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Are There Differences Between Male and Female Gut Microbial Communities?

Are there differences between male and female gut microbiomes? (NOTE: gut microbiome is the community of microbes living in the gut.) I always thought YES, based on that there seem to be so many biological differences between males and females. But according to this blog entry from uBiome (a microbiome sequencing service which has analyzed thousands of gut microbiomes - the microbes living in the gut ) there aren't. They only looked at gut microbiomes (by analyzing fecal samples), and not at other body sites in this comparison. Other past studies have found  that other body sites have bacteria differences. Even the comments after the post were interesting. From the uBiome Blog:

A Surprising Comparison of Male vs. Female Microbiomes

I must admit, I was curious. So I went over to the desk of our brilliant Lead Data Scientist, Dr. Siavosh Rezvan-Behbahani, to find out. Could you look at all of uBiome’s gut samples, I asked, and see what the difference in microbiome composition is between men and women? And the corollary, is it possible to predict from microbiomial data whether the person giving the sample was male or female? With human DNA, of course you can determine gender based on the chromosome signature XX vs. XY. But does the microbiome have a gender signature too?

Siavosh dove in. He spent many hours analyzing, plotting numbers, running different machine learning classifier algorithms. He looked at healthy male and female samples in part of our dataset, all the way down to genus level. And here’s what he found, which blew my mind.

It turns out that in our dataset, there is no statistically significant difference between male microbiomes and female microbiomes. And, given a random sample, we would not be able to determine if it came from a man or a woman.

This result is fascinating to me, because it suggests that maybe men and women aren’t that different in some ways. We all have two eyes, and belly buttons, and similar proportions of bacteria swimming around inside our intestines.

(Of course there’s the standard disclaimer that this is just what we observe in our gut dataset, and may not be representative of the entire human population. It’s also possible that there is a difference but it’s much more subtle than we expect. In any case, this result is encouraging me to think up other questions to ask!)