The experience of having more frequent or looser bowel movements at the start of menstruation is often referred to as “period poop.” This change in digestive function is a normal response to the dramatic hormonal shifts that characterize the menstrual cycle. The body’s reproductive and gastrointestinal systems are intimately connected, sharing a sensitivity to the same chemical messengers. Studies show that a significant majority of menstruating individuals (around 73%) report experiencing gastrointestinal symptoms, such as abdominal pain or diarrhea, just before or during their period.
The Mechanism of Prostaglandins
The primary biological reason for the sudden increase in bowel activity is a group of hormone-like lipids called prostaglandins. These compounds are produced by the lining of the uterus as it prepares to shed each month. Their main function is to initiate the muscular contractions necessary to expel the endometrial tissue during the menstrual phase.
Because the uterus is anatomically close to the intestines and colon, the high concentration of prostaglandins released locally can affect these neighboring organs. This “spillover effect” means the chemicals that cause uterine cramping also stimulate the muscles of the bowels. This increases gastrointestinal motility, causing digested food to move through the colon faster than usual, leading to more frequent, softer stools or diarrhea.
Prostaglandins also reduce the efficiency with which the colon absorbs water from waste material. This decreased water absorption contributes directly to the softer consistency of the stool. The muscular contractions in the intestines, combined with the faster transit time, cause the cramping sensation often experienced alongside uterine cramps.
How Other Hormones Influence Digestion
The shift in bowel habits is also influenced by the withdrawal of another reproductive hormone, progesterone. Progesterone levels rise significantly during the luteal phase (the time between ovulation and menstruation) and function as a smooth muscle relaxant throughout the body, including the gastrointestinal tract.
The relaxing effect of elevated progesterone slows down gut motility, which often causes constipation or bloating in the days leading up to the period. When fertilization does not occur, progesterone and estrogen levels drop sharply. The sudden removal of progesterone’s braking effect means that gut motility speeds up rapidly.
This quick acceleration, coupled with high levels of prostaglandins, creates the hormonal combination for rapid and urgent bowel movements. The digestive system shifts quickly from a state of pre-menstrual slowdown to a state of menstrual acceleration.
Managing Increased Bowel Activity
While these digestive changes are a normal part of the menstrual cycle, strategies can help mitigate the discomfort and urgency. One effective approach involves taking over-the-counter nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen, which are prostaglandin inhibitors. Taking an NSAID just before the period starts may help lower prostaglandin production, reducing both uterine cramping and bowel contractions.
Adjusting your diet during this time can also offer relief.
Dietary Adjustments
Focus on easily digestible foods and increase your intake of soluble fiber, found in items like oats and bananas, to help regulate stool consistency. Maintain high fluid intake to replace water lost due to increased bowel frequency and to support overall digestive health.
Temporarily limiting common gut irritants like excessive caffeine, spicy foods, and high-fat items can reduce the stimulation of the sensitive digestive tract. If bowel activity is severe or significantly disrupts daily life, mild anti-diarrheal medications can be considered for short-term relief.