Our gut starts at our mouth and encompasses the whole of our digestive tract including our stomach, intestines and colon. As well as being responsible for the breakdown and absorption of the food we eat, it is also home to trillions of microorganisms and bacteria which make up our gut microbiome. Our gut is responsible for much more than just our digestive health, there are links between the gut and the brain, the immune system and the cardiovascular system, meaning the wellbeing of our gut and its microbiome can potentially affect many other aspects of our health, including fertility.
Leaky gut syndrome and fertility: is it a thing?
‘Leaky gut syndrome’ is a proposed condition where it is said that gaps appear between the cells lining your gut allowing toxins and other substances to leak into the surrounding tissue producing inflammation. Some health practitioners claim this is the cause of a wide range of long-term conditions, including infertility (1). Currently however there is a lack of scientific evidence to support the concept that the gut can become ‘leaky’ or, in scientific terms, more permeable, to the extent that it can be the cause of medical conditions. While some studies have linked a higher prevalence of intestinal permeability in women with issues of infertility such as recurrent pregnancy loss (2) no studies have linked this to being the cause and it may just be a symptom of that situation.
Gut health, weight & fertility
Women of a higher weight are at increased risk of reproductive problems, which may in part be due to poor egg quality because of increased exposure to oxidative stress and inflammation. We know that what we eat can change the function of our gut microbes and excess intake of calories, processed meat, high levels of sugar and salt, along with little to no fibre, has the potential to negatively affect our gut microbiome. People with obesity and chronic inflammation have been found to have an imbalance in their gut microbiome in comparison to people without these conditions. Recently, a study in mice has shown that a high fat diet can induce gut microbiome imbalance and ovarian inflammation through changes in gene expression providing preliminary evidence for a link between an obesogenic diet, gut health and infertility (3,4).
Gut health & PCOS
Major characteristics of PCOS include insulin resistance and hyperandrogenism. The consequences of this include compromised fertility, along with being at a higher risk of developing cardiovascular disease and Type 2 diabetes. Interestingly, studies have found that the gut microbiome of women with PCOS is different to those without the condition (5) and recent research now suggests that a gut microbiome imbalance may drive the development of both PCOS and insulin resistance (6,7)
Gut health & reproductive hormones
The bacteria in our gut play a role in the breakdown of oestrogen through the action of the enzyme β-glucuronidase. Alterations in gut microbiome diversity can reduce or increase the activity of this enzyme resulting in lower or higher levels of oestrogen (8) leading to disruptions in the menstrual cycle, irregular periods, impaired ovulation, PCOS and endometriosis, ultimately affecting fertility success.
How can we promote gut health?
- Aim to consume 30g of fibre a day along with prebiotic foods. Fibre is found in whole grains, legumes, vegetables, fruit, nuts and seeds. Prebiotics, not to be confused with probiotics, are foods that feed our good bacteria and have been shown to result in specific changes in the composition and/or activity of the gut microbiota conferring a benefit to the person. Many forms of dietary fibre act as prebiotics such as apricots, nectarine, watermelon, artichokes, asparagus, brussel sprouts, garlic, almonds, barley, hazelnuts and legumes. Incorporating these fibres in your diet has the potential to improve the balance of the gut microbiome and the success of pregnancy in females with infertility (9).
- Incorporating probiotic foods, which contain live microorganisms into the diet such as kefir and natural yoghurt has the potential to populate the gut with beneficial bacteria rebalancing the gut microbiome and promoting diversity.
What about probiotics?
Probiotics are live bacteria and yeasts, which when taken and reach our gut alive, have the potential to restore the balance of our gut microbiota by increasing the number of ‘good’ or ‘friendly’ bacteria. But beware that not all products that claim to be a probiotic may reach the gut alive. A lot of research is underway to understand whether probiotics could have a positive role in fertility disorders and for hormonal imbalances. We now know that an altered vaginal microbiome may influence fertility (10) and studies have found that oral probiotic supplementation with two Lactobacillus strains can restore a healthy vaginal flora in up to 82% of women with previous vaginal microbiome imbalance (11,12). While there is preliminary evidence that probiotics could help with issues of fertility, more research is required to determine what specific gut bacterial species play helpful or harmful roles in conditions of infertility and this will help to determine what specific probiotics have the potential to benefit specific conditions (13).
Prioritising gut health could positively influence both reproductive and overall health however the precise link between gut microbiome and fertility remains unclear. Basing your diet on whole grains, fruit, vegetables, nuts, seeds, lean protein, favouring unsaturated fats, whilst limiting foods that can promote gut imbalance and inflammation such as high-fat, high-sugar foods and alcohol is the best route to a healthy gut.
- “Leaky gut syndrome” - NHS [Internet]. [cited 2020 Oct 27]. Available from: https://www.nhs.uk/conditions/leaky-gut-syndrome/
- Tersigni C, D’Ippolito S, Di Nicuolo F, Marana R, Valenza V, Masciullo V, et al. Recurrent pregnancy loss is associated to leaky gut: A novel pathogenic model of endometrium inflammation? J Transl Med [Internet]. 2018 Apr 17 [cited 2020 Oct 2];16(1). Available from: https://pubmed.ncbi.nlm.nih.gov/29665864/
- Davis JS. Connecting female infertility to obesity, inflammation, and maternal gut dysbiosis [Internet]. Vol. 157, Endocrinology. Endocrine Society; 2016 [cited 2020 Oct 2]. p. 1725–7. Available from: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6285284/
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