Estrogen-Based Birth Control Seems to Boost Vitamin D

Contraceptive pills box with gender symbol on pink background
Contraceptive pills box with gender symbol on pink background

An interesting bit of research has come out recently that looks at how contraceptives that contain estrogen may influence a woman’s vitamin D levels. The study is interesting for two reasons. The first is that it’s a neat look at some of the body’s underlying mechanics, and the second is that there are some weird acrobatics going on with how the press release is describing the findings.

Vitamin D is known for its role in managing the immune system and calcium absorption in the blood. Most vitamin D comes from sunlight with only a small portion (~10%) coming from food. During pregnancy, women produce more vitamin D in order to support the development of the child’s skeleton, which is why they are at higher risk of deficiency.

In women who use estrogen-based contraceptives, something similar happens except, without actually being pregnant, vitamin D levels would rise. The study looked at 1,662 African-American women between ages 23 and 34 and found that those who currently use estrogen-containing contraceptives had around a 20% higher level of vitamin D. Those who only used estrogen contraceptives in the past had normal levels.

Where things get a bit odd is when the press release comes into play. For whatever reason, the Endocrine Society is emphasizing the idea that a woman’s vitamin D levels may drop when they stop using birth control. As an extension of this, women are also urged to take steps to avoid vitamin deficiencies when they stop contraception.

This is weird because the study’s findings don’t directly support that kind of cautioning. Nothing in the findings suggests that women who stop using contraception are at risk of having below-average vitamin D and it’s not clear if the structure of the study is even capable of finding that out. Although the logic behind the press release is sound and the advice is valid-if-generic, it seems more like someone was trying to add spin to a rather standard piece of research.

“Vitamin D Levels May Drop When Women Stop Using Birth Control,” Endocrine Society web site, August 4, 2016;, last accessed August 8/16.

Harmon, Q., “Use of Estrogen-Containing Contraception is Associated With Increased Concentrations of 25-Hydroxy Vitamin D,” JCEM, 2016;