Probiotics are live microbes that provide health benefits, primarily through their positive effect on our gut microbiome. Let’s suppose we think of our gut microbiome as a densely populated internal ecosystem, like you would observe in a rainforest. Species coexist, feed off each other, and depend on each other for survival. As in the wild, diversity leads to the health of the ecosystem. Probiotics introduce new beneficial microbes into this environment, like new seeds to support a thriving forest. 

These microbes can be found naturally in some fermented foods and are also available in supplements (capsules, powders, liquids and other forms). When considering whether to take a probiotic supplement it is important to consider the evidence for the exact strain, dose, and the condition or symptoms it is targeting. Like medications, probiotics should only be considered in specific circumstances. 

Should I take a supplement to support my gut health?
‍
There is no evidence to suggest that taking a general probiotic is beneficial to gut-health in healthy individuals, and can sometimes cause adverse symptoms (e.g., bloating). Unless you have a specific health issue where a targeted probiotic may be helpful, the best way to support your gut health is through eating a fibre-rich diet full of a diverse range of fruits, vegetables, beans, legumes, nuts and seeds. 
‍
What about fermented foods?

Fermentation is an ancient technique of preserving food, occurring when bacteria and yeast ‘pre-digest’ food and drink, producing a range of vitamins, and compounds and promoting the growth of beneficial bacteria. Common fermented foods today include live yogurt, kefir, kombucha, sauerkraut, and kimchi. There is currently very little research on fermented foods and fertility outcomes specifically. However, there is some evidence to show positive health effects, with the strongest evidence in association with fermented dairy. Benefits are seen across digestive health, heart health, bone health, weight management, and immunity (1). By supporting general health and increasing the availability of beneficial nutrients, fermented foods can be considered a positive addition to a healthy pre-conception diet.
‍
Should I take a supplement to support my fertility?

An unbalanced gut microbiome (dysbiosis) has been observed in association with conditions affecting female fertility including Polycystic Ovarian Syndrome (PCOS), and endometriosis, and is associated with low testosterone in males (2-4). Vaginal dysbiosis (an imbalance in the vaginal bacterial community) is linked with infertility and preterm birth (5). A balanced gut and vaginal microbiome are important to support fertility and a healthy pregnancy, with the maternal microbiome shaping the baby’s microbiome, via direct transfer of bacteria (6). A beneficial link has been found between probiotics and fertility. However, more research is needed to understand exactly what strains and doses are most effective in each situation.

There is evidence to show that probiotics can support fertility by (7-9): Balancing the vaginal microbial community Decreasing inflammation, improving blood sugar control, and balancing testosterone levels in women with PCOS Improving sperm concentration and motility in menWhile we await further research to establish clear protocols for the use of probiotics for reproductive health, taking a probiotic with the lactobacillus strain may help support fertility outcomes in some situations. Importantly, everyone can support their fertility by nourishing their gut health through their diet. (For more information check out our Fertility & Gut Health blog here).

We live in a symbiotic relationship with the trillions of microorganisms living both in us and on us, and their health is essential for our health. Our largest community of microbes live in our digestive tract, and we can directly influence their health through what we feed them. A healthy pre-conception diet based on whole plant foods (i.e., fruits, vegetables, wholegrains, beans, legumes, nuts and seeds) plus considering adding some fermented foods, supports our gut health and provides a range of beneficial nutrients required for a healthy pregnancy. In some situations, a probiotic containing lactobacillus may be beneficial but more research is required to clarify protocols for use.

If you would like personalised support, get in touch with Jessica Neil, gut health & fertility clinician you will find on the SANNO platform.

Written by nutritionist Jessica Neil, July 2025.

References:
1. Şanlier, N., et al. (2019). "Health benefits of fermented foods." Critical reviews in food science and nutrition 59(3): 506-527.
2. Torres, P. J., et al. (2018). "Gut Microbial Diversity in Women With Polycystic Ovary Syndrome Correlates With Hyperandrogenism." J Clin Endocrinol Metab 103(4): 1502-1511.
3. Qin, R., et al. (2022). "The gut microbiota and endometriosis: From pathogenesis to diagnosis and treatment." Front Cell Infect Microbiol 12: 1069557.
4. Liu, S., et al. (2022). "Correlation between gut microbiota and testosterone in male patients with type 2 diabetes mellitus." Frontiers in Endocrinology 13: 836485.
5. García-Velasco, J. A., et al. (2017). "What fertility specialists should know about the vaginal microbiome: a review." Reproductive biomedicine online 35(1): 103-112.
6. Mady, E. A., et al. (2023). "Impact of the mother's gut microbiota on infant microbiome and brain development." Neurosci Biobehav Rev 150: 105195.
7. López-Moreno, A. and M. Aguilera (2020). "Probiotics Dietary Supplementation for Modulating Endocrine and Fertility Microbiota Dysbiosis." Nutrients 12(3).
8. Cozzolino, M., et al. (2020). "Therapy with probiotics and synbiotics for polycystic ovarian syndrome: a systematic review and meta-analysis." Eur J Nutr 59(7): 2841-2856.
9. Helli, B., et al. (2022). "Probiotic effects on sperm parameters, oxidative stress index, inflammatory factors and sex hormones in infertile men." Hum Fertil (Camb) 25(3): 499-507.
‍