Nutrition and GI disease: Assessing ingredients in complete and balanced dietsWhile nutrition is essential to helping resolve and manage gastrointestinal disease, it can be challenging to determine the benefits of specific ingredients January 2, 2020 By Matt Panasevich, PhDIn both companion animal and human nutrition, the concept of gut health is a point of major focus in foods and supplements. As technologies and ingredients evolve, the complexity of diets also increases. Veterinarians are often faced with the challenge of prescribing the right diets that fit both the pet’s needs and its owner’s resources. In the case of gut health, gastrointestinal (GI) disease is a common reason for veterinary consultation in both dogs and cats, creating significant stress on pets and owners alike. Complaints can range in severity from gastritis and constipation to more chronic conditions, including colitis, pancreatitis, and inflammatory bowel disease (IBD). Currently, IBD is considered a common cause of chronic diarrhea and vomiting in dogs and cats.1,2 The disease’s exact cause is not fully understood; however, imbalances in the gut microbiota and specific pathogens are considered major causes and/or consequences of IBD. Management of the condition is focused primarily on controlling the symptoms, eliminating the potential cause, and focusing on recovery of the GI tract. A number of pharmacological and antimicrobial interventions have been clinically proven to help resolve and control future relapses of GI conditions. Although antibiotics can be effective, the inappropriate use of them may cause risk of resistance as well as dysbiosis, a severe imbalance of diversity in the gut microbiota that can present a major problem. Taking a closer look Nutrition is essential to helping resolve and manage GI issues. However, both pet owners and clinicians are inundated with nutritional information on the benefits of specific ingredients. Prebiotics (i.e. ingredients that stimulate growth and/or activity of beneficial gut bacteria); probiotics (i.e. live microorganisms that confer benefits to the host when consumed); or even a combination of pre- and probiotics (synbiotics) are often in the purview of both the consumer and clinician. There is a tendency to prescribe or recommend products simply because they contain one or two of these ingredients; however, these are not necessarily representative of the product itself. Individually, these ingredients are continually being validated scientifically; however, veterinary professionals should consider how they are validated versus how they are applied in complete and balanced diets, and, ultimately, prescribed and recommended. Both commercial and prescription diets offer a collection of ingredients designed to work synergistically to provide various nutrients that are beneficial to gut health. With the robust knowledge nutritionists have on many individual ingredients, the approach should begin to extend beyond validation of a single ingredient to understanding how groups of ingredients work in synergy to optimize gut health and recovery. There is growing evidence the gut microbiome—which is a collection of microorganisms that include bacteria, viruses, protozoa, and fungi residing throughout the GI tract—plays a pivotal role in gastrointestinal disease. We know acute and chronic diarrhea patients have a less diverse microbiome than healthy animals, as well as lower concentrations of select beneficial bacteria important for producing short-chain fatty acid metabolites, which are essential for gut recovery and healing.3 Further, nutrition can play a role in combating this dysbiosis. Specifically, ingredients that provide sources of fiber and/or prebiotics directly impact the gut microbiome by promoting beneficial bacteria and short-chain fatty acid production, which are lower in cases involving acute and chronic IBDs. As such, dietary fibers and prebiotics are continually being evaluated for gut health, as well as feasibility in diets. These studies often involve highly controlled diets with equal amounts of macronutrients. Their goal is to investigate the inclusion of an ingredient ranging from zero percent to a higher concentration in the diet to evaluate gut health outcomes, as well as assess their impact on stool consistency, palatability, and nutrient digestibility in healthy animals. There is growing evidence the gut microbiome—which is a collection of microorganisms that include bacteria, viruses, protozoa, and fungi residing throughout the GI tract—plays a pivotal role in gastrointestinal disease. For example, common prebiotic ingredients such as inulin/fructooligosaccharides (FOS) and yeast-derived prebiotics (mannanoligosaccharides [MOS]) have been studied extensively to assess their benefits to gut immune health, fecal microbiota concentrations, fecal metabolites, stool consistency, and digestibility in healthy animals.4,5 To be noted, these studies provide invaluable data to nutritionists that