5 Weird Things You Never Knew About Your Period

Think you know your flow? #5 will blow your mind.

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Your Friday night “girl talk” is about to get a little more interesting.

Ever wonder why the female reproductive system is such a mystery? (And we’re not just talking about orgasms.) Women’s menstrual cycles are so subtly complex, scientists are still uncovering new and interesting findings about them.

From chocolate cravings to “synced periods” to what’s actually in period blood, here are five bizarre facts about your flow (we bet #5 will blow your mind!).

  1. Craving chocolate? Yea, there’s a reason for that. During the luteal phase of the menstrual cycle, which occurs right before your period starts (a.k.a. PMS), your hormone levels fluctuate, which can lead to cravings and a rollercoaster of emotions. When it’s almost that time of the month, keep healthy(ish) snacks nearby, or try one of these non-food ways to curb cravings.

  2. It’s OK to not get a period when you’re on birth control. While voluntarily suppressing your period may seem “unnatural,” there’s actually no medical reason not to skip it. During a normal cycle, the uterus lines itself to prepare for pregnancy, then sheds it (hello, period!). If you’re on hormonal birth control, however, you don’t build that lining, so your body has nothing to shed. The only time you actually need that lining is when you want a baby. Want to learn more about it? Here, an Ob-Gyn explains why it’s safe to skip your period while using BC.

  1. “Synced periods” are myth (sorry). As much fun as it is to bond with your friends over periods that seem to start and end at the same time, it’s just a theory, and there’s not much scientific evidence supporting it.

  2. Some of your furry friends have periods, too. Thought humans were the only animals with a menstrual cycle? Think again. Certain primates, bats, rodents, and dogs also bleed. These animals’ periods, however, are a little different than humans’. For instance, female dogs tend to only bleed when they’re in heat, once or twice a year.

  3. Your menstrual blood contains more than 380 unique proteins—and more than 1,060 types of protein total. It’s also full of circulatory blood (the kind that’s in the rest of your body), cells, and vaginal secretions.

On a menstrual cycle fact kick? Here’s why you get menstrual cramps, plus, tips to ease menstrual cramps during that time of the month.