5 Popular Supplements That May Have Hidden Dangers
When it comes to supplements, there’s so much hype about their potential benefits that it can be hard to separate fact from fiction. While it’s true that vitamins and minerals are essential to health, it’s not true that taking them in pill, capsule, or powder form — especially in megadoses — is necessary or without risks.
For one thing, dietary supplements can sometimes interact with each other, as well as with over-the-counter (OTC) and prescription medication. In addition, unlike with drugs, the U.S. Food and Drug Administration (FDA) is not authorized to review dietary supplements for safety and effectiveness before they are marketed. It’s up to manufacturers to ensure that their products do not contain contaminants or impurities, are properly labeled, and contain what they claim. In other words, the regulation of dietary supplements is much less strict than it is for prescription or OTC drugs.
In March 2023, the FDA unveiled its new Dietary Supplement Ingredient Directory, a web page intended to help the public stay informed about the ingredients used in dietary supplements. Consumers can use the directory to look up ingredients used in products marketed as dietary supplements and find out what the FDA has said about that ingredient and whether the agency has taken any action pertaining to the ingredient.
According to the FDA, more than half of Americans take herbal or dietary supplements daily, with a report by Grandview Research noting the dietary supplements market was valued at $151.9 billion worldwide in 2021.
1. Vitamin D: Too Much Can Harm Your Kidneys
Vitamin D promotes calcium absorption in the body, and having enough is central to health and well-being, offering the promise of protecting bones and preventing bone diseases like osteoporosis, per the NIH. Supplemental vitamin D is popular because it’s difficult (if not impossible for some) to get enough from food.
Also, as the Centers for Disease Control and Prevention (CDC) notes, our bodies make vitamin D when bare skin is exposed to direct sunlight, but increased time spent indoors and widespread use of sunblock, as a necessary way to prevent skin aging and skin cancer, has minimized the amount of vitamin D many of us get from sun exposure.
2. St. John’s Wort: Avoid Drug Interactions
St. John’s wort is a plant used as a tea or in capsules, with purported benefits for depression, attention-deficit hyperactivity disorder, menopause symptoms, insomnia, kidney and lung issues, obsessive-compulsive disorder, wound healing, and more, notes the NIH.
Small studies have shown St. John’s wort to be effective at treating mild depression. For example, a review of short-term studies looked at 27 clinical trials with about 3,800 patients and suggested that the herbal remedy worked as well as certain antidepressants at decreasing symptoms of mild to moderate depression.
But, says Denise Millstine, MD, an internist in the department of integrative medicine at Mayo Clinic in Phoenix, Arizona, “the biggest issue with St. John’s wort is its medication interactions.”
3. Calcium: The Excess May Settle in Your Arteries
Calcium is essential for a strong skeleton, but as with all nutrients, too much of this mineral may be harmful. As the NIH notes, more than 2,500 mg per day for adults ages 19 to 50, and more than 2,000 mg per day for individuals 51 and over, can lead to problems.
With calcium supplements, hardened arteries, or atherosclerosis, and a higher risk of heart disease, are risks, though research is mixed, according to the Cleveland Clinic.
4. Multivitamins and Multiminerals: No Substitute for a Healthy Diet
Think that a healthy lifestyle requires not just good-for-you foods, exercise, and enough sleep but also taking a daily multivitamin-multimineral supplement? When you consider that an estimated one-third of adults in the United States and one-quarter of youths take them, per the NIH, you may be surprised to learn that the jury’s still out on whether they’re helpful.
One study published in the journal JAMA Internal Medicine, which examined data from nearly 40,000 women older than 19 who were part of the Iowa Women’s Health Study, found that, on average, women who took supplements had a higher risk of early death than women who didn’t take supplements. Multivitamins did little or nothing to protect against common cancers, cardiovascular disease, or death.
Other research has found benefits to taking multivitamins. For example, a study in the August 2017 Nutrients concluded that frequent use of multivitamin and mineral supplements helped prevent micronutrient shortfalls that might otherwise cause health problems.
5. Fish Oil Supplements: Choose Fish or Flaxseed Instead
Rich in omega-3 fatty acids, fish oil has been touted as a means to reduce heart disease and other ailments. Yet increasing evidence suggests that fish oil supplements have questionable benefits.
For example, a study published in January 2019 in the New England Journal of Medicine found that omega-3 supplements did nothing to reduce heart attacks, strokes, or deaths from heart disease in middle-aged and older men and women without any known risk factors for cardiovascular disease. An earlier study analyzed people at high risk for cardiovascular disease and also reported no benefit.
Plus, a later review and meta-analysis of 83 randomized controlled trials, which was published in August 2019 in the journal BMJ, revealed that omega-3s, whether in supplement or food form, didn’t reduce type 2 diabetes risk among the 58,000 participants involved.
But it’s not all negative news when it comes to omega-3 supplements: A large randomized controlled trial published in January 2022 in BMJ suggests that fish oil supplements may provide health benefits when combined with vitamin D supplements, though in this case the benefits weren’t statistically significant. The authors observed that this cocktail, as well as vitamin D supplements alone, led to a lower incidence of autoimmune conditions such as psoriasis and rheumatoid arthritis.