Written by Laura Freeman
In a time when we are striving for equality amongst all sexes and non-binary individuals (as we rightly should), it’s equally interesting to consider how we are all different.
In the following text, the terms male and female will be used in the context of biological and chromosomal differences and the importance of gender preferences and identities are addressed briefly at the end.
When it comes down to our gut microbes, there’s emerging evidence demonstrating important variations between males and females. This is the microgenderdome – the term used to describe the sex-related differences in our microbiomes and how they interact with sex hormones and immune systems. This is important because there are often significant differences in how some diseases affect women more than men and vice versa. For example, Irritable Bowel Syndrome and autoimmune diseases are much more common in females. We also know that men and women exhibit sex-specific responses to the exact same diet (1), something that is both fascinating and important when we are discussing gut health and the importance of the community of microbes involved.
In the early days of research, sex differences were largely ignored and research studies do not always represent the different sexes equally. However, more data is starting to come through and will hopefully help us to understand these differences more clearly. With new knowledge about the microgenderdome, we can work towards more specific and personalised approaches, diagnoses and treatments – especially for those conditions that are related to the digestive and connected systems.
What has the research shown us so far?
Like a lot of research, much of it has been conflicting but there is enough to show that sex-related differences help with the predictability, maturity and diversity of our microbiomes.
Whilst many differences in our microbiome are inexplicable, being male or female does seem to provide reliable and important information about different gut microbes. Men and women have been shown to have very distinct microbiome patterns populating the gut (2) and it turns out that these sex-related differences are one of the most predictable differences that exist.
It is generally accepted that females tend to mature faster than males. So it is fascinating to see this maturity is also observed in the gut – the female microbiome does appear to mature earlier than the male microbiome. It is also interesting to consider this in parallel with other research which suggests that in children, females tend to optimise brain connections earlier than males (3) . It would be plausible then, to consider that the gut-brain axis plays an important a role here though more specific research is needed.
Diversity in the gut microbiome is a positive thing, it is what we should be striving for as it can lower your risk of disease and strengthen your immune system. Some research suggests that the female microbiome is more diverse than a male’s, though this diversity does seem to become less pronounced as we age with plateaus being observed in both sexes by approximately 40 years of age.
However, these findings were not always universal and some inconsistencies were shown across different populations, amongst the Chinese cohorts in one instance (4). The reasons for this were not discernible in this study, showing that further research is needed to uncover novel patterns and further insights on the matter.
What does it all come down to?
A two-way street between the microbiome, sex hormones and our immune systems.
It seems that the main driver for these differences are hormones. The effect of this has been cleverly shown in studies which looked at same sex and opposite sex twins before and after puberty. Very clear differences were seen between opposite sex twins after puberty, a time in our lives when hormone changes are in full force. From this, studies have suggested oestrogen and testosterone have important effects on the gut microbiome.
The differences between male and female immune systems are well recognised. In fact, most of our immune cells have receptors specifically for our sex hormones. We know our gut microbiota interacts with our immune system on many different levels and sex hormones play a role. This may in part explain why autoimmune diseases are more common amongst women (5).
Our gut microbiota are affected by drugs and males and females have different patterns in medication use. This could be a very logical contributing factor as to why there are sex differences in the microbiome. For example, males are more likely to take heart medication while women are commonly prescribed the oral contraceptive pill, laxatives and antibiotics, all of which affect the microbiome in different ways (6/7).
Battle of the sexes
There is room for much more research to be done in this area so that we understand more about the microbiome and how and why different sexes influences it. Future research should also take into account how socially constructed roles, behaviours and the personalities of girls, women, boys, men and non-binary individuals affect our gut microbiota too. All this being said, it seems that with the current evidence, the battle of the microbiome sexes has no winner, neither the male or female microbiome seem to have an advantage over the other. So although we have no control over our chromosomes, we do have control over our microbiomes.
Luckily, we are able to change both our diet and lifestyles, both which influence it and that is a really helpful thing for our gut microbiota!
About the author
Dr Laura Freeman obtained her Medical Degree from the University of Edinburgh in 2006. Both within and outside of her General Practice, Dr Freeman has developed a strong interest for plant based nutrition and optimising health through lifestyle choices. In 2019, Dr Freeman became a diplomat of the International Board for Lifestyle Medicine. Her focus is putting her passion in Lifestyle Medicine into practice for her patients and watching the incredible success of their lifestyle interventions.
- 1 Moschen AR, Wieser V, Tilg H. Dietary Factors: Major Regulators of the Gut’s Microbiota. Gut Liver. 2012;6:411–416. pmid:23170142.
- 2 Jašarević E, Morrison K, Bale T. 2016. Sex differences in the gut-microbiome-brain axis across the lifespan. Philosophical Transactions of the Royal Society B. 371(1688)
- 3 Preferential Detachment During Human Brain Development: Age- and Sex-Specific Structural Connectivity in Diffusion Tensor Imaging (DTI) Data. Sol Lim; Cheol E. Han; Peter J. Uhlhaas; Marcus Kaiser.Cerebral Cortex 2013; doi: 10.1093/cercor/bht333
- 4 Jacubo de la Cuesta-Zuluaga et al. Age- and Sex-Dependent Patterns of Gut Microbial Diversity in Human Adults. American Society for Microbiology. 2019; 4.
- 5 Fransen, F, van Beek, AA, Borghuis, T. The impact of gut microbiota on genderspecific differences in immunity. Front Immunol. 2017;8:754.
- 6 Maier L, Pruteanu M, Kuhn M, Zeller G, Telzerow A, Anderson EE, et al. Extensive impact of non-antibiotic drugs on human gut bacteria. Nature 2018;555:623–628
- 7 Sinha T, Vich Vila A, Garmaeva S, Jankipersadsing SA, Imhann F, Collij V, et al. Analysis of 1135 gut metagenomes identifies sex-specific resistome profiles. Gut Microbes 2019;10:358–366