But we’re here to tell you these cyclical changes in your bowel movements that crop up just before or during your menstrual cycle are actually pretty common, thanks to shifting levels of hormones and hormone-like substances in the body. Fortunately, there are ways to make this unpleasant side effect less severe. Let us explain. These hormone-like molecules are released as the lining of your uterus breaks down before and during your menstrual cycle. Prostaglandins are what cause the muscles of the uterus to contract and push out the uterine lining during menstruation—but when there is an imbalance in prostaglandins, this can also cause the contraction of the muscles in your bowels, causing you to poop more and experience diarrhea, Brighten explains. (Prostaglandins are also responsible for period cramps.) Basically, your digestive tract is so relaxed that it doesn’t contract and push out waste as it normally would, leaving things to stagnate. While it doesn’t specifically address the prostaglandin aspect of period diarrhea and constipation, incorporating a high-quality probiotic supplement regularly can help support healthy digestion, says Shah.* A 2015 research review even found that some probiotic strains were able to lessen the duration of diarrhea symptoms3 by a day. For managing both diarrhea and constipation, fiber is also a must. “Aiming to eat at least 25 grams of fiber daily can support healthy bowel movements,” says Brighten. Soluble fiber (found in chia seeds, flaxseeds, oats, oat bran, barley, beans, lentils, psyllium, and most fruits—especially berries) can help combat diarrhea by bulking up stool; while insoluble fiber (found in fruit and vegetable skins, wheat, wheat bran, rye, and rice) may be particularly beneficial for alleviating constipation. If during your period your BMs are very painful (out of ordinary), you’re not able to keep food or drink down, or you develop vomiting, Shah says it’s important to see your doctor immediately. Editor’s Note: This article was originally published on March 28, 2019. A previous version of this article indicated that the hormone progesterone increases during your period. We have since clarified this statement to indicate that the hormone progesterone increases between ovulation and the time you get your period.
