The gut microbiota differs from one individual to another and this may partly explain a person’s susceptibility to certain diseases, like colorectal cancer or diabetes. However, it is still unclear what personal factors influence the gut microbiota’s composition. The authors of the aforementioned study have found that sex plays an important role, with their research showing that women have significantly different gut microbiota composition overall and particularly lower Bacteroidetes abundance compared to men. They reached this conclusion after analysing faecal samples from 82 individuals and sequencing the genes found in the samples’ bacteria.
The relationship between sex and gut bacterial composition may be mediated by sex steroid levels. These have been found in a previous study to have an impact on gut microbiota. For this reason, the researchers also looked at the effect of adiposity (which alters sex steroid levels), fibre intake, which influences estrogen levels. The authors argue that sex, body mass and dietary fibre intake may operate through similar mechanisms – including hormone mediated pathways – to modulate the human gut microbiota.
The role of sex had previously been explored, but while in animal models some differences arose between females and males’ gut microbiota, analyses of human data have remained inconclusive.
The authors of the latest study point out that their results may be updated when a more varied sample of volunteers is analysed (as those involved in the study were mostly white Americans) and more complex interactions are taken into account – for example, a diet rich in fibre may be a marker of a healthy lifestyle in general. However, the paper’s authors say, “There is increasing evidence of a relationship between gut microbiota and gastrointestinal diseases, including colorectal cancer and other diseases, such as diabetes.” They conclude, “Our findings suggest that sex, BMI, and dietary fibre contribute to shaping the gut microbiome in humans. Better understanding of these relationships may have significant implications for gastrointestinal health and disease prevention.”