Written by Marcia J. Egles, MD. Studies have suggested that low vitamin D intake may increase breast cancer risk.
A Canadian study has reported a reduced risk of breast cancer among women using vitamin D supplements (1). Although the past data has not been conclusive, several other studies have suggested that low vitamin D intake may increase breast cancer risk (2,3,4). This case-control dietary study, performed at a northern latitude (43 degrees north) with relatively low vitamin D from sun exposure, found that those who took more than 400 international units per day of vitamin D supplements had lower odds of breast cancer than those who took no supplements. No associations of reduced risk were determined for vitamin D and calcium intakes from food, or from calcium supplements alone.
The study examined 3,101 cases of breast cancer identified through the Ontario Cancer Registry for women aged 25-75 (diagnosed 2002-2003). Controls were recruited by randomly dialed telephone requests for women without cancer histories. Over 25,000 Ontario households were phoned in order to obtain the 3,471 case-matched controls willing to participate in the study. Ninety per cent of the participants were of white ethnicity. The average age was 56 years. Thirty-two per cent of the cases and thirty-six per cent of the controls were pre-menopausal.
Questionnaires concerning lifestyle, diet and medical history were mailed to all of the women in the study. They were completed by 75 per cent of the cases and 80 per cent of the controls, yielding a large survey population and a myriad of data. Particular attention in the study was focused on calcium and vitamin D intakes. Vitamin D supplement usage was reported by 13 per cent of the cases and 14 per cent of the controls.
Significant among the findings was an adjusted odds ratio of 0.76, (95 % confidence interval 0.59, 0.98) for breast cancer for those with vitamin D supplement intakes of more than 400 IU per day, compared to those who took no supplements. (An odds ratio is the ratio of the odds of an event occurring in one group to the odds of it occurring in another group. A 0.76% odds ratio represents 76% as much risk, or a 24% odds reduction risk.) Although pre-menopausal women were included in the study, unfortunately there were statistically insufficient numbers of them taking vitamin D supplements to generate complete findings for subgroups. (The reported 0.76 odds ratio represents the entire populations of pre- and postmenopausal women in the study.)
The researchers emphasized the need for continued clinical trials addressing vitamin D and breast cancer. Although their study could not access early-life vitamin D intake, they hypothesized that vitamin D exposure during adolescence may be most important to breast cancer prevention.
Source: Anderson, Laura N., et al. “Vitamin D and calcium intakes and breast cancer risk in pre-and postmenopausal women.” The American journal of clinical nutrition (2010): ajcn-28869.
© 2010 by the American Society for Nutrition
Posted June 18, 2010
References:
- Laura N. Anderson et al, Vitamin D and calcium intakes and breast cancer risk in pre- and
postmenopausal women,Am J Clin Nutr doi: 10.3945/ajcn.2009.28869. - Cui Y, Rohan TE. Vitamin D, calcium, and breast cancer risk: a review. Cancer Epidemiol Biomarkers Prev 2006;15:1427–37.
- Perez-Lopez FR, Chedraui P, Haya J. Review article: vitamin D acquisition and breast cancer risk. Reprod Sci 2009;16:7–19.
- Rohan T. Epidemiological studies of vitamin D and breast cancer. NutrRev 2007;65:S80–3.
