Many adults take multivitamins in hopes that they will help them meet their nutritional needs. Most multivitamins contain a combination of essential vitamins and minerals in different amounts of each depending on the brand. They are generally taken on a daily basis and may be prescribed by a doctor or done strictly by patient choice. These vitamins are usually taken in hopes that they will help prevent illness or disease, such as cancer. Unfortunately, most observational studies have not shown a consistent benefit with taking vitamins and cancer prevention. Also, studies looking at individual vitamins and minerals have generally found little or no benefit for cancer prevention.
Researchers wanted to better clarify the role of multivitamins for cancer prevention by performing a randomized trial. A study, called the Physicians' Health Study II, was performed to look for a potential relation between daily multivitamins and health outcomes. The study found that men who took a daily multivitamin had a lower risk of cancer.
The Physician's Health Study II was a large trial that was started in 1997 and followed participants through 2011. The randomized trial included 14,641 male physicians aged 50 years or older. The physicians were assigned to either a daily multivitamin or placebo. Participants were followed over the course of the trial for development of any cancer and specifically nonmelanoma skin cancer, prostate cancer, and colorectal cancer. About 67% of the men were still taking the pill by the end of the trial.
After about 11.2 years, new cancer developed in 18.2%. Men who took the multivitamin had a significantly lower rate of any type of cancer and compared to those that took placebo. Rates of cancer related deaths were lower in men taking the multivitamin, but the difference was not quite statistically significant. There was no difference when looking specifically at colorectal cancer, prostate cancer, or other specific cancers.
A randomized trial is one of the most dependable types of research. It can be used to demonstrate cause and effect. This trial is also considered more reliable because it has such a large number of participants. The study also followed participants over a long period of time which is important when looking at the development of cancer. A downside to this study was that only about two thirds of the men were still taking the pill they were supposed to take by the end of the study. Also, the fact that this study used a multivitamin with many different ingredients makes it difficult to know which element or combination of elements may have been most useful.
According to this study, it does appear that taking a multivitamin may help reduce the risk of cancer in men. However, this does not necessarily mean that every man should be taking a multivitamin. With certain vitamins, there can be too much of a "good" thing and high doses can be harmful. The decision to start taking a multivitamin should be made with your doctor. Also, you should consider another even more beneficial option to getting your daily dose of vitamins and minerals. That is eating healthy food including plenty of fruits and vegetables.
Gaziano JM, Sesso H, et al. Physicians' Health Study II trial. JAMA 2012 Nov 14;308(18):1871.
Last reviewed January 2013 by Brian Randall, MD
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