How likely would you be to give a pill to your pet that could speed up the recovery from episodes of diarrhea, help with allergic skin problems, assist the body to deal with stressful situations, support the immune system and improve the immune response to vaccinations? This sounds like a tale that is unbelievable, but, it is true.

A growing number of studies have shown that probiotics can deliver these beneficial effects in humans and animals. Probiotics are living organisms that confer health benefits in addition to their basic nutritional value.

Probiotics contribute to improvements in intestinal and immune function because they can exert positive effects on the gut microbiome. The gut microbiome is a collection of living microorganisms such as bacteria, fungi, archaea and protozoa. It is estimated that there are 10 times more microorganisms in the gut than there are cells in the entire animal body. Bacteria are a significant part of the microbiome of the gut, and it is no surprise that there is an incredible variety of bacteria types.

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This vast variety of microorganisms results in a complex interaction between the microorganisms in the microbiome. Some of these interactions have been determined but many remain to be identified and understood. In addition, the microorganisms can form a defensive barrier against bad bacteria such as E. coli and salmonella, help to breakdown nutrients in the diet, provide important nutrients for intestinal cells and the body, and regulate the immune system.

The balance of the microbiome is constantly being impacted by factors like stress, altered secretions and motility of the gut, antibiotic use, consumption of certain foods or diet changes, and colonization with bad bacteria. Changes in the microbiome can result in alterations in the intestinal barrier, absorption of nutrients and vitamins, and proper metabolism of bile acids and soluble fiber. In addition, an altered microbiome can result in toxic substances passed in the bile being absorbed back into the body.

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Interestingly, dogs with chronic intestinal problems have been shown to have changes in the microbiome. Some of the bacterial groups that are significantly reduced are ones that produce short-chain fatty acids which play an important role in the health of the large intestine. Other bacterial groups that secrete metabolites with anti-inflammatory properties have also been shown to be reduced in individuals with inflammatory bowel disease.

With the increased understanding of the importance of the gut microbiome and the realization that many disease processes can result from an abnormal microbiome, the use of probiotic products to support the microbiome has dramatically expanded. Numerous probiotic products are available, making selection of the appropriate product difficult.

General guidelines for probiotic selection includes 1) ability of the microorganism to survive passage through the stomach, 2) ability of the microorganism to establish itself on the lining of the intestine, 3) number of strains of microorganisms in the product, 4) number of viable microorganisms in each product dose, and 5) does the product contain a prebiotic.

Ability of the microorganisms to survive passage through the stomach and establish colonies on the intestinal lining is critical. Not all microorganisms can survive the acid in the stomach. For example, microorganisms in yogurt, unless specifically included as a probiotic microorganism, are generally not considered likely to be able to establish in the intestines. Some probiotics products contain one or a handful of microorganism strains while others contain 10-14 strains.

The argument is that products with lots of strains are better. However, this has not been uniformly accepted as an important criterion. Successful therapy with products with a small number of strains has been shown. An additional consideration is the number of microorganisms in each dose of the probiotic. A common recommendation is 3-4 billion microorganisms per dose. Prebiotics are substances that feed the good bacteria and help them to establish. Some prebiotics like FOS (fructooligosaccharides) can also have suppressive effects on bad bacteria.

Another consideration focuses on the question of giving animals probiotics that are intended for humans. Some have argued that these products are not effective in animals, but, research and clinical experience show that these products can be effective in animals. Products intended for animal use have not always performed better.

As the understanding of the gut microbiome increases, the selection of microorganism strains for specific health problems will become possible. This will result in more effective therapeutic use of probiotic products for health maintenance.

Ron Carsten, DVM, PhD, CVA, CCRT was one of the first veterinarians in Colorado to use the integrative approach, has lectured widely to veterinarians, and has been a pioneer in the therapeutic use of food concentrates to manage clinical problems. In addition to his doctor of veterinary medicine, he holds a Ph.D. in cell and molecular biology and is a certified veterinary acupuncturist and certified canine rehabilitation therapist. He practices integrative veterinary medicine in Glenwood Springs.