The researchers examined the impact of cooking food on the microbiomes of mice after feeding them with different diets. Each of the four groups of rodents had a different diet: raw meat, cooked meat, raw sweet potatoes or cooked sweet potatoes.
It turned out that raw meat, compared to cooked meat, had no discernible effect on the animal's gut microbes.
In contrast, raw and cooked sweet potatoes significantly altered the composition of the microbiomes of the animals, as well as the patterns of genetic activity of the microbes and the biologically crucial metabolic products they produced.
Microbiologists confirmed their conclusions with another experiment, where they had used a more diverse variety of vegetables. That time they fed the mice with sweet potatoes, white potatoes, corn, peas, carrots and beets, both raw and cooked.
Why does cooking alter the microbiome?
The researchers attributed the microbial changes they saw to two key factors. FirstCooked foods allow the host to absorb more calories in the small intestine, leaving less for hungry microbes lower in the intestine.
He second factor is that raw foods contain potent antimicrobial compounds that appear to directly damage certain microbes.
"We were surprised to see that the differences were not only due to changes in carbohydrate metabolism, but could also be due to the chemicals found in plants," said Peter Turnbaugh, one of the study's authors.
And the microbiota of humans?
To understand if similar microbial changes could be recorded in humans, Turnbaugh's team conducted an experiment with a small group of volunteers.
A professional chef prepared appetizing raw and cooked menus for a small group of participants. They tried each diet for three days.
The analysis of their microbiomes showed that these different diets significantly affected.
"It was exciting to see that the impact of the kitchen we see on rodents is also relevant for humans, although interestingly, the details of how the microbiome was affected differ between the two species," Turnbaugh said.
He also added the need for future research to understand the impact of long-term dietary changes.
The study also raises questions about how microbes associated with humans have evolved over the millennia to adapt to our culinary culture, and if this could have important side effects for modern health.
The study was published in the journal Nature Microbiology.