What You Need to Know about Supplements

They may not contain what you think, and they’re not necessarily harmless.

Supplements can be expensive. So be sure you’re getting what you’re paying for and that there’s actual evidence that the supplement could help you — and won’t do harm. The belief that supplements are harmless because they’re “natural” is a myth. Nature has produced many poisons. Also, we’ve heard so much hype about “natural products” that it’s hard to remember those capsules you’re taking didn’t fall from a tree. They are manufactured, and often to your disadvantage.  

Because supplements aren’t regulated or tested like drugs, there’s no guarantee that their contents match the label, although manufacturers are responsible for ensuring their products are safe and the labels aren’t misleading. When Canadian researchers tested 44 popular herbal products from 12 companies in 2013, they found that a third had no trace of the plant on the bottle’s label — but another plant instead. The rest had been contaminated with other plants, or contained mostly fillers. The New York Attorney General's office has asked GNC, Target, Walmart, and Walgreens to stop selling their store brands for popular supplements after its own research found that almost 80 percent were contaminated or didn’t contain the correct plant.

You’re best off getting your nutrients from food, in any case. Over and over, when scientists identify a food that promises a health-boosting effect, the supplements manufacturers identify a particular ingredient that they can package to sell. But then research with people shows that the supplement didn’t help. The reason is that nutrients in food work together. If you isolate one nutrient and take too much of it, you can get in trouble. Too much vitamin A, for example, has been associated with osteoporosis and an increased risk of hip fractures.

Maybe you’re taking vitamins known as “antioxidants” — C and beta-carotene — to help prevent heart disease or cancer. You may have heard advice based on early lab studies, which suggested that higher antioxidant levels might prevent what’s called “free-radical damage,” tied to cancer. But most studies in people don't support that theory, says John Swartzberg, MD, chair of the editorial board of the University of California, Berkeley Wellness Letter. It’s possible that beta-carotene increases the risk of lung cancers in smokers. In fact, cancer patients are warned not to take any of these antioxidants because they could speed up the growth of the cancer or otherwise interfere with treatment.

We’d all love a cure for the cold. About 75 mg. of zinc in a lozenge or syrup may shorten the duration of colds by a day if you take it within 24 hours of the first cold symptom. But in higher doses taken regularly, zinc can impair the immune system. Swartzberg says you can forget about commercial formulas that contain a medley of supposed cold cures, including vitamin A.

What about taking “probiotics”? Researchers who study the gut say it could be helpful to eat foods considered “probiotics,” such as yogurt and natural sauerkraut, and more vegetables. Alas, the “Live & Active Cultures” seal from the National Yogurt Association (NYA) is only a promise that a refrigerated yogurt contains live cultures at the time of manufacture — not when you eat it. The Food and Drug Administration has not approved the seal, and the NYA doesn’t monitor products. Supplements again may not be as advertised. The independent testing company LabDoor reports on probiotics brands. But it’s also not yet clear which of the many strains called “probiotics” is best for which purpose.

The greatest risk: you’ll take useless supplements rather than more effective action. For example, people who learn that they carry a gene related to Alzheimer’s risk are more likely to take ginko biloba, which has not been proven effective to prevent dementia. They’d be much better off increasing their exercise, which does seem to help.