Please don't groan. Yes, this is one more of those confusing studies that seem to flip-flop the previous confusing studies. But let's just file it away as a valuable data point in an evolving picture, and rejoice that at least, as these studies get bigger and better, the findings should become stronger.
Last we heard — last fall, actually — a study of more than 38,000 older women in Iowa brought disturbing news to the millions who take daily vitamins. It found, as NPR reported: "Use of many common supplements — iron, in particular — appeared to increase the risk of dying, and only calcium supplements appeared to reduce mortality risk. The increased risk amounted to a few percentage points in most instances."
Now comes a somewhat countervailing study: The Journal of the American Medical Association reports that in 15,000 older men, multivitamins do confer apparent benefit, reducing the total risk of cancer by 8 percent. I spoke with the study's co-author, Dr. Howard Sesso, an associate professor of medicine at Brigham and Women's Hospital. He acknowledged my flip-flip complaint, but noted that this latest study does take the research up a notch:
Previous multivitamin studies have been "observational studies," he said. "These are free-living populations, and they take multivitamins or they don't," and the researchers would try to control for the pre-existing differences between vitamin takers and non-takers.
This new research, he said, is different in that among the 15,000 men in the Physicians' Health Study, it randomly assigned men to take vitamins or a placebo, for an average of 11 years. So it's longer-term than previous studies, and it is "the first long-term randomized trial that tested whether daily multivitamin use prevents cancer."
In a few weeks, he noted, the researchers will also present data on vitamins' effects on heart and blood-vessel health. And in a months, on eye disease and cognitive function.
The vitamins' effect on cancer was "modest — an 8% reduction in the risk of total cancer for men who took a multivitamin — but it was significant," he said. And it's important information "given how little we know about the prevention of cancer in general."
Is there any reason to think the effect in women might be different? "We just don't know," he said; just as we don't know whether it would be similar in younger men and various racial and ethnic groups.
So, I asked, what's the takeaway for whether I should take a multi-vitamin? (I stopped after last year's study, and now take just a baby aspirin and Vitamin D.)
"It's an important question," Dr. Sesso answered. "The number one reason to consider taking a multi-vitamin is to prevent vitamin and mineral deficiency; so if you don't have the best diet, a multi-vitamin can step in to provide the low levels we need as a minimum to prevent deficiency."
The study goes a step further, he noted, in that many people take vitamins not because they're nutrient-deficient but because they think it might help their health in other ways, and the findings can add some data to that decision.
Bottom line: "It still is something you should always discuss with your primary care provider, and it still is an individual choice, and it depends on your dietary status, your health status..." In the study, he added, "There were about 1300 men who did have a history of cancer at the start of the study; we found a suggestion, though not definitive, a suggestion that men with a history of cancer may have a greater reduction of risk than men without it. So it's important to think about your own individual situation."
Financial note: The study was supported mainly by the National Institutes of Health. But the press release adds an industry collaboration as well:
This work was supported by grants from the National Institutes of Health and an investigator-initiated grant from BASF Corporation. Study agents and packaging were provided by BASF Corporation and Pfizer (formerly Wyeth, American Home Products, and Lederle), and study packaging was provided by DSM Nutritional Products, Inc. (formerly Roche Vitamins).
Stats from the press release:
The trial includes 14,641 male U.S. physicians, initially age 50 years or older, including 1,312 men with a history of cancer at randomization, who were enrolled in a multivitamin study that began in 1997 with treatment and follow-up through June 1, 2011. Participants received a daily multivitamin or equivalent placebo. The primary measured outcome for the study was total cancer (excluding nonmelanoma skin cancer), with prostate, colorectal, and other site-specific cancers among the secondary end points.
PHS II participants were followed for an average of 11.2 years. During multivitamin treatment, there were 2,669 confirmed cases of cancer, including 1,373 cases of prostate cancer and 210 cases of colorectal cancer, with some men experiencing multiple events. A total of 2,757 (18.8 percent) men died during follow-up, including 859 (5.9 percent) due to cancer. Analysis of the data indicated that men taking a multivitamin had a modest 8 percent reduction in total cancer incidence. Men taking a multivitamin had a similar reduction in total epithelial cell cancer. Approximately half of all incident cancers were prostate cancer, many of which were early stage. The researchers found no effect of a multivitamin on prostate cancer, whereas a multivitamin significantly reduced the risk of total cancer excluding prostate cancer. There were no statistically significant reductions in individual site-specific cancers, including colorectal, lung, and bladder cancer, or in cancer mortality.
Daily multivitamin use was also associated with was a reduction in total cancer among the 1,312 men with a baseline history of cancer, but this result did not significantly differ from that observed among 13,329 men initially without cancer.
Readers, lingering questions?
This program aired on October 17, 2012. The audio for this program is not available.