- In 2002, "The Journal of the American Medical Association" published a paper by Robert. H. Fletcher and Kathleen M. Fairfield of the Harvard School of Medicine which concluded that based on a meta-analysis of 36 years' worth of published studies on the efficacy of taking multivitamins to prevent disease, "it appears prudent for all adults to take vitamin supplements."
- To the contrary, a 2006 report prepared by Johns Hopkins University for the U.S. Department of Health and Human Services stated that "regular supplementation with a single nutrient or a mixture of nutrients for years has no significant benefits" in the prevention of disease.
- Alarmingly, a 2007 Consumer Lab investigation found that of 21 brands of multivitamins tested by independent labs, only 10 met stated claims on their labels regarding nutritional contents, and one product was even contaminated with lead.
- Despite the risks of taking supplements, many Americans may be deficient in a key nutrient. According to a 2009 article published in "Archives of Internal Medicine", close to three quarters of Americans are deficient in vitamin D, and further research of vitamin D supplementation is recommended.
- Some doctors recommend a balanced approach of taking vitamins to supplement, but not to replace, a healthy diet and lifestyle. According to Dr. David Katz, director of the Yale Prevention Research Center, vitamins are "not a substitute for getting your vitamins from fruits and vegetables, but everyone should take them as more of an insurance policy."