Q: Are any supplements proven to be helpful for health?
The U.S. dietary supplement industry has exploded in the last 30 years, growing from about 4,000 products in 1994 to more than 95,000 on the market today, according to the Food and Drug Administration. These capsules, powders, gummies and tinctures are often labeled with big — if vague — claims like “supports immune health” or “improves brain performance.”
But most supplements have not been rigorously tested for safety or effectiveness, said Dr. JoAnn Manson, a professor of medicine at Harvard Medical School.
And when researchers have tested them, she added, they haven’t typically found the health benefits they’d hoped for, and sometimes have even found some risks.
But, she said, there are some instances where taking a supplement may improve your health. Here are some of the main ones.
To Treat or Prevent a Nutrient Deficiency
If a blood test reveals that your body is low in a particular vitamin or mineral, such as vitamin D or iron, supplements can be “essential” in correcting that deficiency, said Dr. Pieter Cohen, an internist at Cambridge Health Alliance in Somerville, Mass.
People who follow a vegan diet or have a condition called pernicious anemia are at greater risk of a vitamin B12 deficiency and may benefit from taking a supplement. And breastfed infants should receive vitamin D and iron supplements, according to the American Academy of Pediatrics.
If you have difficulties absorbing nutrients from food, which can happen after you’ve had bariatric surgery or if you have a medical condition like celiac disease, Crohn’s disease or ulcerative colitis, a supplement may be recommended, Dr. Cohen said.
If You Are or May Become Pregnant
It’s important to take 400 to 800 micrograms of folic acid per day if you could become pregnant and during the early months of pregnancy to prevent major birth defects, said Dr. John Wong, a professor of medicine at Tufts University School of Medicine.
Most prenatal multivitamins, which should be taken throughout pregnancy, contain this amount, and also supply other key nutrients such as iron, calcium and vitamin D.
If You’re in Middle or Old Age
Most older adults usually get enough nutrition from their food. But as you age, your requirements for some nutrients increase while your ability to absorb them and your appetite can diminish, so your doctor may recommend a supplement. Older adults may have trouble absorbing vitamin B12, for example. And you may need a calcium and vitamin D supplement if you’re at risk for bone loss, Dr. Manson said.
There are hints from research that a few other supplements may help prevent certain health conditions. In one 2019 study of adults 50 or older, Dr. Manson and her colleagues found that for participants who rarely or never ate fatty fish, those who took an omega-3 fatty acid supplement had fewer cardiovascular events like heart attacks or strokes than those who took a placebo. Those who took vitamin D were also less likely to develop autoimmune diseases like rheumatoid arthritis and psoriasis.
Several recent trials have also found that multivitamins may improve memory and slow cognitive decline in older adults, though more research is needed, Dr. Manson said.
And there’s some evidence that taking a supplement that contains vitamins C and E, zinc, copper, lutein and zeaxanthin (called an AREDS supplement) can slow vision loss for those with age-related macular degeneration, Dr. Manson said.
In All Other Cases, Use Caution
Just because a supplement contains a nutrient or other natural compound doesn’t make it safe, especially if it has amounts far greater than what you would find in food, Dr. Manson said. And in some cases, they can even be harmful.
In the 1990s, for example, researchers hoped that antioxidant supplements like beta-carotene and vitamin E would prevent cancer or heart disease. But when tested in large trials, they found that beta-carotene increased the risk of lung cancer in some people, Dr. Wong said, and vitamin E increased hemorrhagic strokes in men, Dr. Manson added.
Little is known about the risks, benefits or correct dosing of many supplements, said Dr. Mahtab Jafari, a professor of pharmaceutical sciences at the University of California, Irvine.
And what’s listed on the package can also be different from what’s inside the product, Dr. Cohen said. For instance, many weight loss and sports supplements have been found to be tainted with unlisted drugs or chemicals.
If you do purchase supplements, look for a certification seal from a trusted third party organization such as the U.S. Pharmacopeia or NSF, which confirm that the products contain the ingredients listed on the label.
Always check with your doctor before taking a supplement, Dr. Jafari said, because they can interact with certain medications. Vitamin K can interact with a blood thinning medication, for example, and St. John’s wort can interfere with antidepressants and birth control pills.
Finally, Dr. Manson said, don’t expect supplements to be a substitute for eating well and being physically active.
“There’s no magic pill that is going to provide good health,” she said.
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