JAMA: Supplementing with a daily multivitamin reduces total cancer incidence

CHICAGO — In a randomized trial that included nearly 15,000 male physicians and started in 1997, long-term daily multivitamin use resulted in a modest, but statistically significant, reduction in cancer after more than a decade of treatment and follow-up, according to a study appearing in JAMA that was released Wednesday. The multivitamin used in the study was Pfizer's Centrum Silver. 

“Multivitamins are the most common dietary supplement, regularly taken by at least one-third of U.S. adults," wrote Michael Gaziano of Harvard Medical School. "The traditional role of a daily multivitamin is to prevent nutritional deficiency. The combination of essential vitamins and minerals contained in multivitamins may mirror healthier dietary patterns, such as fruit and vegetable intake, which have been modestly and inversely associated with cancer risk in some, but not all, epidemiologic studies," he continued. 

According to the Council for Responsible Nutrition, 52% of Americans take multivitamins, with 42% doing so regularly. Among physicians, 72% personally use dietary supplements, with multivitamins being the most prevalent supplement in this population. 

Analysis of the data indicated that men taking a multivitamin, versus placebo, had a modest 8% reduction in total cancer incidence. However, the researchers found no effect of a multivitamin on prostate cancer. “The reduction in total cancer risk … argues that the broader combination of low-dose vitamins and minerals contained in the multivitamin, rather than an emphasis on previously tested high-dose vitamins and mineral trials, may be paramount for cancer prevention," Gaziano wrote. 

“This study reinforces the value of long-term consistent use of a daily multivitamin as a convenient and affordable insurance policy for good health,” stated Duffy MacKay, VP scientific and regulatory affairs for the Council for Responsible Nutrition. Not only did this study provide good news for the supplement industry and its consumers, but it also provided another reminder that science should be viewed in the context of the full body of scientific literature, MacKay added. 

"This study … demonstrates the role of accessible and affordable consumer health products like multivitamins in cancer prevention," stated Scott Melville, president and CEO for the Consumer Healthcare Products Association. "Now more than ever, consumers should strive to maintain a healthy lifestyle with a balanced diet and exercise, and can continue to rely on vitamins to fill nutritional gaps and enhance health."

The researchers noted that total cancer rates in their trial were likely influenced by the increased surveillance for prostate-specific antigen and subsequent diagnoses of prostate cancer during follow-up starting in the late 1990s. “Approximately half of all confirmed cancers … were prostate cancer, of which the vast majority were earlier stage, lower grade prostate cancer with high survival rates. The significant reduction in total cancer minus prostate cancer suggests that daily multivitamin use may have a greater benefit on more clinically relevant cancer diagnoses," Gaziano noted.