Irritable bowel syndrome (IBS) and endometriosis are two chronic conditions that can cause significant pain and discomfort for suffers. IBS affects approximately 5-10% of the population and is a functional gastrointestinal disorder, meaning that there are no structural abnormalities to explain the symptoms (Ford et al, 2020). Although the exact cause of IBS is unknown, it is thought to develop due to a miscommunication between the brain and the gut motility, visceral hypersensitivity, and altered central nervous system processing, although changes in gut microbiota, genetics and the enteric mucosal immune system may also be involved (Ford et al, 2020).
Endometriosis, on the other hand, is a chronic inflammatory condition that involves the ectopic growth of endometrial tissue outside the uterus, most commonly in the abdominal cavity, but it has been found in all other organs, such as the brain or thoracic cavity (Horne and Missmer, 2022). Endometriosis is thought to affect about 1 in 10 of those who are female at birth and, although symptoms often emerge during adolescence, it generally takes years and multiple visits to the GP and specialists before a diagnosis is made (Horne and Missmer, 2022). The cause of endometriosis is unknown, but is likely involve a combination of genetic, immune system and environmental factors.
Both IBS and endometriosis can cause a variety of symptoms, including abdominal pain, bloating, diarrhoea and/or constipation. Although not all women with endometriosis have gastrointestinal symptoms, many do, and it is common for affected women to initially receive a diagnosis of IBS, and then sometimes years later to be diagnosed in addition with endometriosis. Symptoms specific to endometriosis are significant and include chronic pelvic pain, dysmenorrhoea, dyspareunia and fatigue, and it may potentially contribute to subfertility or infertility (Horne and Missmer, 2022).
Given the symptom overlap between the two conditions, it is imperative that clinicians consider endometriosis in menstruating females who present with IBS-type symptoms.
Diagnosis
Both IBS and endometriosis can be challenging to diagnose. Diagnosis is based on a combination of medical history, physical examination and imaging.
IBS
IBS should be considered as potential diagnosis if an individual reports that they have had abdominal pain or discomfort, bloating and changes in bowel habits for at least 6 months (National Institute for Health and Care Excellence (NICE), 2017). Red flags such as unintentional weight loss, rectal bleeding, family history of bowel or ovarian cancer, and symptom commencement after the age of 60 years should be ruled out. Further investigation includes stool tests such as faecal calprotectin or faecal immunochemical stool tests, and blood tests (coeliac serology, full blood count, erythrocyte sedimentation rate, C-reactive protein). As per NICE (2017) guidelines, further investigations are not necessary if individuals meet the criteria for IBS diagnosis.
Endometriosis
The gold standard for the diagnosis of endometriosis remains laparoscopic surgery. Less invasive imaging techniques can be used; however, the absence of endometriosis on various imaging techniques does not rule it out (Horne and Missmer, 2022). There is increased demand to find better diagnostics but various potential biomarkers have so far been found to be unreliable. On average, it takes 8 years for a diagnosis of endometriosis to be made in the UK, a delay that has not improved significantly over the past two decades (Ghai et al, 2020). For individuals to be diagnosed, multiple visits to GPs and even gynaecologists are often necessary before endometriosis is correctly identified (Pugsley and Ballard, 2007).
Management of IBS
Dietary and lifestyle advice
Once an IBS diagnosis has been made, health professionals should emphasise the importance self-help strategies for patients to manage the condition. The discussion can also include stress reduction and relaxation, and increasing physical activity.
In terms of nutritional management, NICE (2017) guidelines offer the following general dietary strategies:
- Eating regularly and taking time to eat
- Avoiding skipping meals or leaving long gaps between meals
- Drinking at least 8 cups of non-caffeinated fluids a day
- Reducing tea and coffee consumption to three cups a day
- Reducing consumption of alcohol and fizzy drinks
- Limiting certain high-fibre foods
- Reducing intake of resistant starches. These include unprocessed grains, legumes, green bananas and cooked, cooled potatoes or rice. However, it needs to be noted that many of these foods also have a variety of health benefits
- Limiting overall fruit to three portions a day
- Avoiding sorbitol, which is found in sugar-free sweets, if diarrhoea is the predominant symptom
- Adding oats or up to 1 tablespoon of linseeds may be helpful for those who have bloating or excess flatulence.
