Cancer Causes Control 21(3):479 (2010)
Julia A Knight, Jody Wong, Kristina M Blackmore, Janet M Raboud and Reinhold Vieth
Prosserman Centre for Health Research, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, 60 Murray Street, Room 5-237, Box 18, Toronto, ON, M5T 3L9, Canada, knight at lunenfeld.ca.
Objective Vitamin D may reduce breast cancer risk through an effect on steroid hormones in cycling women. We conducted a study to determine whether there is an association between circulating 25-hydroxyvitamin D (25(OH)D) and estradiol and progesterone in young women.
Methods Volunteer women aged 18–22 and not using hormonal contraceptives were recruited during summer and winter. They provided demographic and lifestyle information and a blood sample. Women recruited in winter gave a second sample after taking vitamin D supplement for 4 weeks. There were 101 women sampled during the luteal phase (1–14 days prior to the start of the next menstrual period). Generalized estimating equation linear regression models were used to examine the relationship between 25(OH)D and estradiol and progesterone.
Results Per increase of 10 nmol/l of 25(OH)D, progesterone multiplicatively decreased by a factor of 10% (95% CI 5–14%, p < 0.001) and estradiol decreased by a factor of 3% (95% CI 0–6%, p = 0.04) after adjustment for age, body mass index, ethnicity, season, alcohol use, smoking, and physical activity.
Conclusions Higher levels of vitamin D may reduce progesterone and estradiol, providing a potential mechanism for reduction in breast cancer risk from increased vitamin D exposure in young women. DOI: 10.1007/s10552-009-9466-0 PMID: 19916051