Recent research has been questioning the popular belief that multivitamin and mineral supplements can help prevent cancer and other chronic diseases.

Studies evaluating the effects of multivitamin and mineral supplements on cancer risk have largely been observational, with considerable limitations and conflicting results.

Researchers reviewed evidence that assessed the effects of supplements containing individual vitamins, a combination of a few select vitamins, or complete multivitamin and mineral supplements, with a focus on the recent Physicians’ Health Study II (PHS II). PHS II is a landmark trial that followed generally healthy middle-aged and older men (mean age 64 years) who were randomized to daily MVM supplementation for a mean duration of 11 years.

  • Men taking multivitamin and mineral supplements experienced a statistically significant 8% reduction in incidence of total cancer.
  • Men with a history of cancer derived an even greater benefit: cancer incidence was 27% lower with multivitamin and mineral supplements  versus placebo.

 Positive results of the Physicians’ Health Study II contrast with randomized studies of individual vitamins or small combinations of vitamins, which have largely shown a neutral effect, and in some cases, an adverse effect, on cancer risk.

The results of Physicians’ Health Study II  may have a considerable public health impact, potentially translating to prevention of approximately 68 000 cancers per year if all men were to use similar supplements, and to an even greater benefit with regard to secondary prevention of cancer.1

Vitamins and cancer prevention

In recent years there has been many studies that say multivitamins can help protect against certain cancers and equally, as soon as a positive study comes out, a study comes out to debunk the use of multi-vitamins. Recently a very important study published in the Journal of the American Medical Association (JAMA) concluded that daily multivitamin supplementation “modestly but significantly reduced the risk of total cancer.”

Here is the summary of the research:

“In this large-scale randomized trial of 14,641 middle-aged and older men, a daily multivitamin supplement significantly but modestly reduced the risk of total cancer during a mean of 11 years of treatment and follow-up. 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.”

Here is the study background:

“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. (This study’s objective is) to determine whether long-term multivitamin supplementation decreases the risk of total and site-specific cancer events among men.”

What makes this study significant is that it was a “large-scale, randomized, double-blind, placebo-controlled trial.” In addition it followed 14,641 men initially aged 50 years or older 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.

During the average 11 year follow up 2,669 men developed confirmed cancer, including 1373 cases of prostate cancer and 210 cases of colorectal cancer. Compared with placebo, men taking a daily multivitamin had a statistically significant reduction in the incidence of total cancer.

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1. Hardy ML, Duvall K. Multivitamin/multimineral supplements for cancer prevention: implications for primary care practice. Postgrad Med. 2015 Jan;127(1):107-16. doi: 10.1080/00325481.2015.993284.

2. Gaziano JM, Sesso HD, Christen WG, et al. The Physicians’ Health Study II Randomized Controlled Trial. JAMA. 2012;:1-10. doi:10.1001/jama.2012.14641