Many people take multivitamins to gain some of the nutrients they might be lacking in their diets. Some also believe that multivitamins provide a type of insurance against certain types of health conditions, including cancer. Multivitamins are available over the counter as supplements, and most contain standard amounts necessary for daily intake. A few, however, provide mega-doses that may be more than the average person needs. Some diseases, such as breast cancer, have links to the use of multivitamins.
Increased Risk
A 2010 study in the "American Journal of Clinical Nutrition" showed that multivitamin use was a factor in increasing the risk for breast cancer. The study observed a 19 percent increase after making modifications for other risks for breast cancer, such as a history of breast disease, smoking or post-menopausal hormone use. Isolating a specific nutrient from this study was unsuccessful. The study could not identify specific brands of multivitamins that may have been the culprits in these situations, and concluded that the association between multivitamins and breast cancer still warrants further examination.
Folic Acid
Folic acid is a type of B vitamin essential for the synthesis of new cells in the body. Because it also helps prevent neural-tube defects in babies, pregnant women often take folic acid through prenatal vitamins. According to the Harvard School of Public Health, folic acid found in multivitamins may reduce the risk of some types of cancer, including breast cancer. However, high doses, such as mega-doses found specifically in vitamin supplements, may actually increase the risk of breast cancer. These types of supplements are not always from natural sources, but may instead be synthetically manufactured, which could promote the growth of cancerous cells.
Breast Density
A 2008 study in the "American Journal of Clinical Nutrition" researched multivitamin use among women, many of whom were taking the vitamins for better health and to reduce their chances of developing cancer. The study showed that multivitamin use was associated with an increase in breast density of 45 percent among pre-menopausal women. Increased breast density, often seen with a mammogram, can affect the amount of breast tissue as well as the number of breast cells that could turn into cancerous tissue. Increased breast density is associated with the formation of certain types of cancer, including carcinoma in situ, a type of cancer that often remains where it starts in either the ducts or the lobules of the breast.
Things to Consider
Multivitamins can be helpful as supplements if you do not get enough nutrients through your diet. Talk with your doctor if you are concerned about the possible connection between multivitamins and breast cancer to determine how much of each nutrient you should be getting every day. Avoid taking multivitamins that promise mega-doses of certain types of nutrients, as these may be more than you need.
References
- Harvard School of Public Health: Vitamins: The Bottom Line
- "American Journal of Clinical Nutrition"; Multivitamin Use and Breast Cancer Incidence in a Prospective Cohort of Swedish Women; Susanna C. Larsson, et al.; 2010
- "American Journal of Clinical Nutrition"; Multivitamin-Multimineral Supplement Use and Mammographic Breast Density; Sylvie Bérubé, et al.; May 2008
- Women's Health.gov; Folic Acid Frequently Asked Questions; May 2010
- American Cancer Society; Breast Cancer; February 2011
