Our digestive system is not just about processing food, our gut is home to an intricate ecosystem of microbes that play a critical role in our overall health, including our reproductive health. While many factors are outside our control regarding fertility, it is empowering to think that we can directly influence key components for a healthy pregnancy (i.e. egg and sperm health) through nutrition and a healthy gut. Importantly, this can be done without restrictive diets, numerous supplements, or expensive medical tests! Read on to learn why the gut plays a pivotal role in fertility, and how to build the foundations for a healthy pregnancy through nourishing this internal community. 

Gut health & Hormonal Health

The collection of this internal ecosystem is termed our gut microbiome (consisting of microbes such as bacteria, archaea, viruses and funghi). Co-existing with these microbes in a balanced state (symbiosis) is thought to be optimal for supporting our health. When functioning well, this internal community supports our fertility by enabling nutrient absorption, supporting a healthy immune system, dampening inflammation, and maintaining hormonal balance (1,2).While research investigating the link between the gut microbiome and fertility is still in its infancy, some exciting insights exist. Our gut bugs interact with our sex hormones in a bi-directional manner: Sex hormones (i.e. oestrogen, progesterone, testosterone) can affect our gut microbiome, and our gut microbiome can affect the production and regulation of our hormones. For example, the “oestrobolome” has been identified as a specialised group of gut microbes responsible for metabolising and regulating circulating oestrogen levels (3). This key sex hormone has various important roles within the body that directly affect fertility, supporting healthy menstrual cycles in females and sperm development in males, as well as indirect effects such as influencing libido, mood, and weight management (4,5).

‍Gut Microbiome & Fertility

‍So, what happens when the ecosystem becomes unbalanced?An unbalanced gut microbiome, termed dysbiosis, can occur via numerous means including upon prolonged antibiotic exposure, through a low-quality diet or following an illness. This deviation from a healthy gut microbiome is linked with many disease states including infectious diseases, metabolic disorders, and auto-immune diseases (2). Gut dysbiosis is also a common feature of conditions affecting female fertility including Polycystic Ovarian Syndrome (PCOS), and endometriosis, and is associated with low testosterone in males (6-8). An unbalanced gut microbiome can also affect the health of other microbial communities in the body, it has been suggested that gut dysbiosis could lead to vaginal dysbiosis which can affect fertility (9). While these associations are interesting, more research is needed to establish whether the gut microbiome plays a causal role in these conditions. (Is an unbalanced gut microbiome the reason why these conditions develop or is it simply a contributing factor?) Either way, looking at doing what we can to support and restore balance is beneficial.

‍How to Support Gut Health and Fertility

‍The biggest influence we have over the health of our gut microbiome is through our diet, because our microbes are reliant on what we feed them. Fibre to fuel fertility The key food source for our microbes is fibre. High-fibre plant foods travel down to our large intestine, mostly unabsorbed, where they feed our community of gut bugs. It’s been shown that diets higher in fibre are associated with a more diverse, healthy gut microbiome and a higher chance of pregnancy (10,11). In contrast, the typical “Western” style diet (lower in fibre and higher in added sugars and saturated fats) is associated with gut dysbiosis, poorer fertility and an increased risk of miscarriage (12,13).

Let’s explore key the sources of dietary fibre with evidence for supporting fertility…Fruits and vegetables – We all know that fruits and veggies are important for our general health, but there’s also strong evidence to show they have a beneficial effect on fertility for women and men (14).  While 5-a-day is a good place to start, aiming to increase your intake above this to include a colourful range (think eat the rainbow) will increase your intake of beneficial fibres, nutrients, and antioxidants to support fertility.
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Wholegrains – When it comes to carbohydrates, quality is key. Choosing wholegrains (wholemeal bread / pasta, brown or wild rice, buckwheat, bulgur, quinoa, rolled oats, whole rye, etc.) over refined grains is a great way to add fibre, along with important vitamins, minerals and antioxidants to the diet. Higher wholegrain intake has been shown to lower levels of inflammation (15) and regulate glucose metabolism (16), two key mechanisms involved in improving fertility outcomes, and has been associated with improved outcomes through IVF (17).

Nuts and seeds – Full of dietary fibres, healthy fats, vitamins and minerals; nuts and seeds are a key part of a healthy preconception diet. Including 2 servings of nuts a day is associated with positive effects on fertility outcomes (18). Due to the varying nutritional profiles, it’s advisable to include a diverse range of different nuts and seeds to gain full benefit.

Beans & legumes  - While animal proteins can have a place in a healthy, balanced preconception diet, a higher intake of plant-based proteins is associated with improved fertility. Replacing animal proteins with plant-based proteins has been shown to promote healthy ovulation in females  (19), and reducing processed and fatty meats has been shown to improve sperm parameters in males (20). Beans and legumes are an excellent source of plant-based protein, known to be a hit with our gut microbiome due to their high fibre content. They are also packed full of important vitamins and minerals. If you’re new to beans and legumes, add them into the diet gradually to allow time for the gut to adapt to the increase in fibre.The Mediterranean Diet The Mediterranean diet has the most consistent and robust evidence for improved fertility outcomes in women and men (21). The dietary pattern is based on high-fibre foods including plenty of fruits, veggies, wholegrains, beans, legumes, nuts and seeds. It is also includes lean proteins, moderate dairy and unsaturated fats.

Omega-3 fats, found predominantly in oily fish (salmon, sardines, mackerel, herring, trout, etc.) are of particular importance due to their anti-inflammatory effects and vital role in early foetus development. While not part of the fibre family, omega-3 fats have also been shown to positively affect the gut microbiome. It’s advisable to include 1-2 pieces of oily fish a week or consider supplementation. 

‍Build Healthy Foundations

‍Taking positive changes to optimise your nutrition and gut health is beneficial at all stages of life, but even more important when trying to conceive as you’re also influencing the health of the future generation. The health of eggs and sperm can be impacted by diet in the 3 months prior to release, so optimising your nutrition during this pre-conception phase influences the future health of the baby. The fertility journey can be stressful and overwhelming, and nutrition should not be an added complication. By looking at simple ways to nourish your gut with a fibre-rich diet, you can take control of your gut health, support your fertility and start to build the foundations for a healthy pregnancy. If you would like personalised support, get in touch with Jessica Neil, Sanno gut health & fertility clinician. 

Written by nutritionist Jessica Neil, December 2024.

References:
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