Fermented Foods for Healthy Mind & Body
Hey y’all, this week I thought we’d take a look at research examining fermented foods. Although we talk a lot about the gut microbiome here, and foods that can modulate the composition and function of gut bugs, we haven’t really directly addressed the effects of fermented foods.
It's not because we aren’t fans — I eat them every day. The reason why is that there has been a paucity of rigorous studies investigating fermented foods. There is a decent amount of observational data linking fermented dairy products to health outcomes (especially yogurt), and data from the American Gut Project suggests that people who consume fermented foods show a characteristic signature on the gut microbiome. But there hasn’t been a ton of highly specific evidence backing fermented foods, and certainly not enough to justify some of the extraordinary claims made about them.
That is, until recently. Two new-ish randomized trials, one from last year and another from a couple months ago, actually demonstrate some interesting and novel benefits associated with consuming fermented foods. One shows improvements in diversity and inflammation in comparison to a high-fiber diet, the other points to potential psychological benefits for ingesting fermented foods. More info below 👀
This Week's Research Highlights
🦠 A diet high in fermented foods increases microbiome diversity and dampens markers of inflammation.
Researchers at Stanford recruited 36 healthy adults and randomly assigned them to two different 10-week-long interventions. One group was assigned to consume a high-fiber diet, and the second group consumed a high-fermented foods diet. Importantly, participants in the high-fiber group did not increase their consumption of fermented foods, and participants consuming the high-fermented food diet didn’t increase their fiber intake.
Blood and stool samples were collected longitudinally for 3 weeks prior to the diet interventions to get baseline data, then during the 10 weeks that they followed their assigned diets, and finally for a 4 week period during which the participants could eat whatever they wanted.
Adherence to both interventions seems to have been good and resulted in meaningful changes to their baseline diets. For instance, those in the high-fiber-diet arm increased their fiber consumption from an average of 21.5 ± 8.0 g per day up to 45.1 ± 10.7 g per day, and those in the high-fermented-food diet arm increased their average fermented food intake 0.4 ± 0.6 servings per day to 6.3 ± 2.9 servings per day. When the researchers compared data, they found distinct effects from both diets. Individuals in the high-fiber diet arm showed increases in short chain fatty acids, but inflammation and microbial diversity were unaffected. In contrast, the people who consumed fermented foods showed greater overall microbial diversity as well as lower serum levels of 19 inflammatory proteins, and these effects were magnified in those who ate larger servings of the fermented foods. Author Justin Sonnenburg commented,
"This is a stunning finding…It provides one of the first examples of how a simple change in diet can reproducibly remodel the microbiota across a cohort of healthy adults."
Irish researchers recruited 45 adults and randomly assigned them either a control diet or a psychobiotic diet for four weeks. The psychobiotic diet was devised to act upon the gut-brain axis, and was high in fermented foods (2-3 servings per day) as well as grains, legumes, and fruits and vegetables that are high in prebiotic fibers. The control group also received an equal amount of consultation with a registered dietitian, but their input focused mainly on established food guidelines. After four weeks, 32% of participants in the psychobiotic group showed reductions in perceived stress, compared to 17% in the control group. It is worth noting that the psychobiotic group only managed to get about half the recommended servings of fermented foods on average, which may have handicapped the intervention. Benefits appeared to be dose-dependent, meaning that stronger adherence to the diet was linked to greater diminishment of stress.
Media Featuring humanOS
Dan Pardi: Behaviors to Improve Healthspan. Via STEM-Talk.
Dan recently had the opportunity to visit the Florida Institute for Human & Machine Cognition (IHMC) and discuss our work on their podcast. On this show, he talks about his own research in sleep and circadian physiology, the model of behavior modification that he developed during his Ph.D work (the Loop Model), the challenges of defining “health,” the difference between age and aging, and much more!
Random Trivia & Weird News
⚾️ According to a Japanese urban legend, the Hanshin Tigers baseball team has had a curse placed on them — by the ghost of Colonel Sanders.
When Hanshin fans celebrated their team’s victory in the 1985 Japan Championship series, they scooped up a statue of Colonel Sanders that had been situated in front of a KFC and tossed it into a nearby river.
Sports and superstition go hand-in-hand, so this incident was cited as an explanation for the team’s subsequent 18-year losing streak.
The statue was ultimately recovered, as seen here, but with parts missing. It is now thought that the only way to fully break the curse is to recover his lost spectacles and left hand.
Podcasts We Loved This Week
- Justin Sonnenburg & Christopher Gardner: Fermented foods, fiber, and immunity. Via The Proof Podcast.
- Joe Moe: How understanding depression goes beyond the scientific method. Via Science Friday.
Products We Are Enjoying
I just stumbled upon this product recently and it is the tastiest kimchi I have ever had. I say this as someone who has eaten a lot of kimchi and made it myself. It’s made of wholesome ingredients (cabbage, mustard greens, apple, and carrot), not too salty, and it’s even certified vegan so everyone can enjoy it. Easy way to get a dose of probiotics every day. Also quite timely, as kimchi is a traditional New Year food in Korea (albeit for the Lunar New Year).
humanOS Catalog Feature of the Week
Thanks for reading, enjoy the weekend, and we will see y'all next week!