Dr. Mona S. Miller lives in Lafayette with her 4 year old son, yellow Labrador Retriever and grey cat. She has worked at Four Seasons Animal Hospital in Lafayette since moving here in 2001. She attended Cal as an undergrad, and received her DVM from U.C. Davis. She can be reached at Four Seasons, 938-7700, or by email to MonaSDVM@aol.com.

The use of probiotics in veterinary medicine is becoming very popular, and certainly has a role in such disease problems as chronic diarrhea and inflammatory bowel disease. Additionally, given that the gastrointestinal tract is the largest immune organ in the body, there may be some benefit in using probiotics as a general immune stimulant. In human medicine, probiotics can be very useful in treatment plans for ulcerative colitis, inflammatory bowel disease and infectious diarrhea. However, there is still a lot that we don't know about the use of this type of supplement.
What is a probiotic? A probiotic is a protected culture of live "good" bacteria that can colonize the lower intestine. Thus, it must be protected from stomach acid so that it can move into and attach to the inner wall of the lower intestine. There the bacteria make by-products that are nourishing to the intestine and the local immune system cells found in the gut. This bacterial fermentation activity contributes 10% of daily energy requirements for humans, but only 2-7% of maintenance energy for dogs, and very little for cats. From this it can be inferred that probiotics are more important for herbivores and omnivores than carnivores. The type of "good" bacteria varies from species to species, and the ideal probiotic should originate in the species being treated. Crossover may not be effective - that is, a human probiotic may not be beneficial for a dog or a cat.
Probiotics may have some negative effects as well, and sometimes with severe consequences. It has been demonstrated in human studies that too much probiotic in an immune-compromised individual may cause bacterial invasion of the bloodstream (septicemia). According to a recent veterinary article, there have been no reports of the same occurring in animals. However, the author of this review advised caution if probiotic supplementation was to be considered in animals who are severely immune-compromised, critically ill, or have severe intestinal disease.
There is huge variability in quality control of probiotics. These are not FDA-approved products for humans or animals. Several studies have documented inconsistencies between what appears on the label and what is actually in the product. My advice is to consult with your veterinarian and pick something that is most likely to contain what it says it does (it will probably be a veterinary product from a major company involved in nutritional research like Iams or Nestle-Purina).