These simple changes may be sufficient for some individuals to significantly improve their bowel habits and can be encouraged by health professionals, such as GPs and nurses.
Next steps
If the above strategies are not sufficient to improve IBS symptoms, individuals can be referred to dietitians for consideration of exclusion diets, such as the low FODMAP diet, or more specialised interventions. Information on the low FODMAP diet (see below) should only be given by health professionals with the expertise and additional training in the area.
FODMAP is an acronym and stands for fermentable oligosaccharides, disaccharides, monosaccharides and polyols, which are groups of short-chain carbohydrates found naturally in foods such as certain fruit and vegetables (ie apples, pears, onion and garlic), grains (ie wheat and barley), legumes and milk products. FODMAPs are digested poorly in the small intestine and continue to the large intestine. Two processes occur in the large intestine. First, certain FODMAPs are osmotic, drawing water into the large intestine and increasing pressure, and, second, they are fermented by the gut microbiota, which is a process that can create large volumes of gas.
Although FODMAPs are nutritious and beneficial for gut bacteria, in sensitive individuals they may contribute to IBS symptoms. The low FODMAP diet is a three-step approach that involves reducing foods containing these carbohydrates for 2–6 weeks and, once symptoms have improved sufficiently, different FODMAP groups are reintroduced one by one to test which ones may be triggering symptoms and at what portion size. The diet is then personalised for the individual, which involves all FODMAPs that were well tolerated to be brought back into the person's diet.
The low FODMAP diet is effective in 52-86% of individuals with IBS, and has superior outcomes compared with following the NICE guidelines cited above (Liu et al, 2020). A retrospective study found that 76% of patients in the low FODMAP group reported satisfaction with their symptoms compared with 54% of patients in the NICE group (Staudacher et al, 2011) However, several limitations of the diet have been raised. There is a potential risk of nutrient deficiency, namely calcium and fibre and a possible reduction in gut bacteria diversity; the diet is also confusing and restrictive for those with IBS, and long-term efficacy data are limited (Horne and Missmer, 2022).
Probiotics
The NICE (2017) guidelines mention that those who choose to try probiotics should be encouraged to try a product for at least 4 weeks. Two recent meta-analyses have concluded that certain combinations of probiotics, or certain strains, may potentially improve IBS symptoms; however, evidence for efficacy was low (Goodoory et al, 2023; Xie et al, 2023). Health professionals would need to provide specific strains or product recommendations for the best chance of desirable outcomes. However, side-effects were noted to be low, and therefore probiotics could be trialled by an individual after discussion with their health professionals, should they wish to do so (Goodoory et al, 2023).
Beyond food
The association and interaction between the central nervous system and enteric nervous system has been established, and it is well known that stress and anxiety can affect gastrointestinal motility and cause mucosal erosion. Strategies that modulate the gut–brain axis have been shown to have beneficial effects. For example, both gut-directed hypnotherapy and cognitive behavioural therapy has been shown to be beneficial in those suffering from IBS (Chaudhry et al, 2023). These strategies can be discussed with patients presenting with IBS, however, access within the public health system may vary.
Management of endometriosis
Whole-eating patterns
Although there is much interest in nutrition and its effect on endometriosis, the data are still fairly limited. There is currently not one single eating pattern that is promoted for individuals with endometriosis. Although the recently published European Society of Human Reproduction and Embryology (ESHRE) guidelines (ESHRE, 2022) includes a section on nutrition, it was concluded in the guidelines that no recommendations could be made at this stage, other than consideration the addition of omega 3 fatty acid supplements. The studies cited in the ESHRE (2022) guidelines were heterogenous and a meta-analysis was not possible (Becker et al, 2022). More research is needed, particularly well-designed studies that consider both nutritional factors that can reduce the risk of endometriosis and dietary patterns that may support those who have been diagnosed with the condition. For the purpose of this article, the focus is on practical applications that may improve the symptoms of endometriosis for those who have already been diagnosed with endometriosis. There is currently promising research in this area outlined below, but it is important to acknowledge the lack of high quality randomised controlled trials.
