The authors carried out a randomized trial involving 15,000 male doctors. They found that those taking multivitamins over the long-term had a statistically significant, albeit modest reduction in cancer incidence after being tracked for ten years.
As background information, the researchers explained:
"Multivitamins are the most common dietary supplement, regularly taken by at least one-third of U.S. adults. The traditional role of a daily multivitamin is to prevent nutritional deficiency. The combination of essential vitamins and minerals contained in multivitamins may mirror healthier dietary patterns such as fruit and vegetable intake, which have been modestly and inversely associated with cancer risk in some, but not all, epidemiologic studies.
Observational studies of long-term multivitamin use and cancer end points have been inconsistent. 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."
Previous studies have provided conflicting resultsAs the authors mentioned, dozens of studies over the last few years on multivitamins and their benefits have had mixed results.
A study published in Archives of Internal Medicine in February 9th, 2009, reported that long-term multivitamin intake by postmenopausal women made no difference to developing common cancers, cardiovascular disease, or risk of premature death for any reason.
The JAMA study released on Wednesday suggests that a daily multivitamin could lower the risk of developing cancer for middle-aged and older men.
Several reports agree that prenatal multivitamin supplements lower the risk of giving birth to a low risk baby compared to iron-folic acid supplementation.
Scientists from the University of Minnesota School of Public Health reported in the Journal of the American Dietetic Association in 2006 that teenagers who take daily multivitamin supplements tend to have a healthier diet and lifestyle than those who do not. This tendency could make it hard to determine what impact multivitamins over the long term might have on young people.
The Physicians' Health Study IIJ. Michael Gaziano, M.D., M.P.H., and team looked at data from PHS II (the Physicians' Health Study II). He says it is the only large-scale randomized, double-blind, placebo-controlled trial to test what the long-term effects of a common multivitamin is on chronic disease prevention.
The human study involved 14,641 male doctors, all American, who were aged at least fifty years at baseline. 1,312 of them had a history of cancer at randomization. The multivitamin study started in 1997. Treatment and follow-up continued until June 1st, 2011.
The participants were randomly selected into one of two groups:
- The multivitamin group - they received a daily multivitamin
- The placebo group - they received a daily placebo that looked and tasted just like the multivitamin
They were all followed for 11.2 years (average).
Below are some data gathered during the multivitamin treatment period:
- There were 2,669 confirmed cases of cancer, including..
- 1,373 prostate cancers
- 210 colorectal cancers
- several cases of men experienced multiple events
- 2,757 (18.8%) of the men died for any reason
- 859 (5.9%) of the men died from cancer
- Those taking multivitamins had an 8% lower risk of developing cancer compared to those on placebos
- Those in the multivitamin group had an 8% lower risk of developing epithelial cell cancer
- About half of all cancers were of the prostate, the majority in early stage
- Multivitamin use over the long term made no difference to prostate cancer risk
- Cancer mortality did not appear to be affected by multivitamin use
- Of the 1,312 who had a history of cancer at baseline, those on multivitamins had a similar reduction on subsequent cancer risk
Increased surveillance may have influenced the resultsTotal cancer rates may have been influenced by higher-than-normal surveillance for PSA (prostate-specific antigen) among the participants in the late 1990s.
The authors wrote:
"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 significant reduction in total cancer minus prostate cancer suggests that daily multivitamin use may have a greater benefit on more clinically relevant cancer diagnoses."
The researchers say it is hard to pinpoint which vitamin(s) or mineral(s) in this study were the main contributors towards cancer protection.
"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 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."
What are multivitamin supplements? Why do people take them?The main reason people take multivitamins is either to ensure better overall health or prevent nutritional deficiency. The authors believe that their findings provide evidence supporting the taking of multivitamins in middle age for cancer prevention (if you are male).
Basic commercial multivitamin supplements typically contain the following ingredients:
- Vitamins: C, B1, B2, B3, B5 (pantothenate), B6, folic acid (B9), B12, H (biotin), A, E, D3, K1
- potassium iodide
- cupric (sulfate anhydrous, picolinate, sulfate monohydrate, trioxide)
Written by Christian Nordqvist