I came across some of the microbiome research in the recent years, I know about the hacker culture interest in fermented foods and do drink kefir semi-regularly

I came across some of the microbiome research in the recent years, I know about the hacker culture interest in fermented foods and do drink kefir semi-regularly myself. But there appears to be a quite some correlation between microbiome and, well, diet: https://www.nature.com/articles/nature12820 https://www.nature.com/articles/nature12820 Aparrantly you can change your microbiome rapidly by eating differently. When discovering effects for the whole organism, can’t it be that these are correlations that have been found before in nutrition studies? Why is / isn’t this a problem? Maybe I’m missing something.