Whether you're talking kombucha or kimchi, fermented foods are all the rage. They're taking over grocery store aisles—and being featured in some important clinical trials. Recently, Stanford scientists Dr. Christopher Gardner and Dr. Justin Sonnenburg established that eating a diet high in fermented foods promotes a healthier, more diverse gut microbiome, and lowers inflammation. What does that mean? Why does it matter? In this episode, they chat with Medcan Director of Food and Nutrition Leslie Beck about their groundbreaking new study, the fermentation process, the microbial friends living in our digestive tracts, and how to make sure you're buying the right fermented foods.

Episode 87 webpage

LINKS

Study published in Cell: Gut-microbiota-targeted diets modulate human immune status

Article from Stanford Medicine about the study results

Justin Sonnenburg's bio and his Sonnenburg lab

Christopher Gardner's bio

NYT article by Anahad O'Connor: "How Fermented Foods May Alter Your Microbiome and Improve Your Health"

NYT article by Tara Parker-Pope: "The Dos and Don'ts of Fermented Foods"

NYT article by Anahad O'Connor: "A Changing Gut Microbiome May Predict How Well You Age"

Read Justin & Erica Sonnenburg's book: The Good Gut: Taking Control of Your Weight, Your Mood and Your Long-Term Health

Want to make your own fermented foods? It's easy! Check out this recipe packet by Justin and Erica Sonnenburg from the 2021 Healthy Kitchens, Healthy Lives conference

INSIGHTS

• Food becomes fermented over time when controlled amounts of yeast and bacteria are added to it. "The live bacteria has to sit around long enough to enzymatically convert some of the carbohydrates in the food to alcohol or organic acids," explains Dr. Christopher Gardner. Those alcohols or acids are what give fermented food its sour, tangy taste. They also promote a healthy gut microbiome, which is the community of microbial cells in our digestive tract. "We often think of humans as a single species. We actually are walking ecosystems. We have hundreds to 1000s of species that make up the human body. We harbour so many microbial cells that by cell number, we're actually more microbial than we are human," says Dr. Justin Sonnenburg. [8:45][1:59]
• Eating fermented foods leads to a healthier gut microbiome because the more diverse your microbiome is, the more anti-inflammatory compounds your gut produces. This makes your body less likely to develop inflammatory diseases. "The converse of that is, if you're not eating fermented foods, you may be depressing your microbiota diversity," says Dr. Justin Sonnenburg. High fat diets, artificial sweeteners and the emulsifiers in processed foods contribute to a less diverse gut microbiome, making you more susceptible to inflammation. [10:43]
• During Dr. Christopher Gardner and Dr. Justin Sonnenburg's 10-week study, they fed one group of participants a high-fibre diet, and fed the other group of participants a high-fermented food diet. "What we saw with fermented foods was mind blowing," says Dr. Sonnenburg. "We saw this increase in gut microbiota diversity across the entire cohort... as this was happening, many of their inflammatory markers were decreasing." Participants ate six servings of fermented food a day, up from the zero to half a serving a day they were eating before the study. That might sound like a lot of fermented food, but "different combinations of six servings tended to be about 300 calories. It's not like you were eating fermented food all day long!" says Dr. Gardner. [25:33]
• So how does our gut microbiota protect against inflammation? Dr. Justin Sonnenburg says there are many different pathways in the relationship between gut microbial diversity and inflammation. But a major one involves the byproducts that result from microbes interacting with the food in our gut. "We think the metabolites that the microbes are producing can help to degrade foods that we're eating," says Dr. Justin Sonnenburg. "This is why diet is such an important component of determining how our microbiome connects to our health and our immune status." He and Dr. Gardner hope that their research will lead to a deeper understanding of how we can feed our own communities of microbes in a way that enables them to produce molecules that are leading to a healthier immune system. [40:30]
• Not all fermented foods will increase the diversity of your gut microbiome. So how to make sure you're buying the right fermented foods? "You have to be careful," warns Dr. Justin Sonnenburg. "Many things that claim to be fermented foods are just pickled with something like vinegar." Look for fermented food products in the refrigerated section, with labels that read "contains live microbes," "contains probiotics" or "contains live cultures." Look out for high sugar content as well. Since fermented food is naturally sour, many products have lots of added sugar to mask their taste. Finally, although wine and beer have been fermented, they won't promote a more diverse microbiome! They've gone through a heating process that kills all their bacteria. [44:53]