Period poos: why do they happen and how can you deal with them?
The menstrual cycle affects many aspects of the body and the bowels are no exception. You aren’t imagining it. Period poos are a real thing.
What exactly do we mean by “period poo”?
The defining feature of period poos is that they are different to others in your cycle – likely less pleasant (we know, what a joy) (1). They might be harder, softer, come more or less frequently, have a different colour, stronger odour or even cause more bloating and pain (2). Generally speaking, you might experience firmer and less frequent stools before your period during the luteal phase and once your period begins find that these become looser and more frequent (3).
Why does it happen?
We have a few culprits. First off, prostaglandins – those little messengers that signal the start of your period by telling your uterus to contract (a.k.a menstrual cramps) can also affect other nearby muscles such as those in the gastrointestinal tract (GI) (4). This is partly why the contracting and relaxing of the muscles in the digestive tract changes around your period and might result in more frequent bathroom trips – it is not just your uterus contracting more regularly but also the bowels (5).
Secondly, of course, your hormones (when in doubt, blame hormones). There are sex hormone receptors along the GI tract, and fluctuations in these hormones affect the internal workings of the gut (6). High progesterone can slow digestion and result in varying degrees of discomfort (such as stomach ache and constipation), which may be more prevalent when levels are high a week or so before a period starts (7). When the hormone responsible for slowing the digestive system drops, the gut motility speeds up and the body is less able to reabsorb water and nutrients as quickly (8). Enter your foe diarrhea.
You may also experience digestive discomfort due to stress levels or dietary changes (such as those naughty but delicious PMS cravings) (9, 10).
Is it normal?
It is oh so normal and common to experience the dreaded “period poo”. Approximately three-quarters of women with cycles have gastrointestinal symptoms premenstrually and two-thirds have them during their period (with abdominal pain and diarrhoea being the most common symptoms) (11). So while the topic might seem taboo, the period poo experience is extremely common. There really is nothing to feel shameful about. These GI symptoms are experienced more significantly in participants with a history of painful periods (12) and other conditions such as Irritable Bowel Syndrome (IBS) (13) and Irritable Bowel Disease (IBD (14).
Is there anything you can do to help with period poos?
We spoke with dietician Kiah from the PNW clinic to learn more about what can help reduce your unpleasant period poo experiences. The good news is that if you are finding yourself unnecessarily hunched over the toilet from period poos, diet and exercise can make a positive difference! She suggests “increasing the amount of soluble fibre in your diet.” This type of fibre is dissolved in water and helps to thicken the stool making it slow down as it moves through the digestive tract (15). Foods rich in soluble fibre include banana, oats, chia seeds, psyllium husk and legumes. For instance, “starting the day by having oats for breakfast, adding psyllium husk to a smoothie or including a banana as a snack!”.
What about constipation?
If you’re someone who is more prone to experiencing constipation during their menstrual cycle, you also want to make sure you’re drinking enough water and doing some form of exercise, even just walking! (16) “Both of these things can help to keep our digestive tract functioning regularly.”
On top of this, it may be helpful to monitor what is happening down there. As with tracking your period, you can also track your digestion. A great tool for monitoring is Cara Care, which can track patterns of eating, symptoms, and stool consistency (we swear that it’s not as unpleasant as it might sound).
Should you see a doctor?
Period poop should never get in the way of daily life (nor should any other PMS symptom for that matter), so if your GI changes are causing you distress, impacting your quality of life or simply bothering you, speak with your healthcare provider.
Zoe Sever is Unfabled's Clinical Lead. Zoe brings a wealth of knowledge from her broad spanning background, having started her career in Nursing and transitioning to Sexology and Research. She holds a Master’s in Sexual and Reproductive Health and is currently pursuing a PhD in Women’s and Reproductive Health at Oxford University. On a mission to empower individuals with cycles to better understand their bodies, Zoe is helping us to banish shame, stigma and demystify reproductive health.
- Björnsson B, Orvar KB, Theodórs A, Kjeld M. [The relationship of gastrointestinal symptoms and menstrual cycle phase in young healthy women]. Laeknabladid. 2006;92(10):677-82.
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- Crowell MD, Dubin NH, Robinson JC, Cheskin LJ, Schuster MM, Heller BR, et al. Functional bowel disorders in women with dysmenorrhea. Am J Gastroenterol. 1994;89(11):1973-7.
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- Guarino M, Cheng L, Cicala M, Ripetti V, Biancani P, Behar J. Progesterone receptors and serotonin levels in colon epithelial cells from females with slow transit constipation. Neurogastroenterol Motil. 2011;23(6):575-e210.
- Judkins TC, Dennis-Wall JC, Sims SM, Colee J, Langkamp-Henken B. Stool frequency and form and gastrointestinal symptoms differ by day of the menstrual cycle in healthy adult women taking oral contraceptives: a prospective observational study. BMC Women's Health. 2020;20(1):136.
- Liu Q, Wang Y, van Heck CH, Qiao W. Stress reactivity and emotion in premenstrual syndrome. Neuropsychiatr Dis Treat. 2017;13:1597-602.
- Blanchard EB, Lackner JM, Jaccard J, Rowell D, Carosella AM, Powell C, et al. The role of stress in symptom exacerbation among IBS patients. Journal of Psychosomatic Research. 2008;64(2):119-28.
- Moore J, Barlow D, Jewell D, Kennedy S. Do gastrointestinal symptoms vary with the menstrual cycle? Br J Obstet Gynaecol. 1998;105(12):1322-5.
- Whitehead WE, Cheskin LJ, Heller BR, Robinson JC, Crowell MD, Benjamin C, et al. Evidence for exacerbation of irritable bowel syndrome during menses. Gastroenterology. 1990;98(6):1485-9.
- Lim SM, Nam CM, Kim YN, Lee SA, Kim EH, Hong SP, et al. The effect of the menstrual cycle on inflammatory bowel disease: a prospective study. Gut Liver. 2013;7(1):51-7.
- Heitkemper MM, Chang L. Do fluctuations in ovarian hormones affect gastrointestinal symptoms in women with irritable bowel syndrome? Gend Med. 2009;6 Suppl 2(Suppl 2):152-67.
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- Gao R, Tao Y, Zhou C, Li J, Wang X, Chen L, et al. Exercise therapy in patients with constipation: a systematic review and meta-analysis of randomized controlled trials. Scandinavian Journal of Gastroenterology. 2019;54(2):169-77.