The lining of the small intestine is a major barrier tissue whose function is directly supported by the integrity of its structure. The gastrointestinal mucosa forms a barrier between the body and the lumen of the intestines. The role of this barrier is to selectively allow the passage of nutrients and other small molecules across the epithelium of the intestine, while blocking larger, harmful molecules. Disruptions to this barrier can lead to possible autoimmune disease, food allergies, mood disorders, and other conditions. Disruption to the intestinal epithelial barrier, namely increased permeability, leads to overall gut dysfunction and subsequent GI-related diseases, including irritable bowel syndrome, celiac disease, and leaky gut syndrome. Factors that affect gut permeability include infection, inflammation, immune dysfunction, environmental toxins, medications, and the composition of the gut microbiota. Lipid and zinc deficiencies have also been shown to disrupt tight junctions, alter membrane permeability, and cause intestinal ulcers. The probiotic species Bifidobacterium longum has been shown to prevent damage to intestinal cells as well as increase the production of tight junction cell proteins, improving intestinal integrity. It has also been shown to successfully treat increased permeability in patients with Crohn’s disease and ulcerative colitis. Antioxidants have also been shown to help prevent oxidative damage to the intestine. These include vitamin C, vitamin E, beta-carotene, grape seed extract, milk thistle, and quercetin. Foods that can damage the gut include gluten, dairy, and sugar. Even in non-celiacs, gluten consumption may damage zonulin production, which is a protein that is crucial in tight junctions, increasing permeability to unwanted molecules (we call this non-celiac gluten sensitivity). Dairy can be inflammatory for a lot of people, so it is best to avoid it when trying to prevent damage to the gut. Too much sugar in the diet feeds the bad bacteria in the gut, causing an overgrowth of bacteria and degradation of gut permeability. Nutrients that can provide some treatment to the intestine once it is compromised include L-glutamine, which is the primary amino acid source for intestinal cells and regulates intercellular junction integrity, and N-acetylglucosamine (NAG), which is a substrate for the glycosaminoglycans that are normally broken down in a leaky gut. A leaky gut diet should consist of bone broth, steamed vegetables, fermented foods, and healthy fats. Bone broth contains NAG, as well as collagen and glutamine, which are both elements that make up the gut, while steamed vegetables and healthy fats help provide essential nutrients, like L-glutamine, that keep the gut working properly. Fermented foods contain necessary probiotics, which keeps the microbiota in the gut healthy. Consuming a balanced diet and maintaining a regular exercise routine can aid in healthy and efficient regeneration of musculoskeletal cells as well as maintain current bone density, joint flexibility, and muscle strength. Resistance training of large muscle groups (biceps, triceps, chest, upper back, thighs, and abdominal wall) to fatigue with sets of 8–12 repetitions should be done two to three times a week. Also, consuming 25–30g of protein containing at least 2.5 g of leucine (a branched chain amino acid) can augment muscle building from resistance training and can slow age-related sarcopenia. It is also important for an individual to consume high quality protein on a daily basis of approximately 1g per kilogram of lean body mass.
Integrative and Functional Medical Nutrition Therapy by: Diane Noland, Jeanne A. Drisko, Leigh Wagner
