Raw versus cooked meat had no discernible effect on the animals' gut microbes. In contrast, raw and cooked sweet potatoes significantly altered the composition of the animals' microbiomes, as well as microbes' patterns of gene activity and the biologically crucial metabolic products they produced. The group attributed the microbial changes they saw to two key factors: cooked food allows the host to soak up more calories in the small intestine, leaving less for hungry microbes further down the gut; on the other hand, many raw foods contain potent antimicrobial compounds that appear to directly damage certain microbes.