Unmasked correlation: Vitamin D and contraception exploration reveals new findings
Women using estrogen-based contraceptives may have higher levels of circulating vitamin D, according to a new study. The research, published in the Journal of Clinical Endocrinology & Metabolism, found that the use of oral contraceptives, patches, or rings containing estrogen was associated with a 20% increase in 25-hydroxy vitamin D levels.
Vitamin D is essential for maintaining the correct calcium and phosphorus levels in the blood and aids in the body's absorption of calcium, an essential component of bones. Foods high in vitamin D include fish and eggs, while around 90% of the vitamin is produced in the skin through a chemical reaction after exposure to sunlight.
The study, which included almost 1,700 African-American women living in and around Detroit, MI, aged 23-34, found that women who were using contraception containing estrogen tended to have higher vitamin D levels than other women. The increase remained significant even after controlling for confounding factors such as seasonal exposure to light.
Dr. Quaker E. Harmon, of the National Institutes of Health's National Institute of Environmental Health Sciences, said, "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."
During pregnancy, women produce increased levels of the active form of vitamin D to support the growth of the fetal skeleton. As a result, pregnant women have an increased risk of vitamin D deficiency and, therefore, a heightened risk of developing bone problems. Dr. Harmon advises that women who are planning to stop using birth control should ensure that their vitamin D levels are adequate while trying to conceive and during pregnancy.
The researchers could not find any behavioral differences such as increased time spent outdoors to explain the increase in vitamin D levels. Dr. Harmon said, "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 work is needed."
The study looked solely at African-American women, but Dr. Harmon said that the same association has been observed in young and older women who are not African-American. She added that she is continuing to follow this group of women to further investigate the relationship, as well as working on another group of participants to investigate how vitamin D varies across the menstrual cycle.
The researchers did not explore the potential implications during pregnancy, but the Enrichment Data suggests that adequate vitamin D levels during pregnancy are crucial for fetal skeletal development and may influence the risk of preeclampsia, gestational diabetes, and other complications. Since estrogen contributes to elevated vitamin D levels, the hormonal milieu during pregnancy, which naturally includes higher estrogen levels, could enhance vitamin D availability for both mother and fetus.
Furthermore, the estrogen-driven increase in vitamin D-binding protein could mean that pregnant women have higher total circulating vitamin D, which needs to be interpreted carefully because the free (bioavailable) vitamin D fraction may differ. This has implications for assessing vitamin D sufficiency in pregnant women.
Finally, the study's findings are important because vitamin D itself functions similarly to a hormone, playing critical roles beyond bone health, including muscle function and cardiovascular health. Estrogen’s support of vitamin D metabolism aligns with its role in maintaining skeletal integrity and hormonal balance in women.
- The study suggests that contraceptives containing estrogen may boost vitamin D levels, and these levels may decrease when women cease using contraception.
- Vitamin D is essential for bone health, aiding in the body's absorption of calcium, an essential component of bones.
- During pregnancy, women produce increased levels of the active form of vitamin D to support the growth of the fetal skeleton, increasing their risk of vitamin D deficiency.
- The researchers found that African-American women using contraception containing estrogen had higher vitamin D levels, and this association has been observed in women of various ethnicities.
- Adequate vitamin D levels during pregnancy are crucial for fetal skeletal development, influencing the risk of preeclampsia, gestational diabetes, and other complications.
- Estrogen's support of vitamin D metabolism aligns with its role in maintaining skeletal integrity and hormonal balance in women, extending beyond bone health to include muscle function and cardiovascular health.
