Peas are a good source of soluble fiber, Fitzgerald said. Soluble fibers “help to add bulk and move food through the gut.” Other benefits of soluble fiber include lowering cholesterol, stabilizing blood sugars, and feeding healthy gut bacteria, she noted. Fiber stimulates the growth of beneficial gut bacteria. There is evidence that people on fiber-rich diets have more indolepropionic acid, an anti-inflammatory chemical made by gut bacteria, which may help prevent diabetes, according to a recent Finnish study.
In general, one of the best sources of fiber, other than fruits and vegetables, are whole grains, Fitzgerald noted. Whole grains contain indigestible fiber, which is fermented by the gut microbiota, producing fatty acids that help maintain proper gut health. Whole grains help reduce the amount of Enterobacteriaceae, bacteria found in the intestinal flora that can trigger inflammation, according to a 2017 study published in the American Journal of Clinical Nutrition.
A preliminary study by the Institute for Food Safety and Health from the Illinois Institute of Technology has shown that red raspberries may help improve the ratio of Firmicutes and Bacteroidetes, bacteria generally dominant in the gut. The ratio usually decreases with age. Raspberries are also very high in fiber, which is good for gut bacteria and food digestion.
Green tea is a good source of polyphenols, which help the production of healthy microbes in the colon. Consumption of green tea has been shown to increase the Firmicutes-to-Bacteroidetes ratio and levels of short-chained fatty acids, which are key to good gut health. Green tea also helps reduce Fusobacterium, a bacteria that may cause numerous infections and colorectal cancer.
Pickled vegetables that have been fermented naturally — not using vinegar — are a rich source of probiotics. Some of the known benefits of kimchi, aside from helping with constipation and colorectal health promotion, may include anti-cancer and obesity, cholesterol reduction, and boosting the immune system.