There is evidence that a person’s diet can determine his or her probiotic content. Some bacteria on foods are encased in biofilms that protect them from destruction by stomach acid.

These organisms have been detected in human stool samples. Their exact role is not known, but they may aid human health and brain function.

Studies have shown that a high-protein diet with a lot of meat favors growth of the Bacteroides species, some of which can be harmful.

A vegetarian diet favors the Prevotella species, which are favorable for health.

A diet high in oligosaccharides, such as found in the prebiotic food fructooligosacchride, encourages the growth of beneficial Bifidobacteria — one of the most abundant and healthful forms of probiotics.

Foods high in these oligosaccharides include raw chicory root, garlic, onions, and raw Jerusalem artichoke. There are also interactions between these probiotic bacteria with the result that some suppress growth of others, and some enhance the growth of other probiotic bacteria.

A special form of bacteria in Swiss cheese enhances the growth of the Bifidobacterium species.