Are fermented foods or high-fiber foods good for your health?

Bread, sauerkraut, yogurt, cheese… A variety of fermented foods constitute our daily diet, becoming the most common and most special food in our lives. Microbes are behind all these foods.
So could fermented foods, which are closely linked to microbes, also affect the gut flora in our bellies?
What does it do to our bodies? Today, we focus on fermented foods. I hope this article can bring some help and inspiration to the relevant industry people and readers.
Fermented food
Fermented foods such as yogurt, pickles, sauerkraut and kombucha have long been staples in many parts of the world. In fact, for thousands of years, different cultures have relied on fermentation to produce bread and cheese, preserve meat and vegetables, and improve the flavor and texture of many foods.
Now, scientists have discovered that fermented foods may have an interesting effect on our gut. Eating these foods may alter the trillions of bacteria, viruses and fungi that live in our gut, collectively known as the gut microbiome. Fermented foods may also lower levels of inflammation throughout the body, and research is increasingly linking them to a range of age-related diseases.
The latest findings come from a study by Stanford University researchers published in the journal Cell. The study explored the possible effects of fermented foods on the gut and immune system, and compared it to a relatively healthy pattern of a high-fiber diet rich in fruits, vegetables, legumes, whole grains, and other fiber-rich foods. Fermented foods vs. high-fiber foods
For the study, the researchers recruited 36 healthy adults and randomly assigned them. One group was asked to increase their intake of fiber-rich plant-based foods, while the other group was asked to eat more fermented foods, including yogurt, sauerkraut, kefir yogurt, kombucha and kimchi.
Fermented foods are made by mixing milk, vegetables, and other ingredients with microorganisms such as yeast and bacteria, so fermented foods are often rich in live microbes, as well as byproducts of the fermentation process, including various vitamins, lactic acid, and citric acid.
The participants followed the prescribed diet for 10 weeks, during which time the researchers tracked and examined changes in inflammatory markers in their blood and in their gut microbiome.
By the end of the study, the first group had doubled their fiber intake, from about 22 grams per day to 45 grams per day, about three times the average intake of the average American. The second group went from eating almost no fermented foods to eating about six servings a day. While six servings sounds like a lot, it’s not as dramatic as you might think: 245g (one cup) of yogurt for breakfast, a 473ml (16 oz) bottle of kombucha for lunch, and 245g (one cup) of pickles for dinner make six servings.
After 10 weeks, there was no significant change in overall immune health measures in either group. But the fermented food group showed significant reductions in all 19 inflammatory compounds. Among the compounds that showed declines was interleukin-6, an inflammatory protein that tends to be elevated in diseases such as type 2 diabetes and rheumatoid arthritis. In contrast, the same inflammatory cytokines were not significantly reduced in the high-fiber group.
For those in the fermented food group, the reduction in inflammatory markers coincided with changes in their gut. Their guts host a wider and diverse array of microbes, similar to other recent studies on people who ingest a variety of fermented foods. New research has found that the more fermented foods people eat, the more variety they have in their gut microbes. Surprisingly, however, only 5 percent of the new microbes detected in their guts appeared to have come directly from the fermented foods they ate.
Justin Sonnenburg, a professor of microbiology and immunology at Stanford University and author of the new study, said: “The vast majority are coming from somewhere else, and we don’t know where. I think either there are more low-abundance microbes than detected, or fermented foods are recruiting other microbes into the gut environment.”
In general, a high level of diversity in the gut microbiome is considered a good thing. Studies have linked it to lower rates of obesity, type 2 diabetes, metabolic disease and other conditions.
People living in industrialized countries tend to have less diversity in their gut microbes than people living in more traditional, non-industrialized societies. Some scientists have speculated that modern lifestyle factors, such as highly processed foods, chronic stress and lack of exercise, may inhibit the growth of potentially beneficial gut microbes.
Others argue that the correlation between a diverse microbiome and good health has been overstated, and that the low levels of microbiome diversity typically seen in people living in developed countries may be appropriate for the modern world. Contrary to expectations
But there is little disagreement among experts on one point: a high-fiber diet has benefits. In numerous studies, people who eat more fruits, vegetables, nuts and other fiber-rich foods tend to have lower mortality rates and lower rates of chronic disease.
Dietary fiber is thought to be beneficial for gut health: microbes in the gut feed on fiber and use it to produce beneficial by-products, such as short-chain fatty acids, which can reduce inflammation. Some studies have also shown that eating a lot of fiber can promote a diverse microbiome.
The Stanford researchers expected that eating a high-fiber diet would have a significant impact on the composition of the microbiome. Contrary to expectations, however, there was little change in microbial diversity in the high-fiber group. But when the scientists took a closer look, they found something surprising: People who started out with higher levels of microbial diversity adopted a high-fiber diet with lower levels of inflammation, while people who started out with lower levels of microbial diversity had a slight increase in inflammation when they ate more fiber.
The researchers say they suspect that people with low microbiome diversity may lack the right microbes to digest all the fiber they consume. One finding that supported this was that participants in the high-fiber group unexpectedly had a large amount of carbohydrates in their stool that had not been degraded by their gut microbes.
One possibility is that their gut needs more time to adjust to a high-fiber diet. But ultimately the finding could explain why some people experience bloating and other uncomfortable gastrointestinal problems when they eat a lot of fiber, said Christopher Gardner, another author of the study.
“Maybe some people’s microbiomes aren’t ready for fiber,” said Gardner, director of nutrition research at Stanford University’s Prevention Research Center.
One question the researchers hope to answer in the future is what happens if people eat more fermented foods and more fiber at the same time. Does this increase the variety of microbes in their gut and improve their ability to digest fiber? Could the two have a synergistic effect on inflammation? Hard evidence
Suzanne Devkota, director of microbiome research at Cedars-Sinai Medical Center in Los Angeles, who was not involved in the new study, said eating fermented foods has long been thought to be good for health, but this new study is the first to provide some “hard evidence” that it can affect the gut and inflammation. “It’s always difficult to say that fermented foods are beneficial, especially from an inflammation perspective, because there’s a real lack of data behind it.” “She said.
Devkota cautioned that these findings should not deter anyone from eating fiber-rich foods, as fiber has many other health benefits beyond its effect on the gut. She also eats a lot of fiber and fermented foods herself, and often advises patients with conditions such as inflammatory bowel disease to do the same.
“It doesn’t change what I’ve been recommending,” she said, “but I might shift more toward encouraging people to eat fermented foods now that I have the data to back it up and it has some anti-inflammatory properties.”
Devkota says more research is needed to better understand the link between fermented foods and overall health. But one reason fermented foods may be beneficial, she believes, is that the microbes they contain are constantly producing various nutrients during fermentation.
“A jar of sauerkraut is a living food, and the microbes inside are actively producing beneficial substances, such as vitamins,” she said. When you eat fermented foods, you’re ingesting all these chemicals that are produced by these microbes, and it’s good for you.”