Explained: The Weird Reason You Always Get Diarrhea During Your Period

Contributing Health & Nutrition Editor By Stephanie Eckelkamp
Contributing Health & Nutrition Editor
Stephanie Eckelkamp is a writer and editor who has been working for leading health publications for the past 10 years. She received her B.S. in journalism from Syracuse University with a minor in nutrition.
Medical review by Wendie Trubow, M.D., MBA
Functional Medicine Gynecologist
Wendie Trubow is a functional medicine gynecologist with almost 10 years of training in the field. She received her M.D. from Tufts University.
The Period Side Effect No One Talks About But Should, Explained

Image by Audrey Shtecinjo / Stocksy

Ladies, tell me if this sounds familiar: You're humming along just fine all month with perfectly average BMs and then—BAM! Things suddenly become...explosive. You know you know what I'm talking about. Unfortunately, the topic of period diarrhea isn't quite as easy to commiserate over as cramps and mood swings, so no one really addresses it.

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.

How shifting hormones mess with your poop.

"Period diarrhea is often caused by elevated prostaglandins," says Jolene Brighten, N.D., functional naturopathic medicine doctor and mbg Collective member. 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.)

Some women, on the other hand, may experience constipation. Between ovulation and the time you get your period, there's an increase in the hormone progesterone, which relaxes the muscles of your digestive tract. If levels of progesterone are elevated, then bloating, gas, and constipation can result, explains Brighten. Basically, your digestive tract is so relaxed that it doesn't contract and push out waste as it normally would, leaving things to stagnate.

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How to prevent period diarrhea or constipation.

The good news: You're not totally at the mercy of your hormones. Focusing on the right foods and specific nutrients can help get your bathroom habits back on track.

Because prostaglandins are synthesized from omega fatty acids, shifting your diet to contain more omega-3 fatty acids (from fatty fish like salmon and sardines, flaxseeds, chia seeds, hemp seeds, walnuts, or an omega-3 supplement) and fewer omega-6 fatty acids (found in vegetable oils and many processed foods) can lessen their effect and help prevent diarrhea, says Brighten.

Magnesium, an essential mineral needed to complete more than 300 biochemical reactions in the body, can help as well. "Consider adding a magnesium supplement to support healthy prostaglandins and hormones," says Brighten. "Magnesium citrate can help with constipation, but avoid this form of magnesium if diarrhea is your issue."

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.

Of course, if these steps don't help, and you're having significant digestive distress at other times of the month as well, be sure to talk to your doc to rule out a more serious condition like irritable bowel syndrome (IBS).

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