Why do we sometimes have diarrhoea during our period?

Why do we sometimes have diarrhoea during our period?

Your period is approaching and you're starting to feel sick. In addition to stomach pains, which affect nearly 60% of menstruating people(we give some tips on how to fight against these pains here), there is an even more taboo unpleasantness that accompanies menstruation and/or premenstrual syndrome for a large part of us: diarrhoea. What causes diarrhoea during your period and how can you alleviate it (and the pain associated with it)? We answer in detail.

Diarrhoea during menstruation or premenstrual syndrome: a common digestive disorder, a huge taboo.

According to a 2014 study (1), 73% of menstruating people experience gastrointestinal symptoms during their period. These include the well-known stomach ache, but the second most common digestive complaint is diarrhoea, which occurs in 24% of people before their period and 28% during their period. This is followed by other transit-related symptoms such as constipation, nausea, flatulence or bloating and even vomiting. 

Unfortunately, we don't talk about it much. Even a few years ago, we didn't talk about menstruation (and still some people are still embarrassed), so menstruation AND poo are the ultimate combo! In the end, we sometimes feel helpless when faced with this problem. The proof? It's much more acceptable to say "I have a stomach bug" than "my period is making me feel sick". So know that you are not alone and that it is normal, it is part of the classic cycle problems, beyond the cramps and pain of dysmenorrhoea.

Why do I have diarrhoea during my period?

The cause of this diarrhoea is a hormone: prostaglandins.

These are hormones that are synthesised on demand by the body in response to a specific stimulus. Almost all organs and tissues are able to produce them. One of their functions is to promote muscle contraction. 

By the time your period approaches, the endometrium - the lining of the uterus - has become covered with blood to accommodate a possible fertilised egg. If there is no fertilised egg, your body prepares to evacuate this tissue and menstrual blood accumulated on the uterine lining: this is the period. This is why your endometrium starts to produce prostaglandins a little before your period: to promote the - sometimes painful - contractions and cause menstrual bleeding.

But once the hormones are released by the endometrium for this purpose, they pass into the bloodstream and sometimes reach the digestive system, causing your intestines to become active. And faster digestion means a high risk of diarrhoea or nausea... 

These disorders, such as uterine cramps, are therefore a 'simple' side effect of a rather well thought-out body function. 

How to limit diarrhoea problems during menstruation?

Now that you know the causes of the pain, you may be wondering how to relieve or limit the diarrhoea. Here too, the starting point is prostaglandins.

In fact, they are made from specific fats: arachidonic acid and linoleic acid.

Generally speaking, these polyunsaturated fatty acids from the omegas-6 family are good for the body. They are even essential fatty acids that play an important role in brain health, in the fight against cardiovascular disease and in strengthening the immune system. 

But if you consume too much before your period, they can lead to an overproduction of prostaglandins, which will amplify your transit problems, even cramps and nausea by amplifying the contractions of your muscles. 

That's why it's often said that you shouldn't eat too much fat before your period, but that's a generalization (and you can eat fat if you feel like it, you just need to know what kind of fat we're talking about).

So let's be precise: here are the foods richest in these two acids so that you can avoid them temporarily if you are prone to menstrual diarrhoea. Our advice: eat them every day and get off your feet a little before your period.

The foods richest in arachidonic acid : 

Cod liver oil, tuna in oil, roast pigeon and goose, duck confit/breast, sardines in tomato sauce, chocolate cake, andouilette, minced steak 20%MG, country pâté, leg of lamb, egg, beef, dry sausage, Toulouse sausage, ham.

A word of clarification: oily fish and eggs are still recommended if you do not have diarrhoea, as they are very rich in Vitamin D, which combats menstrual pain.

The foods richest in linoleic acid : 

Grapeseed oil, walnut oil, sunflower oil, corn oil, soybean oil, wheat germ suite, sesame oil, walnuts, pine nuts, poppy seeds, sunflower seeds, peanut oil, pecan nuts, sesame seeds, pumpkin seeds, rapeseed oil, pistachios

If you still have diarrhoea (which usually lasts only 1 or 2 days), there is no magic treatment. Act as you would during a stomach bug: eat rice (white, not wholemeal), cooked carrots or courgettes, or turn to the specific medicines for temporary diarrhoea.

Beware of endometriosis!

Diarrhoea is often commonplace but can also be a symptom of endometriosis.

Endometriosis is a very common gynaecological disease, affecting about 1 in 10 menstruating women. It is the presence outside the uterine cavity of tissue similar to the uterine mucous membrane, which will be influenced by hormonal changes during each subsequent menstrual cycle (2). Endometriosis is responsible for chronic disabling pelvic pain and in some cases infertility. 

When endometriosis develops in the intestines, colon or rectum, it can cause digestive problems such as alternating diarrhoea and constipation (a symptom that is aggravated at the time of menstruation), pain when you have a bowel movement, and sometimes the presence of blood in the stools. 

The diagnosis of endometriosis is complex because there are many forms of the disease, each with different symptoms. We advise you to find out more on the Endofrance website and to talk to your doctor, gynaecologist or midwife if you have any doubts. 

What about constipation? 

This is another of the common bowel symptoms associated with menstruation. 

The mechanism that triggers this constipation is less well studied by doctors, but it seems that the sudden drop in ovarian hormone levels (oestrogen and progesterone) just before the period also stops the contractions of the digestive system in some people that allow food to move through the digestive system. With transit stopped, food stagnates and ferments, which can lead to bloating, aerophagia and constipation. 

If you experience these symptoms during your cycle, eat foods rich in fibre that will help your transit (prunes, almonds, dried apricots, 70% dark chocolate, chickpeas, lentils, wholemeal bread, etc.) 


Related articles: 

The composition of menstrual blood is an incredible resource 

9 natural solutions for menstrual pain


Notes : 

(1) Bernstein et al, Gastrointestinal symptoms before and during menses, BMC Women's Health, 2014, 14:14

(2) definition of Endofrance association

At Luneale we have chosen to write inclusively, because we are aware that some women do not have their periods, and that not everyone who has their period is a woman. But search engines need us to write 'women' in articles related to menstruation for us to be visible. So we do it here! :)



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