The Sensitive Gut

Understanding IBS

It’s that time of the month again. So why do I feel so bad?


pms.590There can be few women who do not experience some variations the way they feel during their menstrual cycle, but in those of you who have IBS, those feelings can be painful and  distressing.  Women with IBS  tend to suffer more from painful menstruation (dysmenorrhea) and premenstrual syndrome (PMS) than those without.  But for most women with IBS, their menstrual symptoms are focused on the gut.

In particular, abdominal pain, nausea and diarrhea tend to increase just before a period and reach a crescendo on the first to second day of menstrual flow.  You may also suffer from fatigue, backache, and insomnia during menstruation and may experience greater sensitivity to particular FODMAP foods at that time.  Physiological recordings have shown that rectal sensitivity is exaggerated during menstruation in women with IBS.

Bloating and constipation, on the other hand, tend to be more of a feature after ovulation, which occurs  between 10 and 14 days after the onset of bleeding, and builds towards the end of the cycle.


What happens during the menstrual cycle? 

After menstruation, oestrogen is secreted by the a group of cells, known as the follicle that encloses the developing ovum or egg.  Oestrogen levels rise during the follicular phase of the cycle, reaching a peak at around 10 to 14 days, when the follicle bursts and the ovum is released from the ovary to begin its journey down the fallopian tube, where if fertilized by invasion of spermatozoa, it may embed in the uterus.  At ovulation, some women may experience a sharp episode of lower abdominal pain, known as ‘mittelschmerz’, which may represent irritation of the peritoneum caused by bursting of the follicle.

After ovulation,  the follicular remnant is transformed into a group of cells known as the corpus luteum, which supplements the secretion of oestrogen with an admixture of progesterone.  The combination of progesterone and oestrogen continue to rise during the luteal phase of the menstrual cycle.  This makes the lining of the uterus soft and receptive to the fertilized ovum, but it also has several effects on your sensitive gut.  These include inhibition the gastric emptying, delays in colonic propulsion and symptoms of nausea, heartburn, bloating and constipation and bloating.  You may also put on weight during this period, often due to fluid retention.

If the ovum fails to implant in the uterus and take over production of hormones, the corpus luteum fails and both oestrogen and progesterone fall abruptly as the uterus sheds it’s lining  at menstruation together with chemicals known as prostaglandins, which may be partly  responsible for the diarrhoea and increases in sensitivity that occur at that time.


Are fluctuations in symptoms related to levels of reproductive hormones? 

It is likely that the changes in IBS symptoms during your menstrual cycle are related to the fluctuations in levels of reproductive hormones, though studies have not shown that hormone levels are any different in IBS.


Effects on mood

The physiological changes that occur during the menstrual cycle are also associated with changes in your mood.  The first part of the cycle from the end of menstruation to ovulation is likely to be the most contented.  During this phase, you may experience greater optimism as the rising levels of oestrogen suppress the effects of the stress hormones adrenaline and cortisol.  At ovulation,  the balance of gonadotrophin regulatory hormones from the pituitary gland changes (luteunising hormone (LH) replacing follicle stimulating hormone (FSH)) and this together with oestrogen and other hormones, such as insulin and testosterone to increase libido, which may encouraging you to have sex during your most fertile time.  Consumer studies also suggest that you may be more likely to buy clothes, makeup, and other items to make themselves more attractive at that time.  You may also have a greater tolerance to pain at this time.

As progesterone levels rise towards the end of the cycle, you may become more irritable, and depressed and cry more easily.  Even small things like deciding what food to buy for the family or what to wear can assume unrealistic proportions.  You might also drink more alcohol and crave high calorie foods, which could further upset your mood and exacerbate your IBS.  This may happen because high progesterone levels increase the activity of the amygdala, a nucleus in the brain stem responsible for emotional reactivity and stimulate the production of stress hormones.   Women who are already busy and under stress tend to experience more severe premenstrual distress, which, if they already have IBS, may make the symptoms a lot worse.


How you can learn to cope with menstrual symptoms

If you suffer from severe IBS symptoms during your menstrual cycle, use a diary or symptom tracker to plot your menstrual cycle and track your symptoms alongside changes in diet and life events.  This may allow you to discern a pattern and help you plan what to eat or what medications to take.  Although the menstrual symptoms of IBS can be hard to deal with, you can relieve them  by taking control and adopting a healthier life style, getting adequate rest and sleep, avoiding unnecessary stress, eating healthily and restricting alcohol.

Although there is no evidence that women with menstrual distress and IBS have abnormal hormone levels, some may find that taking oral contraceptives relieve their symptoms.


So why do you have periods anyway.

Forgive this digression, but it’s kind-of interesting.

It’s only some primates, a few bats and the elephant shrew that have periods.  Most animals don’t.   They have an oestrous cycle instead and come ‘on heat’ maybe once or twice a year when environmental conditions are right.  Other times, they are just not interested.  During your fertile years, you can be sexually active at any time.  This probably enhances the pair bond necessary for the prolonged rearing of your children, but it also means that your developing embryo may be a few days old before it implants.  For reasons I don’t understand,  human embryos are more susceptible to genetic abnormalities.  The luteal phase of the cycle allows the developing embryo to burrow deep into the uterine lining and come into intimate contact with your blood supply, which enables the immune system to detect abnormalities and eliminate the defective embryo along with the uterine lining so you can try again during the next cycle.



Heitkemper MM, Jarrett M. Pattern of gastrointestinal and somatic symptoms across the menstrual cycle (1992). Gastroenterology;102: 505–13.

Houghton LA. Lea, R, Jackson N and Whorwell PJ (2002) The Menstrual cycle affects rectal sensitivity in patients with IBS but not healthy volunteers.  Gut  2002;50:471-474

Sundström Poromaa, I., & Gingnell, M. (2014). Menstrual cycle influence on cognitive function and emotion processing—from a reproductive perspective.Frontiers in Neuroscience8, 380.

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This entry was posted on July 15, 2016 by in Bloating, Gender, menstrual cycle, sensitivity and tagged , , .

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