❓ Is it true that "fermented foods are good for you"? Let's look at it from a scientific perspective.
Many people have likely heard that "fermented foods seem to be healthy."
These foods, such as yogurt, kimchi, miso, and nukazuke (rice bran pickles), have long been familiar parts of the Japanese diet.
Recently, along with terms like "gut health activities" (chōkatsu) and "gut flora," attention is once again focusing on their functions.
But have you ever wondered:
"Specifically, how do they have a positive impact on the body?"
"Do they really reach our gut and bring about change?"
An intriguing study offering hints to answer these questions was published in 2021 by a research team at the prestigious Stanford University School of Medicine in the United States.
🔍 Study Overview: Fermented Foods vs. High-Fiber Diet – What Changed in the Gut and Body After 10 Weeks?
In this study, healthy adults were divided into two groups. For 10 weeks, each group followed a specific diet, and researchers compared the changes observed in their gut bacteria and various indicators in their blood.
- Fermented Foods Group: Incorporated a variety of fermented foods into their daily diet.
- High-Fiber Group: Incorporated plenty of fiber-rich foods (like vegetables, legumes, nuts, seeds, whole grains) into their daily diet.
🍽️ Examples of What the Fermented Foods Group Consumed:
Yogurt, kefir (fermented milk), fermented cottage cheese, kimchi, fermented vegetables like sauerkraut, vegetable brine drinks, kombucha, etc.
Participants chose from these fermented foods and gradually increased their intake over the 10 weeks (aiming for about 6 servings per day).
📊 Main Findings of the Study (Results):
✅ [Fermented Foods Group] Increased Gut Bacteria "Diversity"!
The group consuming plenty of fermented foods showed a significant increase in the variety (diversity) of bacteria living in their gut. High gut bacterial diversity is generally considered indicative of a more stable and balanced gut environment.
✅ [Fermented Foods Group] Decrease in Inflammation-Related Markers
Blood tests revealed a decrease in multiple (19 types mentioned in the paper) potential indicators of the body's inflammatory state (proteins called inflammatory markers, e.g., interleukin-6). This suggests that consuming fermented foods might help temper excessive inflammatory responses in the body.
✅ [High-Fiber Group] No Significant Changes in These Specific Markers
On the other hand, the group consuming plenty of fiber, also considered beneficial for the gut, did not show the same significant changes observed in the fermented foods group regarding the gut bacterial diversity and specific inflammatory markers measured in this study. (Note: Fiber has other important health benefits.)
🔬 Why is "Gut Bacterial Diversity" Important?
Our intestines are home to a vast community of diverse bacteria, estimated to number in the hundreds of trillions. This bacterial community, often called the "gut flora" or "gut microbiota," plays various essential roles in maintaining our health, such as helping us break down food and absorb nutrients, synthesizing certain vitamins, and supporting the function of our immune system.
Generally, the richer the variety of gut bacteria (higher diversity), the more resilient the gut environment is thought to be against various external changes (dietary shifts, stress, illness), leading to greater overall balance. This balanced gut environment forms one of the foundations supporting whole-body health.
🍴 What You Can Do in Your Daily Diet
This research suggests that our daily diet can influence our gut environment and, consequently, our overall body balance.
🔹 Examples of Easy-to-Incorporate Fermented Foods:
- Breakfast: Plain yogurt, Natto (fermented soybeans)
- Side dish: Kimchi, Nukazuke (rice bran pickles), Sauerkraut
- Soup: Miso (avoid overheating)
- Drinks: Amazake (non-heated, rice koji type), Kefir, Kombucha, etc.
It's recommended to start with what suits your body and preferences and continue without overdoing it.
📚 Source & References
- Original Paper: Wastyk HC, Fragiadakis GK, Perelman D, et al. Gut-microbiota-targeted diets modulate human immune status. Cell. 2021;184(16):4137-4153.e14. doi:10.1016/j.cell.2021.06.019
https://doi.org/10.1016/j.cell.2021.06.019 - Stanford University News Article (for general audience, English): "Fermented-food diet increases microbiome diversity, decreases inflammatory proteins" - Stanford Medicine News Center
https://med.stanford.edu/news/all-news/2021/07/fermented-food-diet-increases-microbiome-diversity-lowers-inflammation
✨ Conclusion
Beyond the intuitive understanding that "fermented foods are good for you," scientific research is beginning to shed light on their potential.
The Stanford University study presented here is an interesting example suggesting that regularly consuming a variety of fermented foods may enrich the diversity of gut bacteria and potentially moderate indicators related to inflammation in the body.
However, the effects of food and how they impact the body can vary depending on individual constitution and the state of one's gut environment.
Rather than overthinking it, why not try mindfully incorporating some fermented foods into your daily meals, paying attention to how your body feels?
※ Disclaimer
The information provided on this page is for general health information purposes only and is not intended to diagnose, treat, cure, or prevent any disease. It is not a substitute for professional medical advice. If you have concerns about your health condition, please consult a physician or qualified healthcare professional. Any actions taken based on the information on this page are at your own discretion and responsibility.