Some people benefit, but for many it could be a waste of money.

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On Nutrition

Every year, the dietary-supplement industry brings in billions of dollars, with an estimated 90,000 products on the market. Indeed, I can’t go to Costco without seeing carts heavily laden with supplements. Multivitamins, taken by more than 1 in 3 Americans according to the National Institutes of Health, fall under that profitable umbrella. If you pop a daily multi, odds are you want to improve your health or prevent chronic disease. But in 2014, the U.S. Preventive Services Task Force stated that evidence didn’t support taking — or avoiding — multivitamins. So are you wasting your money?

One problem with research on multivitamins is that “multivitamin” can mean many things. Multivitamins may have as few as two micronutrients (vitamins and minerals), and the amounts of each nutrient may be tiny, or excessive. Many recent studies using multivitamins with 10 or more vitamins and/or minerals have shown mild to moderate benefits for reducing risk of chronic disease in some cases. One of these, the long-running Physicians Health Study (PHS), randomly assigned about 14,600 male U.S. physicians aged 50 or older to take either a multivitamin or a placebo daily for 12 years. The results suggested that taking a multivitamin doesn’t reduce risk of cardiovascular disease or improve cognitive health, but may reduce cancer risk.

But that study didn’t include women.

Fortunately, another large study is under way to clarify any benefits of multivitamins on reducing cancer and cardiovascular-disease risk in both women and men. The COcoa Supplement and Multivitamin Outcomes Study (COSMOS) will randomly assign 22,000 women age 65 or older and men age 60 or older a common multivitamin or a placebo for four years.

In the meantime, a systematic review published earlier this month in the journal Circulation concluded that taking a multivitamin or mineral supplement doesn’t improve cardiovascular health in the general population.

Health insurance

Many think it’s good “insurance” to take a multivitamin, even though there’s no evidence that people who are eating a healthful diet should. Healthful eating can’t be reduced to isolated nutrients, which is why food, with its complex interplay of multiple micronutrients, macronutrients (carbohydrates, protein and fat) along with other bioavailable compounds, is the best vehicle for our nutrition needs. Ironically, most multivitamin users already eat a balanced, nutrient-rich diet.

That said, some people benefit greatly from supplementation. The U.S. Dietary Guidelines for Americans has noted serious shortfalls in calcium, vitamin D, fiber and potassium, and evidence supports the value of prenatal vitamins and supplementation of specific nutrients for individuals who don’t absorb them well. It also points out that many people have diets that fall short on many essential nutrients, and a multivitamin can fill in the gaps. This includes people who are on low-calorie diets, have a poor appetite, or avoid certain food groups. Other people may have specific nutrient needs that are difficult to meet even with a nutritious diet. For example:

Safety and quality

A 2015 Consumer Reports survey found that most people think that dietary supplements are vetted for safety by the U.S. Food and Drug Administration (FDA). Not true. Unlike prescription or over-the-counter drugs, which must be approved by the FDA before they can be marketed, the FDA is not authorized to review dietary supplements for safety and effectiveness. The FDA can take action if it receives reports that a supplement already on the market is causing harm, but this can take several years. As far as dietary supplements go, we’re living in the Wild West.

I’ve frequently had patients bring a bag of supplements with them to an appointment, only to be shocked when I tell them that most of them are effectively worthless. A typical response: “But the label says that it does X, Y and Z. They can’t lie about that!”

Oh yes, they can.

Dietary-supplement labels are allowed to claim that the product addresses a nutrient deficiency, supports health or is linked to a particular body function (like immunity, bone health, heart health or cognitive function), but that claim may not necessarily be backed up by scientific evidence. If a supplement puts a health claim on its label, it’s also supposed to include a disclaimer: “This statement has not been evaluated by the FDA. This product is not intended to diagnose, treat, cure, or prevent any disease.” Unfortunately, there are too many supplements on the market for the FDA and the Federal Trade Commission to address all false or misleading claims.

What about independent testing? Doesn’t a “stamp” on the label assure that a supplement is safe and high-quality? Think again. Only a few stamps really mean something, and it may not be what you think. Several independent organizations — notably U.S. Pharmacopeia (USP), ConsumerLab and NSF International — offer quality testing. Their seals mean that the supplement was properly manufactured, contains the ingredients listed on the label, and doesn’t contain harmful levels of contaminants. They don’t guarantee that a product is safe or effective. Some major brands don’t use third-party testing because they have strong internal standards.

The bottom line

Don’t take single supplements without an identified need, because more of certain nutrients is not better. If you want to take a multivitamin, choose one tailored to your age, gender and other circumstances, such as pregnancy. This can help you get the right amount of key nutrients, but keep in mind that most multivitamins don’t contain enough of nutrients we may need, including calcium, magnesium and vitamin D, and most don’t contain choline. They also don’t contain beneficial food components like omega-3 fatty acids and phytonutrients.