In an Atlantic article published yesterday, the 28th of April, Ed Yong discusses the findings of two large studies, one Dutch, the other Belgian, comparing the gut microbiomes of individuals. The Dutch study looked at stool samples of 1,135 people, the Belgian, 1,106.
http://www.theatlantic.com/science/archive/2016/04/why-are-your-gut-microbes-different-from-mine/480207/Both looked at how hundreds of factors affect the microbiome, including age, height, weight, sleep, medical history, smoking, allergies, blood levels of various molecules, and a long list of foods. Both found dozens of factors that affect either the overall diversity of microbial species, or the abundance of particular ones. And encouragingly, their respective lists overlap considerably.
But here’s the important thing: Collectively, the factors they identified explain a tiny proportion of the variation between people’s microbiomes—19 percent in the Dutch study, and just 8 percent in the Belgian. Which means we’re still largely in the dark about what makes my microbiome different from yours, let alone whether one is healthier than the other.
“With all the knowledge we’ve gathered, we made the best possible effort to capture all the factors we could imagine, and we could only explain 8 percent of the total variation,” says Jeroen Raes from the University of Leuven, who led the Belgian study. “It’s very humbling.”