A systematic review by Nirgianakis et al (2022) has suggested that, based on available evidence, an eating pattern rich in antioxidants, polyunsaturated fatty acids and omega 3 fatty acids, in other words, foods that includes nutrients known to compose the Mediterranean diet, may improve general pain and dysmenorrhoea in those diagnosed with the condition. The Mediterranean diet has been well studied and there is strong evidence to suggest that this eating pattern is beneficial for preventing several chronic diseases and inflammatory processes – and, of course, it can be applied outside the Mediterranean area (Guasch-Ferré and Willett, 2021). The benefits may be due to the specific nutrients predominant in this diet, which may help reduce inflammation; this could potentially be the mechanism that helps reduce pain and dysmenorrhoea in individuals with endometriosis – and so merits further investigation. Good quality, randomised controlled trials would be necessary before a blanket recommendation could be made for all women with the condition. However, based on the limited available evidence, the Mediterranean diet could be recommended to individuals suffering from pain and dysmenorrhoea that are secondary to endometriosis who wish to consider changes to their dietary intake.
The principles of the Mediterranean diet are:
- An abundance of colourful fruits and vegetables every day
- Whole grains carbohydrates
- A daily intake of beans, legumes, nuts and seeds
- Regular consumption of seafood, especially oily fish
- Limiting red meat and poultry consumption to between low and moderate amounts
- Including more healthy fats, such as using extra virgin olive oil as the primary oil
- Daily intake of dairy products, if tolerated
- Limiting the intake of sweets and heavily processed foods.
However, it is important to take into account that adapting to this pattern of eating could be associated with increased cost and additional time to prepare suitable meals. Although the principles of the Mediterranean diet can be adapted to an individual's dietary, religious or cultural preferences, it may not work for everyone.
FODMAP and gluten-free diets
The low FODMAP diet previously discussed as a management strategy for IBS has also been investigated for those with endometriosis. A retrospective analysis of a cohort study of women attending an IBS service identified that, of the 160 women who met the Rome III criteria for IBS, 36% had concurrent endometriosis. All 160 participants had followed a low FODMAP diet for 4 weeks. The retrospective analysis found that 72% of those with concurrent endometriosis experienced a greater than 50% reduction in symptoms compared with 49% of those with no known endometriosis (Moore et al, 2017). Adherence to the diet was high in both the group with endometriosis and the control group.
This would seem to indicate that the low FODMAP diet may be an appropriate management strategy for those with endometriosis when gastrointestinal symptoms are present. However, it is important to consider that following the restriction phase of the low FODMAP diet should not be a long-term approach – the reintroduction and personalisation of the diet is therefore paramount. In addition, it should be taken into account that reducing consumption of high FODMAP foods may result in a reduction of consumption of foods that are particularly high in antioxidants, such as colourful fruit and vegetables.
In the author's experience, the reintroduction of previously poorly tolerated higher FODMAP foods is often possible after addressing symptoms using other strategies, such as modulating the gut-brain axis and adopting an overall anti-inflammatory eating pattern. Although there is no scientific evidence to support this approach, it is plausible that an anti-inflammatory eating pattern improves endometriosis-related symptoms such as pain and also reduces IBS-type gut symptoms in those with endometriosis, meaning that FODMAPs are overall better tolerated longer.
Therefore, it is essential that individuals have the support of a dietitian specialising in endometriosis before attempting the low FODMAP diet to ensure that, if certain foods or entire food groups are reduced over a longer term, there is a clear reason for doing so and that there is a definite indication that the individual benefits from this approach.
One retrospective before-and-after study (Marziali et al, 2012) examined a gluten-free diet in women with endometriosis. After 12 months, 75% of participants reported a reduction in dysmenorrhoea and an improvement in their quality of life. These results are encouraging. However, wheat contains both gluten and fructans (a FODMAP), and it is impossible to suggest whether a reduction in gluten or fructans can lead to symptom improvements; this is because, in general, a gluten-free diet also automatically reduces wheat-containing foods. Furthermore, participants may have changed their eating patterns after initiating a gluten-free diet as gluten is found in many packaged foods – this change could also have contributed to the reduction in symptoms.
