Nearly three-quarters of healthy premenopausal women experience at least one significant gastrointestinal symptom in the days before or during their period, according to a study. Abdominal pain and diarrhea are the most common complaints, but nausea and constipation also occur frequently.
The Science Behind Period-Related Gut Issues
Taylor Judkins, a nutrition researcher at the University of Florida who has studied the phenomenon for over a decade, explains that the discomfort often coincides: "If you ask women about 'period poops' they'll tell you they're having menstrual cramps and those GI cramps at the same time."
The mechanism begins with the uterus. As estrogen and progesterone levels fall sharply before menstruation, the body starts breaking down the uterine lining. Simultaneously, cells in the uterus produce hormone-like compounds called prostaglandins, which cause contractions in muscle cells throughout the uterus and digestive tract.
Judkins notes that the leading theory suggests some prostaglandins enter the bloodstream and stimulate similar contractions in the neighboring gut, explaining the intestinal cramping and diarrhea many experience, especially in the first day or two of their period.
Alternative Theories and Underlying Conditions
Another theory involves the vagus nerve, which connects the gut and brain and is sensitive to stress and inflammation. When activated, it triggers fluid release and increased gut contractions, leading to diarrhea. Judkins theorizes that menstruation may also activate this pathway.
Many women report constipation one to two weeks before their period, possibly due to high progesterone levels, though evidence on prevalence and timing is less clear. People with irritable bowel syndrome, inflammatory bowel disease, or endometriosis tend to have significantly worse symptoms around their periods, but period poops can occur without any underlying diagnosis.
"It's very common, and some will tell you that it's normal," Judkins says, "but it doesn't mean you should have to live with this drastic decrease in your quality of life."
What Can Help Reduce Symptoms?
Options exist, but none are a clear fix. Judkins and her team ran the only randomized trial to date testing probiotics for menstrual GI symptoms. Probiotics improved indigestion but not diarrhea, the symptom most people want to solve.
Some experts recommend oral contraceptives on a theoretical basis, as they reduce endometrial tissue and prostaglandin production. However, evidence for effectiveness on GI symptoms is lacking; one of Judkins' studies found that women on oral contraceptives still reported period poops.
Anti-inflammatory drugs like ibuprofen and naproxen reduce prostaglandin production, easing both uterine and digestive cramps. The catch: they can irritate the gut lining and cause diarrhea, and for those with Crohn's disease or ulcerative colitis, they can worsen symptoms and should generally be avoided.
For now, diet is the most practical starting point. Judkins recommends staying hydrated and eating more fiber—fruit, vegetables, whole grains, legumes—and less greasy comfort foods, which tend to worsen diarrhea. Exercise helps some people; the data aren't robust, but the risk is low. If symptoms are severe enough to affect work or daily life, that's worth raising with a doctor.
Why Isn't There a Solution Yet?
Judkins began studying period gut over a decade ago. "When you search these keywords, it's my name that comes up," she says. That's not a triumphant statement; it reflects a research culture that has treated menstrual health as a niche concern rather than an important issue affecting roughly half the population.
When researchers don't study something, clinicians are less likely to treat it. Patients are also less likely to raise it, because nobody has signaled that it's worth mentioning or that anything can be done. Judkins hopes that changes. "Funding for women's health research is ultimately a gain for everybody," she says.
