Jury still out on vitamin, mineral supplements to prevent heart disease, cancer

There is, however, enough evidence to recommend that people do not take beta-carotene or vitamin E to prevent those conditions, the U.S. Preventive Services Task Force (USPSTF) concludes.

The updated recommendations, published in JAMA, are consistent with the panel's 2014 recommendations on vitamin, mineral and multivitamin supplements to prevent cardiovascular disease (CVD) and cancer. They are based on 84 studies, including 52 new ones since 2014.

The recommendations apply to community-dwelling, nonpregnant adults. They do not apply to children, persons who are pregnant or may become pregnant, or persons who are chronically ill, are hospitalized, or have a known nutritional deficiency.

CVD and cancer are the top two causes of death in the U.S., and vitamin and mineral supplementation has been proposed to help guard against these conditions.

Yet the latest evidence suggests that vitamin and mineral supplementation is associated with "little or no benefit" in preventing cancer, CVD and death, the panel says.

Last year Americans spent close to $50 billion on dietary supplements, while the dietary-supplement industry spent about $900 million on marketing, Dr. Jeffrey A. Linder, with Northwestern University Feinberg School of Medicine in Chicago, notes in a JAMA editorial.

"Most people view supplements as, at worst, benign preventive products," he points out. However, in the U.S., dietary supplements are relatively unregulated and required to state that health claims have "not been evaluated by the Food and Drug Administration" and they are "not intended to diagnose, treat, cure, or prevent any disease."

"Individual, public health, public policy, and civic efforts should focus on supporting people in regular preventive care, following a healthful diet, getting exercise, maintaining a healthy weight, and avoiding smoking. Health systems and health care professionals should focus on evidence-based preventive services recommended by the USPSTF, including controlling high blood pressure and behavioral counseling to encourage physical activity and a healthy diet," Dr. Linder advises.

In a separate editorial in JAMA Internal Medicine, Dr. Peter Ubel with Duke University, in Durham, North Carolina, notes that supplement advertisements often state that potential vitamin deficiency may include fatigue, low motivation, and thinning hair.

"As if that message does not resonate with enough people, they label their products with enticing names like 'True Strength,' 'Core Nutritionals' (6- pack abs around the corner), and 'Immortal Elite Vitamin Pack' (because who would want to gain immortality in anything other than an elite manner?)."

"Essential nutrients plus clever marketing: it is clear why vitamin and mineral supplements are so appealing. But that begs the question of why it is so easy to market the unproven benefits of these products while it is so difficult to convince people to receive lifesaving vaccines," Dr. Ubel writes.

He says while the USPSTF has "brilliantly" synthesized evidence about the health effect of vitamin and mineral supplements, "the work is not over. If we want people to stop taking unnecessary vitamins and start receiving lifesaving vaccines, we need to address the psychological (and political) factors that cause people to embrace evidence-incongruent beliefs."