Recent studies of vitamin supplementation effects on breast cancer development have conflicting results.
A Swedish study published in the March 24, 2010 online issue of The American Journal of Clinical Nutrition found that use of multivitamins is associated with an increased risk of breast cancer.
This study followed over 35,000 women aged 49-83 who in 1997 were cancer free and answered a questionnaire regarding usage of multivitamins and other breast cancer risk factors. Ten years later, after taking into consideration other factors such as weight, exercise and nutritional habits, researchers found that women taking multivitamins were 19% more likely to develop breast cancer. 293 of 9,017 women taking multivitamins in the study developed breast cancer, compared to 681 cases in 26,000 women not taking the supplements.
“These results suggest that multivitamin use is associated with an increased risk of breast cancer. This observed association is of concern and merits further investigation,” said Swedish researchers in their conclusion.
A separate study presented to the American Association for Cancer Research 101st Annual Meeting 2010 found that multivitamins and calcium supplements reduced the risk of breast cancer.
In this study, researchers compared vitamin and calcium intakes of 268 women with breast cancer and 457 women without breast cancer, all in Puerto Rico. Study authors concluded that taking a multivitamin tablet reduced breast cancer risk by about 30% and a calcium supplement reduced risk by 40%.
Researchers also studied the ability of the women’s DNA to self-repair knowing the link between DNA’s ability to repair and several types of cancer including breast cancer, HealthDay News reported.
“The effect was seen with multivitamins, not with single vitamins," study co-author Dr. Jaime Matta, a professor at Ponce School of Medicine in Ponce, Puerto Rico told HealthDay News. "It’s possible that the vitamins work better together than individually."
"We found that taking multivitamins and calcium supplements were strongly protective against breast cancer," Dr. Manuel Bayona of the Ponce School of Medicine said according to HealthDay News. Dietary supplements do not need the approval of the U.S. Food and Drug Administration (FDA). Under the Dietary Supplement Health and Education Act of 1994 (DSHEA), the manufacturer is responsible ensuring that a dietary supplement is safe before it is marketed and the FDA only takes action against any unsafe dietary supplement product after it reaches the market.