formulate diets to devise an appropriate dose of that particular ingredient, without sacrificing nutrition of the whole diet. Both commercial and prescription diets, however, are more complex in composition, providing a variety of ingredients delivering different nutrient profiles that confer an array of benefits to gut health. Rather than one dietary fiber source, diets often contain a mixture of dietary fibers where individually they have different concentrations of insoluble and soluble fiber and may contain differing concentrations of protein, fat, and minerals, which should be taken into consideration. Along with individual assessment of novel ingredients, investigating groups of ingredients to evaluate their synergistic effects on gut health to deliver clinical outcomes should be studied with the same rigor. Assessing fiber blends This approach was taken in recent studies where a fiber blend consisting of apple pomace, flaxseed, cranberries, pumpkin, and inulin was investigated for clinical efficacy in both acute and chronic diarrhea animals.6-8 The goal was to assess the fiber blend as the dietary dose of insoluble and soluble fiber strictly on clinical efficacy, including improving stool consistency and ability to promote quicker time to resolution of diarrhea in shelter kittens and puppies with acute diarrhea, as well as stool characteristics in adult cats with chronic diarrhea. In both the shelter kitten and puppy studies, animals were randomly assigned test and control diets for seven days where stool scores were assessed twice daily. Diets containing the mixed-fiber blend lowered average stool scores (3.78 versus 3.38 average stool scores) and resulted in quicker resolution of diarrhea (4.43 versus 3.78 days resolution) compared to the control diet, which was lower in total and soluble fiber. In the shelter kitten study, the mixed-fiber blend did not change average stool scores; however, it promoted quicker resolution of diarrhea (5.4 versus 4.1 days to resolution) compared to a diet lower in total and soluble fiber. A 28-day randomized crossover design study also was conducted in cats with chronic diarrhea. Here, stools were scored on a scale of one to five, where “1” is firm and “5” is diarrhea. Stools scored in the range of “1” to “3” were categorized as “pick up” and stools scored “4” to “5” were categorized as “wipe up.” The mixed-fiber diet lowered average stool scores (3.15 versus 2.98 average stool scores) and resulted in categorically better stool scores (200 versus 251 number of “pick up” stools and 172 versus 112 number of “wipe up” stools) compared to the control diet. As further validation of the fiber package, stool quality, palatability, and digestibility were evaluated in clinically healthy animals. The results showed ideal stool consistency scores, high palatability, and no detriments to nutrient digestibility. It is important to note that individual ingredients within the fiber blend studied have been investigated for their impact on gut health in healthy animals.9,10 Collectively, in a complete and balanced diet, the clinical impact and performance of these ingredients on the GI tract was not well understood. The approach of assessing the synergistic impact of how ingredients deliver nutrition, and ultimately a positive clinical outcome, is appropriate to what veterinarians eventually recommend to their patients. In addition, evaluating gut microbiome changes, fecal metabolite concentrations, and gut immune outcomes in response to a collection of ingredients as the test/stimulus would certainly advance our scientific understanding of nutrition’s role in combating GI disease. To be clear, this does not negate the need to continually validate individual ingredients for their nutritional efficacy and safety. However, tailoring nutritional studies on gut health where the active ingredients are studied as a group or bundle offers a real-world look at what veterinarians and pet owners are providing to their pets. With new developments in nutrition relevant to gut health (e.g. pre- and probiotics), understanding the clinical and scientific relevance of these ingredients individually, as well as synergistically, needs to be addressed further. Matt Panasevich, PhD, is a companion animal nutritionist and a senior nutrition scientist at Blue Buffalo Co., in research and development. His background and experience have focused on the impact of diet and ingredients on the gut microbiome and the implications they have on health and disease. Dr. Panasevich helps validate the use of new ingredients, formulations, and nutritional performance in complete and balanced pet foods. He has shared his expertise through scientific contributions in more than 12 peer-reviewed publications, three patents, and numerous conference abstracts and seminars in both companion animal and human nutrition. References Guilford WG. Nutritional management of gastrointestinal diseases. 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