Research Triangle Park, NC—When women terminate use of birth control pills or other contraceptives containing estrogen, they risk having falling vitamin D levels, which can be especially detrimental if they are trying to get pregnant, new research suggests.
During pregnancy, increased amounts of the active form of vitamin D are created to support formation of the fetal skeleton, raising the risk of a deficiency in the mother, according to the article appearing in the Journal of Clinical Endocrinology & Metabolism.
“Our study found that women who were using contraception containing estrogen tended to have higher vitamin D levels than other women,” said the study's first author, Quaker E. Harmon, MD, PhD, of the National Institutes of Health's (NIH's) National Institute of Environmental Health Sciences in Research Triangle Park, N.C. “We could not find any behavioral differences, such as increased time spent outdoors to explain the increase. Our findings suggest that contraceptives containing estrogen tend to boost vitamin D levels, and those levels are likely to fall when women cease using contraception.”
Data from the Study of Environment, Lifestyle & Fibroids (SELF), a study of reproductive health and uterine fibroids in nearly 1,700 African-American women between the ages of 23 and 34 in the Detroit area, was used for the cross-sectional analysis. For that study, participants answered questions about contraceptive use, the amount of time they spent outdoors and any vitamin D supplements they took.
In addition, the women provided blood samples, which were analyzed to measure levels of 25-hydroxy vitamin D, the primary circulating form of vitamin D.
After adjustment for seasonal exposure to sunlight, researchers found the use of contraceptive pills, patch or ring containing estrogen was associated with a 20% higher 25-hydroxy vitamin D level.
Results also indicate that, while current birth control users tended to have higher levels of vitamin D in the blood, past contraceptive users had average levels of Vitamin D.
“The increase in 25(OH)D with use of estrogen-containing contraceptives raise mechanistic questions regarding the biological pathways involved, and highlights the need for studies that examine possible endogenous estrogen effects on vitamin D,” study authors conclude.
“Our findings indicate women may run the risk of developing vitamin D deficiency just when they want to become pregnant,” Harmon explained in a press release from The Endocrine Society. “For women who are planning to stop using birth control, it is worth taking steps to ensure that vitamin D levels are adequate while trying to conceive and during pregnancy.”
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