If you’re like most people, you’re sometimes mystified by your bowels. You may go through weeks’ long stretches of perfectly consistent pooping after your third sip of coffee, but then wake up one morning to find the urge never hits. You may have random diarrhea that strikes without warning, or random constipation that clears up after a day or two.

There are obviously many things that can cause your bowel frequency or consistency to change, including diet, stress, illness, and food intolerances. But one factor that many women overlook is the menstrual cycle. 

Diarrhea During Your Period?

It’s common to notice digestive changes during the first few days of your period. You may have more gas, have to go to the bathroom more, or even have diarrhea. What you’re experiencing when this happens is a one-two punch from progesterone and prostaglandins. 

Progesterone Slows Things Down

Right after ovulation (about 12-14 days before your period for most women), your progesterone level rapidly rises. Progesterone is a muscle relaxant. It’s even given to pregnant women to delay labor and preterm birth because its relaxing effects are strong enough to counteract uterine contractions. This relaxing effect is also slightly constipating (this is also why so many pregnant women complain of constipation—progesterone levels are so high during pregnancy that it can make it hard to get things moving down there).

Stool moves through the bowel via peristalsis, the process of the muscles lining the bowel contracting and relaxing to create a rippling, wave-like motion to move things though the intestines. Progesterone can mute this effect. You may even notice that you become slightly constipated after ovulation. 

Just before you get your period, your progesterone levels fall rapidly, and it can feel like the levee breaking: the hornone responsible for slowing everything down is suddenly absent.  

But progesterone isn’t the whole story. Prostaglandins are also responsible for loosening things up during your period.  

Prostaglandins Speed Things Up 

These hormone-like lipids are to blame for your period cramps. They cause the uterus to contract to expel the uterine lining. If you have a lot of prostagladins, some of them can go rogue and head over to the nearby bowel, causing it to contract too. This can lead too farting, more pooping than normal, and for some women, even diarrhea. (Side note: prostaglandins can also spread to the brain, causing migraine headaches.)

Now that you understand the relationship between the menstrual cycle and digestion, what’s a constipated or diarrhea-afflicted girl to do? 

How to reduce pre-menstrual constipation:

  1. Magnesium. Taking 400 – 800mg of magnesium per day can help with constipation. Magnesium glycinate is the most easily absorbed form, and is less likely to cause diarrhea.
  2. Patience. By the time your period comes around, the drop in progesterone should help things get moving again. 

How to reduce gas and diarrhea during your period:

  • Prostaglandins are pro-inflammatory, so anti-inflammatories can help counteract their effect. Curcumin, a powerful ingredient in turmeric, is anti-inflammatory. Try some turmeric honey tea
  • Increase your intake of omega 3 fatty acids. If sardine sandwiches aren’t your thing (don’t knock it til you try it!), you can take a cod liver oil supplement.
  • Eat foods with high levels of resveratrol: think red grapes, blueberries, and cranberries. 


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