Vitamin D Levels Fall When Estrogen-Containing Birth Control Pills Stopped Interview with:

Quaker Harmon M.D., Ph.D. Epidemiology Branch National Institute of Environmental Health Sciences Research Triangle Park, NC 27709

Dr. Quaker Harmon

Quaker Harmon M.D., Ph.D.
Epidemiology Branch
National Institute of Environmental Health Sciences
Research Triangle Park, NC 27709 What is the background for this study? What are the main findings?

Response: Vitamin D is important for bone health. In the United States many women are vitamin D deficient. Vitamin D does not naturally occur in many foods, however some foods are fortified with vitamin D. Supplements and sunshine are the most reliable sources of vitamin D.
Previous studies suggested that women using birth control pills containing estrogen had higher levels of vitamin D. These studies were generally small and were not always able to examine important factors such as time spent outside. We were interested in examining the association between hormonal contraception and vitamin D levels in a larger group of women.

We found that women who use estrogen-containing contraception had a 20% increase in their vitamin D levels. This increase was not due to time spent outside or behaviors related to choice of contraception. The magnitude of increase for hormonal contraception was smaller than for regular use of a supplement containing vitamin D. What should readers take away from your report?

Response: Regular use of supplements containing vitamin D is the most reliable way to increase vitamin D levels. Vitamin D levels are likely to fall when women stop using estrogen-containing contraception. Women who are stopping their birth control to start planning a pregnancy should work with their health care provider to ensure that their vitamin D levels remain adequate while trying to conceive and during pregnancy. What recommendations do you have for future research as a result of this study?

Response: Further research is needed to identify the mechanisms through which estrogen-containing contraception influences vitamin D levels. Other research suggests that many vitamin D metabolites may be influenced by supplemental estrogen. We also don’t know how quickly vitamin D levels fall following the discontinuation of hormonal contraception. We are continuing to follow the vitamin D levels in this group of women to track changes over time. We are also working with women from another study to examine changes in vitamin D across the menstrual cycle. Thank you for your contribution to the community.


Use of Estrogen-Containing Contraception Is Associated With Increased Concentrations of 25-Hydroxy Vitamin D
Quaker E. Harmon, David M. Umbach, and Donna D. Baird
JCEM First Published Online: August 04, 2016


Note: Content is Not intended as medical advice. Please consult your health care provider regarding your specific medical condition and questions.

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Last Updated on August 8, 2016 by Marie Benz MD FAAD