Cooking foods affects the microbiome. The study recently published in Nature Microbiology shows the effects of eating raw or cooked foods on the gut microbial community. (1)
Food cooking and the microbiome
The researchers fed the guinea pigs (rats) the same raw and cooked foods. While the impact on the microbiome was similar with meat, a significant difference emerged with starchy foods.
Indeed, the low digestibility of some high-starch foods when consumed raw (e.g., sweet potato and white potato) corresponds to significant – and negative – changes in the structure of the gut microbial community.
The role of starches
Cooked foods rich in starch are easily digested and mostly absorbed in the small intestine (thus, processed by host enzymes). Should they be consumed raw instead, they reach the colon and produce the same detrimental effects on microbes observed in antibiotic-treated mice. (2)
Conversely, foods with low starch content (carrot and beet) as well as foods with high amounts of highly digestible starch when raw (corn and peas) resulted in almost negligible changes in gut microbes.
The evidence on humans
The impact of raw and cooked foods on the gut microbiome was also evaluated on a small group of healthy volunteers. With evidence consistent with findings in the guinea pig study.
In subjects fed cooked tubers, favorable changes in the microbiota were observed within 48 h after the start of the diet and over the following 5 days. In contrast, the group of volunteers fed raw tubers showed a delayed (72 hours later) and less lasting (up to 24 hours) change in the microbiota.
Notes
(1) Carmody, R.N., Bisanz, J.E., Bowen, B.P. et al. (2019) Cooking shapes the structure and function of the gut microbiome. Nature Microbiology, https://doi.org/10.1038/s41564-019-0569-4
Professional journalist since January 1995, he has worked for newspapers (Il Messaggero, Paese Sera, La Stampa) and periodicals (NumeroUno, Il Salvagente). She is the author of journalistic surveys on food, she has published the book "Reading labels to know what we eat".
