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The gut microbiome undergoes rapid and dramatic changes in species composition and gene expression when the host switches between eating cooked or raw vegetables, according to a team of scientists led by UC San Francisco and Harvard University. Their new study, published in Nature Microbiology, is the first to investigate how this aspect of diet affects the microbiome, and included experiments in both mice and humans.

The scientists also observed that mice lost weight during their stint eating raw vegetables (groups of animals were fed cooked and raw sweet potato, white potato, corn, peas, carrots, and beets), but when the microbiomes of these newly svelte mice were transplanted into other mice, the new hosts gained weight – an unexpected result that exemplifies how the interplay of gut microbes and host metabolism is complex, and requires further study. Interestingly, other experiments within the study showed that gut microbiomes change very little when switching from cooked and raw meat, although past research has revealed that cooking affects the nutrients and bioactive compounds in meat.

“‘Raw’ diets are becoming an increasingly popular dietary trend for certain health benefits as compared to a traditional diet with cooked food, and the differences in microbiome and metabolism demonstrated in this paper begin to shed light on some of the potential underlying mechanisms,” said co-author Katherine Louie, a scientist in Berkeley Lab’s Biosciences Area. Louie, alongside three other Berkeley Lab contributors, performed molecular analyses to determine how cooking affects the metabolites and phytochemicals present in vegetables and tubers.

More info: Read UC San Francisco’s full release