about 800.

Vitamin D has been added to milk, orange juice and cereals. It's naturally found in fish, eggs and some mushrooms. Just 10 minutes a day of casual sun exposure (face and hands only) during the summer is enough to provide an adequate amount of vitamin D, according to the IOM recommendations. In high-latitude areas such as Dr. Rosen's native Maine, evidence has shown that both kids and adults don't get adequate vitamin D in the winter because the sun's rays are so diminished. But during that time, a healthy diet and multivitamin can compensate, Dr. Rosen said.

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"A lot of people are taking high amounts of vitamin D supplements because they think it doesn't hurt," Dr. Rosen said. "I'm not sure that that's a great rationale."

Similarly, the authors of the new study concluded, “This systematic review provides very little evidence of an overall benefit of vitamin D supplementation on bone density. Continuing widespread use of vitamin D for osteoporosis prevention in community-dwelling adults without specific risk factors for vitamin D deficiency seems to be inappropriate.”

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