Sorry, guys. You’re excused for this one.
Many women experience bowel changes around their periods (and sometimes ovulation too). While some women get more constipated, most get looser stools during ovulation and menses. Here’s why.
Ovulation Bowel Changes
You can have bowel changes around ovulation for the same reason that some women get pain with ovulation (also called mittelschmerz): the body releases an inflammatory compound called prostaglandins in order to trigger the contraction of the follicle to get it to release the egg. (Prostaglandins incidentally are also the compound that gets blocked when you take NSAID painkillers, like Motrin or Advil.) This is a physiologic process, but too much of it can cause pain. It can also cause contraction of other nearby structures, like the bowels. This can speed up motility, leading to loose stools (and possibly cramping too).
Luteal Phase Bowel Changes
The first half of the menstruation cycle is called the follicular phase, lasting from the time of the previous period until ovulation. It is characterized by a rise in estrogen primarily, to thicken the endometrial lining for implantation, should it occur. The second half of the cycle is called the luteal phase, characterized by the rise in progesterone. Progesterone is the “pro-gestation” hormone: it helps to tonify the endometrial lining. But it also tends to slow down gut motility, which can lead to more constipation for some women during this phase.
Period Bowel Changes
Back to prostaglandins: these inflammatory compounds also trigger the uterus to contract, shedding the endometrial lining during the period if implantation does not occur. Again, since prostaglandins cause contraction (and cramping, and possibly pain), this can lead to looser stools too.
The other reason why some women might experience more loose stool around their periods than even around ovulation is due to the sudden drop in progesterone (which, again, can have more of a constipating effect during the luteal phase). When it dips during actual menses, the lack of it can cause stool to loosen as well, compounding the effect of the prostaglandins.
On the flip side, if you tend to stress-eat before your period to compensate for the loss of estrogen and progesterone (which can make you moody), you might over-compensate and end up constipated. That’s because simple carbs and sugar, which might temporarily lift your mood, will likely replace high fiber foods–and fiber, of course, keeps your bowels moving properly.
What To Do About It
Essential fatty acids won’t block prostaglandin production like NSAIDs will, but they will shift the body toward production of anti-inflammatory compounds that balance out their effects. I recommend about 1000 mg of EPA daily for most people, but consider doubling it in the week leading up to and during your period (or also leading up to ovulation, if you have bowel changes and pain then too).
Magnesium, ironically, also lowers prostaglandins quite effectively. I say ironically because magnesium usually has a laxative effect, but for a different reason: it draws water into the colon. For women whose bowels tend to be looser due to prostaglandins, magnesium will lower those levels, with a net effect of regulating the bowels (not to mention lessening period pain). I usually start women with 200-400 mg of chelated magnesium (basically any kind of magnesium that’s not oxide, sulfate, or carbonate) during the week before the period. You can titrate your dose from there.
Eating clean around your period especially will also help to decrease overall inflammation, which will lower circulating levels of prostaglandins as well.