Research published in the Archives of Internal Medicine concluded that multivitamin use has little or no influence on the risk of common cancers, cardiovascular disease (CVD) or total mortality in postmenopausal women.

The study evaluated data from 161,808 participants enrolled in the Women’s Health Initiative clinical trials (N = 68,132 in three overlapping trials of hormone therapy, dietary modification and calcium and vitamin D supplements), as well as 93,676 women from an observational study. Detailed information was collected on multivitamin use and subjects were followed for an average of about eight years.

The study documented cancers of the breast (invasive), colon/rectum, endometrium, kidney, bladder, stomach, ovary and lung; CVD (myocardial infarction, stroke and venous thromboembolism); and total mortality.

After a median of about eight years, analyses revealed no association of multivitamin use with risk of cancer, according to the study. A total of 41.5% of the participants used multivitamins. After follow-up, 9619 cases of breast, colorectal, endometrial, renal, bladder, stomach, lung or ovarian cancer; 8751 CVD events; and 9865 deaths were reported.

However, critics say the study fails to account for important dietary factors or adequately grasp how dietary supplements and health claims are regulated. “While cohort and observational studies like these can be important, they in no way constitute convincing or conclusive evidence,” said Daniel Fabricant, PhD, vice president of scientific and regulatory affairs for the Natural Products Association, Washington, D.C. “This study fails to tell the whole story about the positive affect that vitamins and minerals can have on health. It also does not take into account important factors such as nutrients gained through diet.” 

Mr. Fabricant said it is “unprincipled” that the authors arbitrarily lumped supplement types into generalized categories that do not represent nutrient intake accurately. And when coupled with the fact that nutrient intake through the diet was not accounted for, Fabricant explained, the study has no means of establishing a baseline for which to draw any comparisons or eliminate bias.

Also troubling was the author’s apparent lack of understanding about how dietary supplements are regulated, he added. “The authors seem to be confused or unaware of how supplements are regulated and exactly what constitutes a health claim authorized by the FDA. For example, they cite that there is only one supplement, folic acid, worthy of a public health recommendation by way of a health claim. However, even a cursory visit to the FDA’s website would have revealed that other nutrients and dietary ingredients, including the very calcium and vitamin D that they studied, also have FDA-authorized health claims.”

Taken as whole, research on dietary supplements in the prevention of chronic diseases, has been strong and consistent, said Mr. Fabricant. “To suggest that taking vitamins and minerals with a demonstrated health benefit is unnecessary sends the wrong public health message.”

Andrew Shao, PhD, vice president, scientific and regulatory affairs with the Washington, D.C.-based Council for Responsible Nutrition (CRN), said multivitamins, like all other dietary supplements, are meant to be used as part of an overall healthy lifestyle.

“As the authors themselves point out in this study, people who use multivitamins are likely to be healthier and engage in many healthy habits, including being more physically active, having a higher fruit and vegetable intake, consuming lower amounts of fat, and are less likely to smoke,” he said. “In other words, the key to good health is a commitment to an overall wellness approach and that includes daily use of a multivitamin.”

According to the 2007 ‘Life…supplemented’ Healthcare Professionals Impact Study, almost half of physicians and nurses who take supplements most often do so for “overall health/wellness benefits,” he noted, while 41% of physicians and 62% of nurses who recommend supplements most often do so for the same reason.

“From a practical standpoint, this study does not change the fact that the majority of consumers could benefit from taking an affordable multivitamin, particularly as the majority of Americans fail to consume the recommended amounts of a variety of essential nutrients established by the Institute of Medicine,” said Dr. Shao. “It is better to meet these recommendations than not, and consistently taking a multivitamin over the long-term, could help fill these nutrient gaps and may help consumers lead healthier lives.”