Kombucha, Kimchi, and Kefir: The Fermented World

Authored By: Alivia Shen

Art By: Amber Briscoe

The other day, I visited my favorite taco restaurant and saw a new special: pork tacos topped with kimchi! There is something so magical about a stinky jar of fermented kimchi or a nice can of crisp kombucha. College students tend to stick to their familiar favorites, like pizza or fries, but we often forget that we also have to be mindful of what we are putting into our bodies. Fermented foods are beneficial due to their enhanced levels of vitamins and antioxidants, ability to lower heart disease, and digestibility. Additionally, fermented foods improve mood and boost immunity, which are super important for maintaining a feeling of good every day and preserving longevity [1]. 

Before understanding how fermented foods impact our gut, we must first be able to break down the science of fermented foods. Take kimchi, a simple Korean pickled dish that hosts around 250 billion living cells in just one serving (250 grams) [3]. Kimchi is primarily made of napa cabbage and other vegetables smothered in Korean chili paste and sealed tightly to ferment. Temperature and salt are two essential things to keep controlled when fermenting kimchi. The temperature must be kept at a certain point to prevent the bacteria's growth. The salt prohibits the growth of unwanted bacteria and promotes the growth of bacteria vital for preservation. In this environment, kimchi hosts a wonderful array of healthy bacteria during fermentation.

At Stanford Medicine, researchers observed how adding fermented foods impacted healthy adults’ gut microbiome [5]. In the clinical trial, 36 healthy adults were randomly assigned to a 10-week diet that included either fermented or high-fiber foods. At the end of the study, the fermented group saw an increase in microbiome diversity compared to the fiber group. Additionally, blood samples of those in the fermented group showed lower concentrations of 19 inflammatory proteins. One of the inflammatory proteins, interleukin 6, is linked to conditions such as arthritis, Type 2 diabetes, and chronic stress. This study shows that a change in one’s diet can quickly alter the makeup of their microbiome. Christopher Gardner, a senior author and principal investigator of the abstract, stated that the authors wanted “to conduct a proof-of-concept study that could test whether microbiota-targeted food could be an avenue for combatting the overwhelming rise in chronic inflammatory diseases.” 

So why is preserving gut health so important? Many do not know the direct link between the microbiome and mental health. The gut microbiome can impact our vagus nerve and neuro-immune signaling, directly influencing our mental health [4]. The vagus nerve is responsible for overreactions that can trigger feelings of anxiety and dizziness. Additionally, studies have shown that our gut also impacts the production of neurotransmitters such as serotonin and dopamine, both of which heavily influence our mood. In one study, anxiety was targeted to see the correlation with microbiomes. Patients with anxiety had much lower levels of Faecalibacterium spp. (positive gut bacteria) than patients with no anxiety. This indicates a correlation between gut bacterial presence and anxiety levels. Another study showed that mice with higher levels of anxiety had significantly lower levels of Firmicutes. It is evident from these studies that there is a relationship between gut health and mental health [2]. 

While fermented foods are becoming increasingly popular, access to these probiotic powerhouses should be more widespread. Unfortunately, many people are swayed away from consuming fermented foods due to their pungent smell and the common intolerance to histamines present in many of them. Introducing more fermented options in college dining halls may have the potential to improve students' mental health significantly.  

Works Cited

1. "Foods with Highest Probiotic Content." Revolution Fermentation, revolutionfermentation.com/en/blogs/other/foods-with-highest-probiotic-content/. 

2. Ghosh, Pritha, et al. "Gut Microbiota and Health: A Review." PMC, vol. 10384867, 2023, www.ncbi.nlm.nih.gov/pmc/articles/PMC10384867/.

3. Kim, Ji Sun, et al. "Understanding Kimchi: A Culinary and Scientific Exploration." Cook's Science, Pote.com, www.cooksscience.com/articles/experiment/understanding-kimchi/index.html. 

4. Oka, Hiroshi, et al. "The Impact of Fermented Foods on the Human Microbiome." Journal of Physiological Anthropology, vol. 33, no. 2, 2014, jphysiolanthropol.biomedcentral.com/articles/10.1186/1880-6805-33-2.

5. Sato, Takashi, et al. "Fermented Food Diet Increases Microbiome Diversity and Lowers Inflammation." Stanford Medicine, 8 July 2021, med.stanford.edu/news/all-news/2021/07/fermented-food-diet-increases-microbiome-diversity-lowers-inflammation.