In the morning, your jeans do up. By the evening, your belly is as tight as if you were five months pregnant, and it pulls right round to your back. In patient groups, it even has a nickname, endo belly.
In Sydney, researchers compared 26 women whose endometriosis had been confirmed by laparoscopy with 25 women without it. Bloating affected 96% of the first group, against 64% of the second. During flare-ups, 87% of them had to wear loose clothes, against 38%. Their waist measurement, taken three times a day for a whole cycle, also varied far more (Luscombe et al., 2009).
For many women, endometriosis is felt as much in the gut as in the pelvis.
A close link with irritable bowel
Women with endometriosis are two to three times more likely to have irritable bowel syndrome. An Italian meta-analysis of eleven studies put figures on it in 2021. They are about three times more likely than other women to also have IBS, and the studies that followed women over time found about twice the risk of developing it after diagnosis (Chiaffarino et al., 2021).
Many are told they have IBS first, sometimes for years, before anyone thinks of endometriosis. The two conditions share background inflammation, more sensitive nerves, and often an unbalanced gut microbiome. In New Zealand, among 160 women seen for IBS, 36% also had endometriosis. In these women, gut symptoms that got worse during periods, pain during sex and a mother or sister with the condition came up far more often (Moore et al., 2017). If you have been told you have IBS and you recognise these signs, talk to your gynaecologist.
A gut that feels things more strongly
In Manchester, a team inflated a small balloon in the rectum of women who had surgery for pelvic pain, to measure at what pressure it started to hurt. Those with endometriosis, even minimal, felt pain at around 28 mmHg, against 40 in women without symptoms. Their threshold looked like that of patients with IBS, and between half and two thirds of them had IBS symptoms (Issa et al., 2012).
The authors see this as the explanation for a common paradox. Lesions judged minimal during surgery can hurt a great deal, because an oversensitive gut amplifies the pain.
Mast cells, between lesions, nerves and the gut
Mast cells are immune cells that release histamine and other inflammatory substances. In Brussels, a team counted them in the lesions of 69 women operated on for pain. There were far more than in healthy tissue, especially in deep lesions, the most painful ones, where many sat right against the nerves (Anaf et al., 2006).
They are also found in the gut wall, and oestrogen activates them. This mechanism could explain both part of the pain and the link with digestive problems. Food that calms inflammation, a balanced microbiome and enough sleep help settle them.
The microbiome and oestrogen
Gut bacteria take part in recycling oestrogen. Some make an enzyme, beta-glucuronidase, that reactivates oestrogen meant for elimination and lets it pass back into the blood (Baker et al., 2017). When the microbiome is out of balance, some of the oestrogen that should have left can be put back into circulation, which can feed the lesions.
A 2020 review gathered the studies comparing the microbiome of women with and without endometriosis. Certain bacteria, such as E. coli and others from the same large family, turn up more often in women with the disease, in the gut as well as the reproductive tract (Leonardi et al., 2020). The link runs both ways, and research does not yet know which comes first. Repeated antibiotics, stress and a diet low in vegetables all add to the imbalance.
What helps your belly
When your gut is sensitive, raw, hard vegetables are hard to digest. Raw cauliflower, broccoli or cabbage ferment in the gut and make you bloat. Eat them cooked, or fermented like sauerkraut or kimchi. Lettuce, cucumber or avocado usually go down without trouble and can stay raw. I have gone through which vegetables to cook first in the article on raw or cooked vegetables.
Cooked vegetables bring the fibre your good bacteria feed on. Fermented foods, sauerkraut, kimchi, kefir or plain yoghurt depending on how you tolerate them, bring new ones. Introduce them slowly, a teaspoon at first, to give your gut time to adjust. With dairy, tolerance varies a lot from one woman to the next. If it makes you bloat, set it aside for a few weeks and watch what happens.
When bloating and gut pain take over, a low FODMAP diet, cutting the sugars that ferment heavily in the gut, can bring clear relief. In the New Zealand study, after four weeks on this diet, 72% of the women with endometriosis saw their gut symptoms drop by more than half, against 49% of the women with IBS alone. It is a retrospective analysis, of women seen in a specialist clinic. The diet is only followed for a few weeks, ideally with support, before bringing foods back one by one. Kept up too long, it makes the microbiome poorer. I explain where FODMAPs come from in the article on bloating.
For one cycle, note your waist measurement every evening, what you ate and the day of your cycle. A tape measure and a notebook are all you need. You will soon see whether your belly follows your meals, your periods or both, and so will your doctor.
This article is for information only and does not replace medical advice.