A new study has found that women on estrogen-containing forms of birth control have higher levels of vitamin D than other women and that their vitamin D levels are likely to drop if they stop taking birth control.
The study involved data from almost 1,700 African-American women between the ages of 23 and 34, all of whom lived in or near Detroit. Participants completed a survey about their birth control use, vitamin D supplement use, and the amount of time they spent outside. Even after controlling for behavioral differences (e.g. time spent outdoors), the women who used estrogen-containing contraceptives had higher average levels of vitamin D.
There are many hormonal birth control drugs on the market, including pills like Minastrin 24 FE and vaginal rings like Nuvaring. The pill is the most widely used method, with four out of five sexually active women reporting that they have used an oral contraceptive.
Both pills and other hormonal birth control methods, such as NuvaRing, have been linked to lower Vitamin D after stopping the dosages.
Why is Vitamin D Important?
Vitamin D is a hormone that helps the body absorb calcium. As anyone who has ever seen a “Got Milk?” ad knows, calcium is necessary to keep bones strong. By assisting with calcium absorption and blocking the action of parathyroid hormone (a hormone that reabsorbs bone tissue), vitamin D helps prevent bones from becoming brittle and weak.
During pregnancy, vitamin D is especially important, as it is needed to support the development of the fetal skeleton.
The human body produces vitamin D naturally when skin is exposed to sunlight. While sun exposure is our main route to increasing vitamin D, about 10% of vitamin D comes from foods such as fish, milk, yogurt, and egg yolks.
Implications of the Study
Before getting into the implications of the new study on birth control and vitamin D levels, it’s worth noting some of the study’s limitations. Previous research has shown that dark skin absorbs less sunlight, and that darker-skinned people get less vitamin D from sunlight than their lighter-skinned counterparts. Furthermore, people who live in the northern U.S. get less vitamin D from sun exposure than people living in the southern U.S. simply because they don’t get as many sunny days. The recent study only used data from women who identify as African-American and live in Detroit, and future research with a diverse population is needed to test the hypothesis that quitting birth control causes a side effect of decreased vitamin D levels.
If the results of this study do bear out, women who plan to quit taking birth control to become pregnant need to make an extra effort to maintain adequate vitamin D levels. Women who are planning a pregnancy should talk with their doctor to determine whether they need to make dietary changes or take vitamin D supplements after stopping their hormonal birth control.