The Science Behind Period Farts

For you who have or have had girlfriends, you might be aware of that time of the month when your better part starts being cranky, eating toffee with ketchup and letting off more gas in one evening than Gazprom does in a year.

Why do women fart so much before our periods?

The sex hormone cycle is quite the intricate thing in women and these hormones  absolute and relative concentrations can make you go from a sex-ravenous and splendid dame  to a cranky, hungry and pooping miserable pile of [beeep] within the course of a couple of weeks.

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The hormonal cycle

Estrogen is the hormone that peaks around ovulation and the hormone progesterone reaches its peak right before your period. Thus, this hormone is thought to be one of the villains of this story and cause havoc with our poor intestines a few days before the bleeding starts.


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Symptoms of high progesterone can be bloating, constipation and gas partly due to the dampening effect on the smooth muscles of the digestive tract. This dampening effect causes the intestines to work slowly and gives more time for gut bacteria to ferment the food and release gaseous compounds. If you are interested in the different chemical components of flatulence, or would like to be able to tell which compound is dominating the fart just by smelling it, please check out my post on flatulence: The Science Behind Farts.

When the period starts, the hormone-like compounds: prostaglandins increase. They causes cramping and the uterus contract to slough off the uterine lining and cause a bleeding. Prostaglandins also cause contractions of the smooth muscles in the digestive tract and thus intestinal cramping that for some women lead to the development of gas.

The gut microbiota

These quite spectacular hormonal changes can also have quite strong effects on the gut microbiota. Different groups of gut bacteria might take over and if your stomach in addition works extra slow due to the hormonal changes, there will be loads of time for these bacteria to start fermenting your food. This fermentation causes gas.

Sadly, if you have irritable bowl syndrome (IBS), it is likely to be much worse before your period than during other times.

Two kilos of cheese

Lastly, those farts might have something to do with those three bags of Doritos or those two kilos of Gruyere cheese you just ate.

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What to do?

If you, or your girlfriend, suffer from period farts, my tip would be to cut down on coffee, stress less eat sensibly and for some people non-steroidal anti-inflammatory drugs sometimes work. Because they reduce prostaglandins – but ask your doctor about that because I am not qualified to dish out medical advice. I am not like David Avocado Wolfe who dishes out medical advice despite of having no clue about medicine at all. At least I have a Ph.D. in biology.

Another more unconventional way to deal with the farting problem is to get a dog and blame it all on her. Just hypothetically I mean..

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A girl’s best friend.

Science Safely!

Photography: Judith Klapper, Berlin (copyrighted)

Dr. Anna checking out some gas. Photography: Judith Klapper, Berlin (copyrighted)

Here is the video to this post:

Posted in Biology, Medicine, The Biology of Disgusting and tagged , , , .

Dr. Anna

Dr. Anna Zakrisson is a multifaceted biologist with degrees from world-renowned institutions such as Cambridge University, U.K. and the Max-Planck Institute in Germany. She has published a range of high-ranking scientific papers and crossed oceans on research vessels. She runs The Imaginarium science blog and YouTube channel and speaks English, German and Swedish fluently.

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