Published On: 07/07/20211036 words5.2 min read

Your gut microbiota (gut flora) is the name given to the huge microbe population living in your intestine. This micro-biome, contains a variety of bacteria, viruses and yeast that live and are natural to your gut. The gut also houses the majority of your immune system – 70-80% of our immune cells are found here. Our immune system has co-evolved along with a diverse gut flora, not only to create defences against pathogens, but also to develop permeability for beneficial microbes.

If you suffer from Endometriosis, you likely also suffer with the bloating, other digestive symptoms and ‘endo belly.’ These digestive symptoms such as constipation and diarrhoea are common in women who have endometriosis. Many of the symptoms present the same in both endometriosis and IBS. Women are often diagnosed with IBS before they are diagnosed with Endometriosis. Another interesting thing to note is that endo-belly seems to occur regardless of the location of endometriosis. This means, that you could be experiencing gastrointestinal symptoms without endometriosis being located on the bowel.


The intestinal wall is the primary defence between the gut microbiota and our body. It acts as a barrier that separates our body from gut microbes but allows desirable interactions to take place. A healthy intestinal barrier will keep pathogens and harmful microbial products away from our body while being permeable to the healthy molecules. Leaks in the intestinal barrier alter its permeability and lead to what is commonly known as “leaky gut.” Leaky gut, also known as intestinal permeability, can happen when external factors, like food intolerance to things like gluten, infections, toxins, and stress break apart the tight lining in your intestinal wall. This means potential toxins, microbes and undigested food can now pass through into your bloodstream, creating an immune response to the invaders. Our immune system reacts by sending out wave after wave of inflammation to attack the foreign invaders. Some common infectious causes are Candida overgrowth, intestinal parasites, gram negative bacteria and SIBO, or small intestine bacterial overgrowth.

In endometriosis, there’s also imbalances with the pelvic micro-biome, vaginal micro-biome, and uterine micro-biome.

  • SIBO

Most of the bacteria that lives in our gut is located in the large intestine. SIBO occurs when there is too much in the small intestine. The small intestine is mostly reserved for absorbing nutrients. The overgrowth of bacteria in the small intestine can cause a number of symptoms such as constipation and/or diarrhoea, abdominal pain and bloating. It also creates widespread inflammation, leading to leaky gut and other gastro-intestinal issues. There’s a greater chance of women with endometriosis developing SIBO due to the adhesions or scar tissue, which can interfere with the normal digestive processes.


Key microbes have been identified in women with endometriosis, implying that endometriosis or at least the inflammatory property of endometriosis could be a result of microbial imbalance. A study published in 2017, looked at the link between microbial dysbiosis and disease pathogenesis of endometriosis. Another study in 2018, also looked at bacterial contamination and both seemed to come to a similar conclusion.

They found in women with Endometriosis, the menstrual blood was high in gram negative bacteria, specifically Escherichia coli (E. Coli), a type of bacteria known to produce a toxin called lipopolysaccharide (LPS), which produces an inflammatory response. This modification in the microbial population was shown to have the capacity to reduce immune efficiency. Both studies also showed new support for the retrograde menstruation theory because it could be what is moving the bacteria into the endometrium and tissue to the other sites. It is also not quite known yet which one comes first – if endometriosis causes different bacteria to live in the uterus, or if different bacteria actually trigger endometriosis.

The bacterial toxins are potentially leaking into the pelvis where there are inflammatory lesions present. Bacteria aren’t supposed to move from the gut to other locations in the body, this only tends to happen when the integrity of the intestinal lining is compromised which is why the leaky gut connection might be so important.


The gut micro-biome also has the potential ability to impact oestrogen levels. When you have an imbalance of gut bacteria – from a lower number of beneficial bacteria, a potential overgrowth of ‘bad’ bacteria, or even yeast/parasites can occur – this is known as dysbiosis. Gut dysbiosis may lead to the production of an enzyme called beta-glucuronidase.

When your liver metabolizes oestrogen, it labels it and sends it down to your bowels to be excreted. If you have dysbiosis and constipation, your labelled or marked oestrogen is often sitting in your large intestine much longer than usual. Bacteria producing beta-glucuronidase can act on this marked oestrogen and un-mark it, which allows it to become free and re-enter your system.


Nickel sensitivity and/or allergy have also been linked to be a potential cause or a further inflammatory trigger in Endometriosis. A nickel allergy or sensitivity could create an immune response when someone comes into contact with a product containing nickel either externally with things like nickel containing jewellery or stainless steel cooking equipment or internally with some higher risk foods (depending on the nickel content in the soil) like oats, buckwheat, multi-grain breads, brown rice, some seeds like alfalfa and sesame, some seafood, legumes like chickpeas, vegetables like cabbage and kale and cocoa beans.

A case control study completed in 2015 found that nickel allergy is a risk factor for endometriosis it also assessed the affect nickel has on endometriosis due to the oestrogenic effects of nickel. You can read about the study here:

A further study publishes in January 2020 further established a link between Endometriosis, IBS and nickel sensitivity.

A low nickel diet and reducing exposure can potentially be beneficial depending on your sensitivity. A nickel patch test can be done by your Doctor or dermatologist. It is testing for Atopic dermatitis, but an external reaction would likely indicate that it might be causing an immune reaction inside the body as well from foods containing high nickel. I do not often use food intolerance testing as they are extremely expensive and results can be inconsistent.

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