Do Vitamins Reduce Cancer Risk

A study showing a reduction of cancer in older physicians who take vitamins, well- it is a small, quite modest number. The study did not show a reduction in mortality. The study did not show a reduction in prostate cancer, the most common type of cancer found in these men. The study did not show a reduction in colon cancer. Nor did the study show a reduction in the risk of cancer mortality. People who had cancer before had a decrease risk of getting a second cancer, but those men that did not have a history of cancer before did not have a benefit from taking the vitamins. People who had a history of cancer in their family did not get a benefit from taking a vitamin (hard to beat genetics).

A more exciting study would have been dramatic reductions in cancers, increase in lifespan, and decrease in overall cancer mortality. Sadly, none of those were seen. It is not surprising that the news media got the numbers wrong. The LA Times mixed up percent of cancers with numbers of events in their story: saying 17%, but it was 17 events per 1000 person-years. Other papers talked about an 8% reduction of cancer- but that number is also incorrect. To put this into different terms, what this study showed is that of the major cancers effecting men, it has no effect on prostate cancer, no effect on colo-rectal cancer, and no effect on mortality (meaning, whether the participants got cancer or not, their age of death was not altered by taking a single multi-vitamin a day). To put their statistics another way, you would have to follow 83 older men for 11 years and possibly find that there is one less cancer in that group- but that cancer would have no effect on mortality.

cancer risk vitamins

Big Nutra is a multi-billion dollar industry, and many people believe that these supplements will ward off cancer – however, high doses of some supplements increase cancer risk.

Starting with the anti-oxidant supplements, it turns out that beta-carotene and vitamin E seem to increase mortality as well as higher doses of vitamin A. In fact when seventy-eight randomized trials with 296,707 people were looked at there was no effect of anti-oxidants on mortality. In 56 trials looked at antioxidants appeared to increase mortality (12.9% versus 10.6% –). This extended to vitamin E, beta-carotene, and vitamin A. Vitamin C had 9.9% mortality versus 9.3% in 29 trials and selenium had 6.7% versus 6.4%.  In addition, the increased doses of vitamin A were significantly associated with mortality.

The bottom line: the evidence that vitamins reduce cancer risk remains very minimal, and large doses of vitamins may actually increase risk of death. The more important lesson is this: these were all older men, in reasonable good shape, all physicians, few smokers, and with a balanced diet. If you wish to reduce your risk of cancer doing the following are hundreds of times more important to your health: stop smoking, eat more fiber, eat a balanced diet, use sun screen, and get some exercise.

There are two special classes of people for whom vitamins are necessary: pregnant women and people who have undergone some forms of weight loss surgery (RNY-gastric bypass, duodenal switch, bilio-pancreatic diversion, and variations of these).


Multivitamins in the Prevention of Cancer in Men:The Physicians’ Health Study II Randomized Controlled Trial
J. Michael Gaziano, MD, MPH; Howard D. Sesso, ScD, MPH; William G. Christen, ScD; Vadim Bubes, PhD; Joanne P. Smith, BA; Jean MacFadyen, BA; Miriam Schvartz, MD; JoAnn E. Manson, MD, DrPH; Robert J. Glynn, ScD; Julie E. Buring, ScD
JAMA. 2012;():1-10. doi:10.1001/jama.2012.14641.Published online October 17, 2012

Dietary supplements and cancer prevention: balancing potential benefits against proven harms.
Martínez ME, Jacobs ET, Baron JA, Marshall JR, Byers T.
J Natl Cancer Inst. 2012 May 16;104(10):732-9. Epub 2012 Apr 25.
PMID: 22534785 [PubMed – indexed for MEDLINE]

Antioxidant supplements for prevention of mortality in healthy participants and patients with various diseases.
Bjelakovic G, Nikolova D, Gluud LL, Simonetti RG, Gluud C.
Cochrane Database Syst Rev. 2012 Mar 14;3:CD007176. Review.
PMID: 22419320 [PubMed – indexed for MEDLINE]

Selenium and other antioxidants for chemoprevention of gastrointestinal cancers.
Jayaprakash V, Marshall JR.
Best Pract Res Clin Gastroenterol. 2011 Aug;25(4-5):507-18. Review.
PMID: 22122767 [PubMed – indexed for MEDLINE]

Dr. Terry Simpson About Dr. Terry Simpson
Dr. Terry Simpson received his undergraduate and graduate degrees from the University of Chicago where he spent several years in the Kovler Viral Oncology laboratories doing genetic engineering. He found he liked people more than petri dishes, and went to medical school. Dr. Simpson, a weight loss surgeon is an advocate of culinary medicine. The first surgeon to become certified in Culinary Medicine, he believes teaching people to improve their health through their food and in their kitchen. On the other side of the world, he has been a leading advocate of changing health care to make it more "relationship based," and his efforts awarded his team the Malcolm Baldrige award for healthcare in 2011 for the NUKA system of care in Alaska and in 2013 Dr Simpson won the National Indian Health Board Area Impact Award. A frequent contributor to media outlets discussing health related topics and advances in medicine, he is also a proud dad, husband, author, cook, and surgeon “in that order.” For media inquiries, please visit

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Latest Comments

  1. Lynn says:

    It still says private. I have seen a theory that multi-vitamins increase breast density in women and that some types of supplements may counteract anti-neoplastics or whatever chemotherapy drugs are called. I would wonder how such studies are done accurately since many people who take vitamins have other co-founding factors that influence their cancer risk. I have also read that the doses on pediatric vitamins are sometimes too high or too low and parents of kids who won’t eat properly rely on vitamins to cover the deficit. I think much of the prevention of cancer (and autism) has to do with the reduction of exposure to environmental toxins. I do, however, see lots of overweight people at the oncologists office so it could be that people with larger bodies don’t break down the toxins as well or that adipose stores excess estrogen. All the same, the advertising for vitamins and supplements are almost as convincing as the ads for wrinkle creams.

  2. thedoc says:

    Hopefully it is up now. There are some people for whom vitamins are very indicated: people who have had weight loss surgery- especially the malabsorptive types, and pregnant women. For chemotherapy patients it is probably important because if they are not eating enough it would hlep

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