Key Takeaways:
- Vitamin E and beta‑carotene pills do not prevent cancer or heart disease in people who are otherwise healthy.
- Some supplements, such as St. John’s wort, can interfere with prescription drugs.
- Only a few nutrients—like folic acid during pregnancy and vitamin D for certain groups—have proven necessity.
Dietary supplements are widely used across the United States, yet many experts suggest they largely represent spent money instead of meaningful health benefits.
Multivitamins rank among the most common purchases, but peer‑reviewed studies rarely show clear declines in disease risk or overall death rates for healthy adults.
The U.S. Preventive Services Task Force advises against taking vitamin E or beta‑carotene supplements to lower heart disease or cancer risk in those without existing health problems.
According to Dr. John Wong, a Tufts health professor who serves on the Task Force, vitamin E offers no protection against either cancer or cardiovascular disease.
Beta‑carotene, which the body converts to vitamin A, can actually raise the chance of lung cancer among smokers or workers exposed to asbestos.
Beyond safety concerns, supplements may also affect how your normal medications work. For instance, St. John’s wort, a herb used for depression and insomnia, can alter the effectiveness of birth control pills.
Even when supplements do not cause harm, the excess amounts many people consume can be superfluous, as the body simply does not need them.
Despite this, Americans continue to spend billions on supplements each year.
“People prefer a tangible approach to health; taking a pill feels easier than changing diet and lifestyle,” explains registered dietitian Melissa Majumdar of Emory University Hospital.
Before starting any supplement, it is wise to scrutinize the label for potentially misleading health claims. The Food and Drug Administration does not evaluate supplements for safety or efficacy, and some product claims—such as offering “no side effects” or “beyond prescribed drugs”—are not verified.
The Task Force does give a grade “A” for folic acid (vitamin B9) in pregnant adults because it lowers the risk of certain birth defects. Because many foods are fortified, the challenge remains to assure adequate intake through diet alone.
Vitamin D is another nutrient that many people cannot acquire fully from sunlight and diet. Individuals with darker skin, those living in northern latitudes, or those who avoid sun exposure may fall short.
“Vitamin D deficiency is common in those groups,” notes Dr. Emma Laing of the University of Georgia and spokesperson for the Academy of Nutrition and Dietetics.
However, too much vitamin D can lead to complications such as kidney problems or neurological symptoms. A blood test can help determine whether supplementation is necessary.