Martin H. Floch, M.D. is clinical professor of medicine of the Yale University Department of Internal Medicine, editor of the Journal of Clinical Gastroenterology, and the author of Netter's Gastroenterology and Diet and Nutrition Therapy in Gastroenterology. In an interview with Dannon, he discussed the way probiotics operate not only in the small and large intestine, but in the mouth, stomach, and liver.

1. Studies have indicated that certain probiotic cultures have an effect on the cavity-causing bacteria in the mouth.¹ Other probiotics are being studied for their ability to reduce the bacteria that cause bad breath.² What's your view on probiotic activity in the mouth?

There hasn't been a great deal published [compared to findings related to the intestine], but there have been some studies that indicate probiotics could play a role in the maintenance of mouth health. Although the data is scarce, what is available makes sense. If you have the probiotic organisms in your mouth, they would have an effect on the bacterial population of the mouth, including bacteria that may be responsible for cavities and bad breath.

2. What about probiotics in the stomach? Two years ago, researchers Barry Marshall and Robin Warren won the Nobel Prize for discovering that peptic ulcers are caused not by stress, but by a bacterium, Helicobacter pylori.

There's been a lot of activity in this area. Animal and human studies suggest that regular intake of certain probiotic bacteria can affect the presence and activity of H. pylori and its ability to survive⁵. About 50 percent of the population is infected and since this is a worldwide problem it has significant implications. The organisms that have been shown to affect the presence and activity of H. pylori are specific strains of Lactobacillus johnsonni, Lactobacillus GG, and Lactobacillus casei . ^3,4

3. The digestive system includes a number of vital organs that aren't part of the "food pathway" but contribute to it - such as the liver. Do probiotics influence their function?

With the liver, probiotics may be used in patients with fatty liver and cirrhosis. A group at Johns Hopkins was studying it,⁵ and I know that we're studying it here in Yale. When the liver becomes fatty it may also develop inflammation that is called steatohepatitis.

At Yale, Dr. Guadalupe Garcia-Tsao has been studying the translocation of bacteria from the intestine to the liver or peritoneum, which results in infection, and trying to show that certain probiotics would have an effect on the bacteria that would make their way from the bowel to the liver.⁶ More research is needed, but it is a promising field of research.

4. Does probiotic activity in the digestive system appear to translate to benefits elsewhere in the body?

The "extra-intestinal" subject that I find most fascinating, and this affects females, is vaginitis or vaginosis. We know it occurs due to a disturbance in the bacterial balance in the vagina. What is fascinating is that when you feed probiotics orally and they get into the gut, they also get into the vagina. There have been studies of the effect of certain probiotics on vaginal infection. I find that fascinating-it's such a distal site, and yet you can influence it by giving the probiotics orally. For a condition that's so common among women around the world, that's important.⁷

5. Do certain probiotics strains correspond to certain parts of the digestive system in terms of the benefits they provide?

H. pylori in an inhabitant of the stomach, and it appears to be affected by several species of Lactobacillus, whereas a Bifidobacterium will have an impact on the intestinal flora and intestinal function⁸ Thus different species of probiotics have effects in different parts of the gastrointestinal tract. There are many other examples of specific organism effects at specific sites.