In a randomized trial that included nearly 15,000 male physicians, 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.
"Observational studies of long-term multivitamin use and cancer endpoints have been inconsistent," researchers wrote in background information for the study, which appeared Oct. 17 on the website of the Journal of the American Medical Association.
"To date, large-scale randomized trials testing single or small numbers of higher-dose individual vitamins and minerals for cancer have generally found a lack of effect. Despite the lack of definitive trial data regarding the benefits of multivitamins in the prevention of chronic disease, including cancer, many men and women take them for precisely this reason."
J. Michael Gaziano, MD, MPH, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues analyzed data from the Physicians’ Health Study II, the only large-scale, randomized, double-blind, placebo-controlled trial testing the long-term effects of a common multivitamin in the prevention of chronic disease.
The trial included 14,641 male U.S. physicians ages 50 and 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 endpoints.
Analysis of the data indicated that men taking a multivitamin had a modest 8% 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 also was 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.
The researchers noted total cancer rates in their trial likely were influenced by the increased surveillance for prostate-specific antigen and subsequent diagnoses of prostate cancer during PHS II follow-up starting in the late 1990s.
"Approximately half of all confirmed cancers in PHS II were prostate cancer, of which the vast majority were earlier-stage, lower-grade prostate cancer with high survival rates," the researchers wrote. "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."
Although numerous individual vitamins and minerals contained in the PHS II multivitamin study have postulated chemopreventive roles, the authors wrote, it is difficult to definitively identify any single mechanism of effect through which individual or multiple components of their tested multivitamin may have reduced cancer risk.
"The reduction in total cancer risk in PHS II argues that the broader combination of low-dose vitamins and minerals contained in the PHS II multivitamin, rather than an emphasis on previously tested high-dose vitamins and mineral trials, may be paramount for cancer prevention," the authors wrote. "The role of a food-focused cancer prevention strategy such as targeted fruit and vegetable intake remains promising but unproven given the inconsistent epidemiologic evidence and lack of definitive trial data.
"Although the main reason to take multivitamins is to prevent nutritional deficiency, these data provide support for the potential use of multivitamin supplements in the prevention of cancer in middle-aged and older men."
The study is scheduled for presentation at the American Association for Cancer Research meeting, "Frontiers in Cancer Prevention Research," in Anaheim, Calif. The study is available at http://jama.jamanetwork.com/article.aspx?articleid=1380451.
"Observational studies of long-term multivitamin use and cancer endpoints have been inconsistent," researchers wrote in background information for the study, which appeared Oct. 17 on the website of the Journal of the American Medical Association.
"To date, large-scale randomized trials testing single or small numbers of higher-dose individual vitamins and minerals for cancer have generally found a lack of effect. Despite the lack of definitive trial data regarding the benefits of multivitamins in the prevention of chronic disease, including cancer, many men and women take them for precisely this reason."
J. Michael Gaziano, MD, MPH, of Brigham and Women’s Hospital and Harvard Medical School in Boston, and colleagues analyzed data from the Physicians’ Health Study II, the only large-scale, randomized, double-blind, placebo-controlled trial testing the long-term effects of a common multivitamin in the prevention of chronic disease.
The trial included 14,641 male U.S. physicians ages 50 and 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 endpoints.
Analysis of the data indicated that men taking a multivitamin had a modest 8% 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 also was 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.
The researchers noted total cancer rates in their trial likely were influenced by the increased surveillance for prostate-specific antigen and subsequent diagnoses of prostate cancer during PHS II follow-up starting in the late 1990s.
"Approximately half of all confirmed cancers in PHS II were prostate cancer, of which the vast majority were earlier-stage, lower-grade prostate cancer with high survival rates," the researchers wrote. "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."
Although numerous individual vitamins and minerals contained in the PHS II multivitamin study have postulated chemopreventive roles, the authors wrote, it is difficult to definitively identify any single mechanism of effect through which individual or multiple components of their tested multivitamin may have reduced cancer risk.
"The reduction in total cancer risk in PHS II argues that the broader combination of low-dose vitamins and minerals contained in the PHS II multivitamin, rather than an emphasis on previously tested high-dose vitamins and mineral trials, may be paramount for cancer prevention," the authors wrote. "The role of a food-focused cancer prevention strategy such as targeted fruit and vegetable intake remains promising but unproven given the inconsistent epidemiologic evidence and lack of definitive trial data.
"Although the main reason to take multivitamins is to prevent nutritional deficiency, these data provide support for the potential use of multivitamin supplements in the prevention of cancer in middle-aged and older men."
The study is scheduled for presentation at the American Association for Cancer Research meeting, "Frontiers in Cancer Prevention Research," in Anaheim, Calif. The study is available at http://jama.jamanetwork.com/article.aspx?articleid=1380451.
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