There is a common misperception that all supplements are good and that if a little is good, then more is better. To date, there has been little evidence that dietary supplements reduce the risk of cancer—and now new research indicates that high doses of some supplements actually increase cancer risk, according to a commentary published in the Journal of the National Cancer Institute.
In fact, the data indicates that the true biology of dietary supplements is complex—and that the value of any nutrient cannot be assessed in isolation. The nutrients in dietary supplements are essential and have value; however, they often have value in a certain balance with other nutrients.
The data indicates that nutrients like beta-carotene, selenium, and folic acid are fairly harmless, even when taken up to three times the recommended daily allowance; however, when taken at higher levels, these three supplements have been shown to increase the risk of certain cancers.
The researchers suggest that stricter regulation may be necessary in order to ensure safe doses of nutrients. The U.S. Food and Drug Administration (FDA) regulates dietary supplements as food; however some supplements can act more like drugs, especially when taken at high doses.
Individuals who are concerned about getting the proper balance of nutrients are advised to eat a healthy, balanced diet with a wide variety of fruits and vegetables. Most people who consume a healthy diet should not need to supplement.
Martinez ME, Jacobs ET, Baron JA, et al. Dietary Supplements and Cancer Prevention: Balancing Potential Benefits Against Proven Harms. Journal of the National Cancer Institute. 2012; 104(10): 732 DOI: 10.1093/jnci/djs195