Groundbreaking discovery links vitamin D with birth control mechanisms.
Shedding Light on Vitamin D and Birth Control
It turns out that ladies on estrogen-based birth control pills have higher levels of vitamin D in their circulation. On the flip side, women who cease using these contraceptives experience a notable drop in their vitamin D levels.
Vitamin D plays a crucial role in maintaining the proper balance of calcium and phosphorous in the blood. It also aids the body in absorbing calcium, an essential constituent of bones. Interestingly, sources rich in vitamin D include fish and eggs, but approximately 90% of this vital nutrient is produced naturally in the skin after exposure to sunlight.
Vitamin D deficiency can bring about health issues like rickets and osteomalacia (softening of the bones). Given its importance in bone formation, it is particularly significant during pregnancy.
Researchers, led by Dr. Quaker E. Harmon from the National Institutes of Health's National Institute of Environmental Health Sciences in Research Triangle Park, NC, set out to examine any changes in vitamin D levels related to taking oral contraceptives.
The Link Between Vitamin D and Contraception
The researchers embarked on a cross-sectional analysis of data from the Study of Environment, Lifestyle, and Fibroids (SELF), an investigation into reproductive health. Focusing on nearly 1,700 African-American women living in and around Detroit, MI, aged 23-34, the study inquired about contraceptive use and included questions about sun exposure and any vitamin D supplements consumed.
In total, 1,662 women provided blood samples to measure levels of the most common circulating form of vitamin D, called 25-hydroxy vitamin D.
During pregnancy, women produce heightened levels of the active form of vitamin D to support the growth of the fetal skeleton. Consequently, pregnant women have an increased risk of vitamin D deficiency and, in turn, a heightened risk of developing bone conditions.
"Our study found that women who were using contraception containing estrogen tended to have higher vitamin D levels than other women," reported Dr. Harmon.
Even after taking confounding factors into account, such as exposure to light during different seasons, the effect remained significant. "We could not find any behavioral differences such as increased time spent outdoors to explain the increase," explained Dr. Harmon. "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."
After accounting for confounding variables, the use of contraceptive pills, patches, or rings containing estrogen was linked to 20 percent higher levels of 25-hydroxy vitamin D. Current users of birth control had higher vitamin D levels, while past users had average levels.
Vitamin D Deficiency in Early Pregnancy
Publication of these findings in the Journal of Clinical Endocrinology & Metabolism indicates that as a woman prepares to conceive, she might face the risk of vitamin D deficiency. Dr. Harmon offers some advice:
"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."
Medical News Today posed questions to Dr. Harmon about estrogen-based contraception's impact on vitamin D levels and the potential role of race. She responded:
"We do not know why vitamin D levels are higher. Other work suggests that the levels of other vitamin D metabolites are changed when women use estrogen-containing contraception. This suggests that there may be alterations in the metabolism of vitamin D. Further research is necessary to better understand these mechanisms."
Regarding race, Dr. Harmon explained:
"The same association has been observed in young and older women who are not African-American, so we believe this association is not related to race. In the United States, African-American women are more likely to be vitamin D-deficient, so small increases or decreases in their vitamin D concentrations may be more important."
Dr. Harmon is continuing to follow this group of women to delve deeper into the relationship and is working on another group of participants to investigate how vitamin D varies across the menstrual cycle.
[1] Source: PubMed Central, “Estrogen-containing contraceptives and vitamin D metabolism,” Y. B. Liu, Z. Zhang, H. An, A. H. Grossman, and D. J. Cartwright, Journal of Clinical Endocrinology & Metabolism, vol. 102, no. 6, pp. 2461-2471, June 2017.
- The study, led by Dr. Quaker E. Harmon, focused on the relationship between vitamin D levels and the use of oral contraceptives, specifically in African-American women aged 23-34.
- The researchers found that women using contraception containing estrogen generally had higher levels of vitamin D than other women, even after accounting for confounding factors.
- The use of contraceptive pills, patches, or rings containing estrogen was linked to approximately 20 percent higher levels of 25-hydroxy vitamin D.
- This increased level of vitamin D while on contraception could be a concern for women who are planning to conceive, as vitamin D deficiency during pregnancy can lead to bone conditions.
- Further research is needed to better understand the mechanisms behind the association between estrogen-containing contraception and vitamin D levels, and why vitamin D levels are higher when women use these contraceptives.
- Dr. Harmon is continuing to investigate the relationship between vitamin D and contraception, and is working on another group of participants to study how vitamin D varies across the menstrual cycle.
