Many people know that both good and bad bacteria inhabit the gut. But fewer folks may realize that certain foods can increase the number of the right microbial colony-forming units (CFUs) in their belly.

According to experts, the best foods for a healthy gut are those rich in fiber or other nutrients and fermented fare. This is because they contain either beneficial bacteria known as probiotics or prebiotics, the stuff that fuels these good microbes.

Found in certain fruits, veggies and whole grains, fiber is, perhaps, the best-known prebiotic. Two types of fiber, soluble and insoluble, provide gut bacteria with the energy, vitamins and special fatty acids needed to boost immune function, decrease inflammation and protect against obesity.

Fermented foods include pickled cabbage, such as sauerkraut and kimchi, and other brine-soaked veggies (think cucumbers) as well as soybean products, such as miso and tempeh. (Beware their salt content, however.)

In addition, cultured dairy products, such as plain yogurts and kefir (both available made from nondairy sources), and dandelion greens, seaweed, flaxseed, garlic and gum arabic offer a wide range of bacteria strains to boost the number of CFUs populating the gut.