Studies on health benefits of vitamins, supplements bring different conclusions

Paul Washington spends about $50 a month on vitamins and other supplements because “you always want to maintain an optimum level of health.”

The 65-year-old Wheatley Heights man is among 1 in 2 Americans who buy supplements, many with the hope of staying healthy and living longer. Yet, many of the boastful claims on the labels of the dizzying variety of supplements that line drugstore shelves are not supported by scientific research, experts say.

Studies on potential health benefits of supplements sometimes come to different conclusions, and experts don’t always agree on which — if any — vitamins are helpful.

That confuses consumers such as Washington.

“One year they’re saying one thing, and another year they’re saying another thing,” he said.

Washington takes a multivitamin daily, as well as supplements such as Ginkgo biloba, an extract from leaves of the ginkgo tree. Two brothers had recommended ginkgo for better memory, although most studies have concluded it does not improve memory or prevent memory loss. Washington said he does online research on supplements before taking them.

Washington knows a supplement is just that — a supplement to a nutrient-rich diet and exercise.

The problem, said Harvard Medical School professor Dr. JoAnn Manson, is that “people want to take a magic pill” and may focus more on those pills to stay healthy than on a good diet and exercise, which are the real keys to good health.

Some supplements can even harm you, especially if taken in large quantities or if mixed with prescription drugs.

Here are answers to some common questions about supplements.

Will vitamins and other supplements make me healthier?

There’s not complete agreement on this. A 2013 editorial in the Annals of Internal Medicine written by five physicians said, “Most supplements do not prevent chronic disease or death, their use is not justified, and they should be avoided.”

Yet Carol Haggans, an expert on vitamins and a consultant to the National Institutes of Health’s Office of Dietary Supplements, said that “if you are not getting enough of a particular nutrient from your diet for whatever reason … and you’re at risk of a deficiency or even a marginal intake, then supplements can certainly help fill those gaps.”

Why do doctors disagree on whether certain vitamins and supplements are advisable?

“One of the reasons is there are very few large, rigorous, randomized trials of these vitamin supplements, particularly multivitamin supplements, on whether they prevent cancer, cardiovascular disease and other chronic diseases,” said Manson, a researcher in what she described as the only large-scale, randomized trial of multivitamins.

That study, released in 2012, found that male doctors 50 and older who took multivitamins were 8 percent less likely to develop cancer than those who did not. Manson is a principal investigator of a current multivitamin study that is studying a broader group of both women and men.

What about studies that concluded multivitamins were not beneficial?

“Many of those studies didn’t ask the right questions,” said Dr. Brent Bauer, director of the Complementary and Integrative Medicine Program at the Mayo Clinic in Rochester, Minnesota. “They took healthy people and gave them a multivitamin and said it didn’t work.”

A better design for a multivitamin study would focus on people who don't get enough nutrients in their diets, such as people who primarily eat fast food, said Chris D’Adamo, director of research and education at the University of Maryland Medical School’s Center for Integrative Medicine.

So if I eat a lot of greasy food and avoid vegetables, maybe some study will conclude that all I need to do is take vitamins and I’ll be fine?

No. Experts say a good diet and exercise are far more important than supplements. D'Adamo said you should only take multivitamins “sort of as an insurance policy.”

For healthy people with diets rich in fruits, vegetables, whole grains and fish, and low in red meat and processed foods, “There’s very little evidence [supplements are] going to improve their health,” Manson said.

Why is it usually better to get vitamins through food than through pills?

The body absorbs most nutrients from food better than it does from vitamins in pill form, Manson said.

But B12, folic acid and some other nutrients are absorbed better when consumed as supplements or in foods fortified with the nutrients, Haggans said.

Nutritious food has benefits beyond vitamins. For example, unlike a vitamin C pill, an orange has fiber and other beneficial substances, and it’s good for your digestion, Bauer said.

It is likely this combination of vitamins and other substances in food that explains why higher consumption of fruits and vegetables is associated with a lower risk of many forms of cancer, “but the same doesn’t hold true when you isolate some of the different components of fruits and vegetables,” Haggans said.

Who might benefit from supplements?

Pregnant women may benefit from vitamins with folic acid, breast-fed infants may need a vitamin D supplement, and some older adults could benefit from a B12 supplement, Manson said. People with certain medical conditions also may benefit from specific supplements.

Can supplements be bad for me?

Yes. For example, a high amount of beta carotene is linked to an increased risk of lung cancer in smokers, and too much vitamin D may increase the risk of kidney stones, Bauer said. And although some studies have shown St. John’s wort may help people with mild depression, it also can have dangerous interactions with some medications, including anti-depressants, and it can make drugs like birth control pills less effective.

A multivitamin is unlikely to have a high enough level of any nutrient to cause harm, Haggans said. But some capsules containing a single vitamin or mineral are so highly concentrated that they could pose health risks, she said.

Some supplement labels make a lot of impressive health claims. Are those claims true?

Not necessarily. The federal government allows manufacturers to say a product improves health, even if there is no scientific study that proves it does.

For example, bottles of Ginkgo biloba say the substance “helps support healthy circulation, memory and mental focus.” Yet the National Institutes of Health says “there is no conclusive evidence that ginkgo is helpful for any health condition.”

Health claims for supplements typically have an asterisk next to them that is linked to this federally mandated disclaimer: “This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease.”