Although dietary fiber is essential for the function of the intestines, there are more effective dietary approaches for the microbiota.

Yogurt smoothie with seeds.

A diet abundant in fermented foods increases the diversity of intestinal microorganisms beneficial to health and reduces molecular signs of inflammation, according to a study by researchers at the Stanford School of Medicine published in the journal Cell.

In a clinical trial, 36 healthy adults were randomly assigned to dietary patterns for ten weeks, one of which was rich in fermented foods and the other in fiber. Both approaches produced different effects on the gut microbiota and the immune system.

Consume products such as yogurt, kefir, fermented fresh cheese, kimchi and other fermented vegetables like sauerkraut, kombucha tea, or pickles led to an increase in the diversity of the microbiota – the microbial community that inhabits our gastrointestinal tract – with greater effects at higher consumption.

“It’s an amazing finding,” says Dr. Justin Sonnenburg, associate professor of microbiology and immunology, and one of the authors. “Provides one of the earliest examples of how a simple change in diet can reliably reshape the microbiota of an entire cohort of adults without health problems ”.

In addition, it was found that four types of immune cells showed less activation in the group that ate fermented foods. Levels of 19 inflammation-related proteins in the blood also decreased. One of them, interleukin-6, is linked to problems such as rheumatoid arthritis, type 2 diabetes, and chronic stress.

In contrast, none of these 19 proteins were reduced in participants who had been assigned the high-fiber diet, which was provided by legumes, seeds, whole grain, nuts, vegetables and fruits. Despite the healthy profile of this pattern, the diversity of the microbiota remained stable.

“We expected that high fiber intake would produce an overall beneficial effect and increase the variety of microorganisms,” explains Dr. Erica Sonnenburg, a researcher in the Department of Life Sciences, Microbiology and Immunology. “The data suggest that the consumption of fiber, by itself and in a short period of time, is not enough to produce this diversity“.

Based on the available scientific evidence, the researchers wanted to see which approach to healthy nutrition would be the most effective in modifying the microbiota. The high-fiber diet has been shown to reduce premature mortality For all reasons, while consuming fermented foods can help maintain a healthy weight while reducing the risk of cardiovascular disease, metabolic disease and cancer.

During the ten weeks that the trial lasted, the researchers analyzed blood and stool samples, which they compared with the period before and four weeks after the completion of the diet. In those moments,s participants were free to eat whatever they wanted.

The results indicated that a higher fiber intake led to a higher concentration of carbohydrates in the stool, which points to incomplete degradation by intestinal microorganisms.

This is related to another piece of information, which people who eat the ‘western diet’ style have fewer bacteria capable of metabolizing the dietary fiber found in fruits and vegetables. The researchers suggest that, if the trial continued for a longer period, the microbiota would have adapted to optimize this consumption.

“There are many ways in which we can intervene on the microbiota through food and supplements, and we look forward to further investigating how different diets, probiotics and prebiotics, impact the microbiome and health in different groups of people, ”concludes Sonnenburg.