Individuals suffering from endometriosis and gastrointestinal symptoms can trial a gluten-free diet should they wish to do so but, if gastrointestinal symptoms are present, coeliac disease should be excluded prior to initiation of the gluten-free diet. The support from a specialist health professional is strongly encouraged when making such adjustments in dietary intake.
Other key nutrients or foods Vitamin D
Several studies have examined the effect of vitamin D supplementation on endometriosis. A systematic review and meta-analysis of nine studies concluded that women with endometriosis had significantly lower vitamin D status than controls and that this had a negative correlation with severity of the symptoms (Qiu et al, 2020). However, the quality of individual studies was variable and the heterogeneity of the nine studies included in Qiu et al's (2020) meta-analysis was high.
Although universal vitamin D supplementation in people with endometriosis cannot yet be recommended, individual status should be assessed and corrected if a deficiency is identified (Nirgianakis et al, 2022). While some food sources, such as oily fish, red meat or egg yolks provide vitamin D, most vitamin D is produced by the body in response to sunlight on skin. In the UK, due to the position of the sun, it is impossible for the body to produce sufficient vitamin D and therefore supplementation is recommended between late September and April. The recommended amount in the UK is 400 iU (or 10 mcg) per day for all adults and children over the age of 1 year, although some individuals may need more or may benefit from supplementation throughout the year if they do not spend much time outdoors (NHS website, 2020).
Dairy
Dairy consumption is particularly controversial among many of those suffering from endometriosis. Some social media accounts promote strict exclusion of all dairy products, as these are wrongfully thought to be pro-inflammatory; however, research to date does not support these claims. Whole dairy products appear to be either neutral or potentially have an anti-inflammatory effect (Moosavian et al, 2020). A meta-analysis by Arab et al (2022) showed a reduction in the occurrence of endometriosis in those who consumed three or more servings of dairy foods (both low-fat and high-fat products) a day. On the other hand, palmitic acid, a type of fat found in meat and dairy foods, was associated with an increased risk of developing endometriosis as part of the Nurses' Health Study II (Missmer et al, 2010).
More research is required on the effect of dairy consumption among those with existing endometriosis and to determine whether the protective effects of dairy were due to calcium content or another nutrient found in dairy products. If individuals choose to avoid dairy for environmental or cultural reasons, due to lactose intolerance or their beliefs, they should be encouraged to consume calcium-enriched dairy alternatives. Calcium and vitamin D consumption has been associated with a reduction in primary dysmenorrhoea, although the review (Abdi et al, 2021) excluded those with known uterine pathologies such as endometriosis. In the case of lactose intolerance, small amounts of dairy are often still tolerated and not all dairy products need to be avoided.
Conclusion
IBS and endometriosis are complex disorders that can significantly impact on quality of life. Recognising the overlapping symptoms and distinguishing characteristics is crucial for accurate diagnosis and appropriate management. Nutrition and lifestyle interventions, tailored to each condition, play an important role in managing symptoms and improving overall wellbeing. Health professionals are encouraged to collaborate closely with registered dietitians to develop personalised interventions for individuals suffering from IBS or endometriosis. BJN
KEY POINTS
- Irritable bowel syndrome (IBS) and endometriosis are chronic conditions that cause pain and discomfort. Both conditions share symptoms, leading to potential misdiagnosis and delayed treatment
- Nutritional management for IBS focuses on self-help strategies, nutritional changes, and gut–brain axis modulation
- The low FODMAP diet can be effective, but requires expert supervision to avoid potential nutrient deficiencies and microbiota diversity reduction
- For endometriosis, a Mediterranean-style diet rich in antioxidants shows promise in alleviating pain and dysmenorrhoea. Interventions for gastrointestinal symptoms in those suffering from endometriosis should be personalised
CPD reflective questions
- How might the overlapping symptoms of irritable bowel syndrome and endometriosis impact the diagnostic process, and what steps can health professionals take to improve accurate identification of these conditions?
- Considering the nutritional management strategies outlined for both conditions, what challenges might individuals face in implementing these dietary changes, and how can healthcare providers offer effective support and guidance?
- In light of ongoing research on dietary patterns and their impact on endometriosis, how might future studies further refine and tailor nutritional recommendations for individuals diagnosed?