This @Nature paper on sugar & the gut microbiome is pretty crazy: It is known that the gut microbiome (the bacteria living in the gut) has a powerful effect on health & disease, especially via immune modulation. But one reason why this field has remained in a “hypothesis” state for so long is that, for all practical purposes, it’s almost impossible to rigorously connect the composition of the food a person eats with the composition of their gut microbiome and further to outcomes. This is because nobody actually checks everything a person eats, and people are notoriously bad at self-reporting the food they consume. This paper actually did this! It looked at 9,419 food items consumed by 173 hospital patients undergoing allogeneic haematopoietic cell transplantation during a course of antibiotics. In this therapy, donor-derived blood-forming stem cells are used to rebuild a recipient’s blood and immune system to treat blood cancers. Then they linked this to gut microbiome composition derived from repeated stool measurements. Antibiotics are known to disrupt the gut microbiome, which can also facilitate resistance. So the links between all these (allo-HCT, antibiotics, gut microbiome, diet) are probably quite complex. The paper is overall quite interesting, but essentially what it found was that, on antibiotics, the gut microbiome diversity was reduced if sugar was consumed vs no sugar. Outside antibiotic treatment, there was no change. These are of course correlations and not causality, but it’s nevertheless impressive the rigor and level of depth with which this study was done.