Immunonutrition therapy is a discipline wherein the goal is to enhance immune system activity by including specific nutrients in the diet.  In humans it has been shown to be effective in critically ill patients, including those with serious burns. In spayed and neutered dogs immunonutrition therapy can be an effective adjunct to hormone balancing. Although many spayed and neutered dogs have an insatiable appetite, others (this would include Billy and our previous spayed dog Sally) are anorexic with chronic diarrhea.

To bolster Billy’s immune system and deal with his GI tract issues, a holistic vet who treated Billy recommended supplementation with l-glutamine. Before administering l-glutamine to Billy, we did some research. L-glutamine is an amino acid that is utilized at a high rate by the cells compromising the immune system and the gut. The maintenance of plasma glutamine concentrations in patients at risk of immunosuppression (e.g. spayed and neutered dogs) has the added benefit of maintaining immune function. Animal studies have shown that inclusion of glutamine in the diet increases survival to a bacterial challenge.¹⁶⁸

We found l-glutamine is considered to be a prime immunonutrient in immunonutrition therapy and experimental and clinical studies demonstrated that l-glutamine, administered in animals or human patients, can:

• abate intestinal injury
• accelerate repair of intestinal mucosa
• improve nitrogen balance
• abate immunosuppression
• maintain immune homeostasis
• ameliorate wound healing
• shorten hospital stay

Although the use of l-glutamine for supportive care of severely burned patients is now well established, the science of its use is still in its infancy.^168,169,170

The holistic vet instructed us to give Billy 1 teaspoon L-glutamine powder mixed in his food twice a day. The vet warned us his poop would be all colors of the rainbow for about a week, and then would improve. It happened just that way – yellow, orange and green poop, sometimes with heavy mucous. After one week, Billy’s diarrhea was gone and he was doing much better! The vet did not advise us of any downside to the l-glutamine, and certainly Billy’s skin infections and digestion only improved with its use. With respect to dosage, Billy weighed 60-65 pounds. Certainly a holistic vet should be able to help you with dosage if your dog is much smaller or larger than Billy. A review of the literature does not reveal adverse effects with normal doses of l-glutamine; the only contraindication we have found to glutamine supplementation in moderation is that it may not be safe for those suffering from epilepsy or prone to seizures.

It seems appropriate to include a discussion of probiotics here, as these are often recommended by vets (especially holistic vets) in situations where dogs have impaired function in their GI tract. Certainly dogs who suffer from a compromised immune system are prescribed antibiotics more often as they can develop frequent infections. Generally, probiotics are recommended to rebuild the gut microbiome after a round of antibiotics. The holistic vet did recommend we try probiotics for Billy, and when she determined probiotics did not help Billy (we agreed), she then directed us to try glutamine.

It is important to note that recently two new studies show that whereas some human patients appear to benefit of probiotics, others may have little response or potentially adverse reactions to the supplements. One study concluded probiotics perturb rather than aid in microbiota recovery back to baseline after antibiotic treatment. Another study concluded evidence of probiotic gut mucosal colonization efficacy remains sparse and controversial; in part because current methods of evaluating microbiome content are flawed. Further, probiotic efficacy is highly variable, meriting development of new personalized probiotic approaches. Perhaps most disturbing is now that we know probiotics can be harmful, we find few earlier studies on probiotics assess or report potential harms.

In fact, a systematic review of available studies concluded: “Harms reporting in published reports of Randomized Controlled Trials assessing probiotics, prebiotics, and synbiotics often is lacking or inadequate. We cannot broadly conclude that these interventions are safe without reporting safety data”.

It is therefore, not surprising that experts such as Dr. Pieter Cohen of Harvard Medical School advise consumers to be “cautious and skeptical” when contemplating the use of probiotics.