Eating fermented foods is healthful because they contain many short chain fatty acids (SCFAs) that can reduce inflammation and lower high blood pressure, high cholesterol, high insulin and high blood sugar levels (Gut Microbiome, May 27, 2023;4 (e11):1–16). A plant-based diet has lots of soluble fiber and resistant starches that are not absorbed in your upper intestinal tract, but when they reach your colon, healthful bacteria there ferment these fibers and starches to form SCFAs. When you eat fermented foods, they already have SCFAs so that you don’t have to wait for the SCFAs to be formed at the end of your intestinal tract (Nutrients, 2022 Apr; 14(7): 1527).

A study from Stanford showed that eating fermented foods such as yogurt, kefir, fermented cheese, kimchi, fermented vegetables and kombucha tea increased the diversity of colon bacteria, which decreased inflammation that is associated with many different diseases (Cell, Jul 6, 2021;S0092-8674(21)00754-6). The more fermented foods they ate, the greater the gain in bacterial diversity. Low microbiome diversity is associated with increased risk for heart attacks, certain cancers, obesity and diabetes (J Human Hypertension, April 25, 2022; 36:952–959).

Your colon contains more than 100 trillion bacteria, and some of these bacteria are beneficial while others are harmful. The harmful bacteria try to puncture your colon cells, which turns on your immune system to cause inflammation. The foods that you eat determine whether you grow healthful or harmful bacteria because colon bacteria eat the same foods that you do. Some foods, such as mammal meat, processed meats, sugar-added foods and fried foods, are known to foster growth of harmful bacteria in your colon. These inflammation-producing foods reduce healthful bacteria and increase the harmful bacteria. Anything that promotes bacterial diversity promotes health, while anything that increases inflammation is associated with greater risk for disease.

Study of Fermented Foods
The researchers at Stanford followed 36 healthy adults for 10 weeks on diets that included either fermented foods or foods that were high in fiber but not fermented. The researchers analyzed blood and stool samples collected during a three-week pre-trial period, the 10 weeks of each diet, and a four-week period after the diet when the participants ate their usual diets. The results showed that after just three weeks, the fermented foods reduced inflammation by decreasing:
• activation of four types of immune cells
• blood levels of 19 inflammatory proteins, including interleukin 6 (IL6), which is linked to rheumatoid arthritis, type II diabetes, and chronic stress.

Other studies also show that fermented foods decease inflammation by changing colon bacteria (Microbiome, Feb 11, 2020;8(1):15). The high-fiber diet did not decrease any of the 19 inflammatory proteins and did not change gut microbial diversity in this short study period, but would be expected to do so over a longer period of time (Science, Aug 11, 2017:357(6351):548-549).

My Recommendations
You already know that I recommend a high-fiber diet that includes plenty of fruits, vegetables, whole grains, beans, nuts and other seeds, and I have frequently suggested that you include fermented foods such as yogurt or kefir. Many other studies have found that fermented foods and soluble fiber are associated with reduced risk for weight gain, diabetes, certain cancers, and heart attacks (Int J Environ Res Public Health, 2023 Feb; 20(3):2481). Increasing your intake of fermented foods can quickly improve your colon bacteria to help reduce inflammation.