A 2020 systematic review in Recent Patents on Food, Nutrition & Agriculture looked at 35 research studies that investigated how whole grains impact the bacteria in the gut. Most of the studies found that whole grains encourage the growth of bifidobacteria and lactobacilli. Both bifidobacteria and lactobacilli ferment your carbs into short-chain fatty acids that protect your gut’s lining, regulate your hormones, and stabilize your blood sugar. Some strains of bifidobacteria support your immune system and fight infection, and some lactobacilli strains can tame inflammation. Whole grains also reduce the harmful Escherichia coli (E. coli) and clostridia bacteria in your gut.

Sourdough might have become a popular bread during the lockdown days of COVID, but you don’t have to nix it if you want to improve your gut health. According to a 2019 study in Frontiers in Microbiology, sourdough bread reduced the harmful bacteria in the guts of rats. Sourdough also causes the gut bacteria to produce proteins that render some pathogenic bacteria inactive.