A research group from North Carolina investigated the effects of using estrogen-containing contraceptives on 25-Hydroxy Vitamin D levels and found that vitamin D levels were higher in those who used some form of estrogen supplementation.
Some studies have suggested that using estrogen in either hormone replacement therapy or contraception may increase the level of 25-Hydroxy Vitamin D [25(OH)D]. However, these trials examined small populations and did not take into consideration other factors that may affect 25(OH)D metabolism.
American researchers recently published an article in The Journal of Clinical Endocrinology & Metabolism investigating the association between the use of estrogen and 25(OH)D levels. 1696 African-American women between the ages of 23 and 34 years participated in the study. They brought all of their medications, contraceptives, and herbal and vitamin supplements to their visits, where these compounds were assessed and their blood 25(OH)D levels were measured. Time spent outside, vacations in sunny destinations, dietary vitamin D intake and alcohol consumption were also calculated, and BMI and melanin index (used to assess skin color) was measured. Researchers found that the overall concentration of 25(OH)D was lower than normal. 40% of participants used vitamin D supplements and vitamin D supplementation was determined by education, smoking, melanin and time spent outside. 25(OH)D levels were significantly higher among those who used estrogen, but they were more likely to use vitamin D supplements as well. However, 25(OH)D levels were also higher in those who used estrogen but did not take vitamin D supplements. Overall, estrogen supplementation increased 25(OH)D levels by 20%. Use of an estrogen-containing contraceptive had a bigger impact on 25(OH)D levels than low-dose vitamin D supplementation. Only the use of an intermediate- or high-dose of vitamin D supplement increased 25(OH)D levels more prominently than estrogen. Past estrogen use did not affect 25(OH)D levels.
It seems that estrogen supplementation and the level of 25(OH)D are associated. This is important in cases when women are planning to conceive and it may also help to identify women at risk of deficiency. Further studies are needed to identify the biological pathways that are responsible for the effect of estrogen (endogen or supplement) on vitamin D metabolism.
Written By: Dr. Fanni R. Eros