A longtime reader of the blog pointed me to this. It’s blowing my mind. From JAMA, “Multivitamins in the Prevention of Cancer in Men The Physicians’ Health Study II Randomized Controlled Trial“:
Context Multivitamin preparations are the most common dietary supplement, taken by at least one-third of all US adults. Observational studies have not provided evidence regarding associations of multivitamin use with total and site-specific cancer incidence or mortality.
Objective To determine whether long-term multivitamin supplementation decreases the risk of total and site-specific cancer events among men.
Design, Setting, and Participants A large-scale, randomized, double-blind, placebo-controlled trial (Physicians’ Health Study II) of 14 641 male US physicians initially aged 50 years or older (mean [SD] age, 64.3 [9.2] years), including 1312 men with a history of cancer at randomization, enrolled in a common multivitamin study that began in 1997 with treatment and follow-up through June 1, 2011.
Intervention Daily multivitamin or placebo.
Main Outcome Measures Total cancer (excluding nonmelanoma skin cancer), with prostate, colorectal, and other site-specific cancers among the secondary end points.
Here’s the gist. They rounded up more than 14,000 doctors 50 years or older in 1997 and randomized them to get a daily multivitamin or placebo, and then they followed them through June of 2011. Otherwise, they did nothing to these participants, so there’s every reason to believe they were otherwise treated similarly. They wanted to see if the two groups developed cancer at different rates. They did.
Men who took a daily multivitamin had a statistically significant lower rate of cancer than those who took the placebo (17.0 versus 18.3 events per 1000 person-years). Although mortality was lower as well, it wasn’t statistically significant (4.9 versus 5.6 events per 1000 person-year).
This was an extremely large study, well done, with amazing follow-up. You can’t dismiss it easily.
Multivitamins are cheap. You can buy them by the barrel at Costco. There are few harms or side effects. And, unlike many of the things I often roll my eyes at, they appear to really reduce the risk of cancer. Plus, you get the nutritional benefits. I’ve been lazy about taking one for a while, but I think I may reconsider.