Multivitamin Use and Breast Cancer Incidence

Tue, 11 May 2010 11:35:00 +1200

A new study published in the American Journal of Clinical Nutrition this month has raised concerns that the use of multi-vitamin supplements may increase the risk of breast cancer. The study prospectively examined the association between multivitamin use and the incidence of invasive breast cancer in the Swedish Mammography Cohort.

In 1997, 35,329 cancer-free women completed a self-administered questionnaire that solicited information on multivitamin use as well as other breast cancer risk factors. Each participant contributed follow-up time from 1 January 1998 to the date of breast cancer diagnosis, death, or 31 December 2007, whichever came first.
The study observed a 19% increased risk of breast cancer associated with multivitamin use after adjustment for other breast cancer risk factors.

The questionnaire solicited information on multivitamin use, as well as some (but not all) breast cancer risk factors. During a mean follow-up of nine and a half years, 293 of the 9,000 women that claimed they took vitamins had developed breast cancer, leaving 8707 women or 96.7% who didnot develop the cancer. 681 of the 26,000 remaining non vitamin takers developed the cancer or 97.4% who did not develop the cancer.

Taken on face value this is a negative study on multivitamin use, however there are limitations to this research:

First, let's look at baseline characteristics of the participants. Multi-vitamin users had significantly greater incidence of benign breast disease, family history of breast cancer, use of oral contraceptives, and history of post-menopausal hormone use. These indices alone could have shifted the risk more toward this group.
They relied on patients' recall of multivitamin use, which is not usually very accurate. No information was given about the brands of supplements used, nor their nutrient content, quality, or other ingredients in them that might have some bearing on risk.
Also, calcium supplementation in this group conferred a 26% decreased risk of breast cancer. So, we don't know why the multivitamin group had an increased risk.

Experts Disagree with March 2010 Report

Officials from the American Council of Science and Health - a consumer education consortium with scientists and physicians on its Board - say that to associate a 19% increased risk of breast cancer with multivitamins by self-reporting over a 10-year period is absurd.

The American Institute for Cancer Research - an organization dedicated to cancer prevention - believes the study is not a reason to stop taking a daily multivitamin. To decrease the risk of cancer, the group advocates a diet rich in vegetables, fruits, whole grains, beans and low in red meat. However, they acknowledge that some women with nutritional deficiencies could benefit from a multivitamin. The UK's Health Food Manufacturers' Association states that ideally, vitamins and minerals should be obtained from diet, but surveys show that is just not very probable or possible. They make the point that the wisest decision is to eat both the best food and use the best multivitamin.

The Nurses' Health Study and Harvard's 2008 Study

Reported in the May 5, 1999 issue of the Journal of the American Medical Association, the Nurses' Health Study, involving 88,818 women, found that those who drank more than one alcoholic drink per day and took multivitamins gained a protective effect against breast cancer. Scientists note alcohol increases the risk of breast cancer, but folic acid and vitamin B6 - largely consumed in multivitamins - neutralize the risk. Note: Harvard Medical School states that women drinking more than one alcoholic drink per day should get at least 600 mcg of daily folic acid for the protective effect.

Reported in the March 15, 2008 online issue of the American Journal of Epidemiology, the Women's Health Study monitored close to 38,000 women for an average of 10 years, and found that there was no overall significant association between multivitamin-use and breast cancer risk. The researchers were generally associated with Harvard Medical School.

Utilize First-Rate Food and High-Potency Multivitamins

As Nutritional Medicine practitioners we are well aware that a sensible nutrition action-plan is to seize the best of both worlds: eat healthy and take a multivitamin. Obtain rich phytochemicals from food, and let a multivitamin fill in nutritional gaps. Numerous studies link multivitamin-use to heart health and a decrease in the risk of colon cancer; multivitamins are just too essential to give up. The study was not designed to establish cause and effect, and the researchers themselves agree that the findings do not prove that vitamins are to blame for incidence of breast cancer.

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Multivitamin Use and Breast Cancer Incidence