Cooked versus raw food: which is better for a healthier gut
A wise man once said “you become what you eat”. Now, 17 scientists — and a professional chef — at the University of California San Francisco (UC San Francisco) and Harvard University say that how you eat your food — cooked or raw — matters, too.
In a recent study, the scientists looked at the impact of eating cooked versus raw food on gut bacteria. Good gut bacteria help to fight inflammation, control weight and even prevent diseases like some cancers, research shows.
They published their research in the peer-reviewed journal Nature Microbiology on 30 September, in the article “Cooking shapes the structure and function of the gut microbiome”.
While a lot of research has been done on the impact of different gut microbes on human health — starting from its effects on constipation and chronic inflammation to weight gain — nobody had yet researched how cooking our food changes the gut flora.
To summarise the seven-year research: yes, cooking changes our gut bacteria in several ways. But we need more research to show how it affects weight gain and weight loss.
For example, eating raw food (including raw meat) led to weight-loss in the mice this study. But transferring their gut bacteria in mice on a cooked-food diet didn’t have the same effect.
The research at UC San Francisco and Harvard also led to two key conclusions: eating cooked food increases its absorption in the small intestine, leaving little food for the good bacteria in the large intestine – which then starve and die. But many raw foods contain antimicrobials that kill gut bacteria – good as well as bad.
The researchers at UC San Francisco and Harvard first experimented with mice – feeding one group of mice raw sweet potato and another group of mice cooked sweet potato.
Surprisingly, they saw a notable difference in the kind of bacteria that thrived on cooked versus raw meals, the gene activity of the bacterial colonies as well as the metabolic products produced by bacteria.
The researchers also tried feeding the mice raw versus cooked meat as well as other veggies like white potato, corn, peas, carrots and beets – but this time they didn’t find a significant difference in the gut microbes.
Analysing the results – they gave two important reasons for the significant change in the microbial colony:
• Cooked food is absorbed easily through the small intestine, leaving the microbes residing in large intestine devoid of essential nutrition. Therefore, their diversity and number go down.
• Several raw foods naturally have strong antimicrobial substances that are responsible for killing off specific types of gut microbes.
Peter J. Turnbaugh, the corresponding author of the study, told the media: “the differences were not only due to changing carbohydrate metabolism but also may be driven by the chemicals found in plants”.
Simply put, cooking alters the food itself – it changes the chemicals in the plants. Additionally, eating cooked versus raw food promotes the growth of different bacteria in the gut. And the different bacteria have different ways of breaking down sugars.
Turnbaugh is associated with the Department of Microbiology and Immunology, at UC San Francisco, and the Center for Systems Biology, Harvard University in Massachusetts, U.S.
How humans responded
After experimenting on mice, the researchers signed up human participants. They divided the participants into two groups – offering one group raw food for three consecutive days, and the other one cooked meals prepared by a professional chef. At the end of the third day, they collected stool samples to assess gut microbes.
In humans too, the effect of cooked food on gut microbes remained the same as mice.
“Because cooking is human-specific, ubiquitous and ancient, our results prompt the hypothesis that humans and our microbiomes co-evolved under unique cooking-related pressures,” the researchers wrote.
