We, of Ashkenazi Jewish lineage, are acutely aware of the diseases prevalent in our heritage. One of those diseases, Crohn’s disease occurs when bacteria residing in the intestinal lumen invade an unusually permeable intestinal wall resulting in severe inflammation, causing abdominal pain and diarrhea. Crohn’s disease frequency is increasing at an alarming rate. This increase correlates with changing dietary habits, an increased intake of animal fats and processed foods and a decreased intake of fiber. It becomes important that we understand the disease so to minimize its effects.
In the following paragraphs we will discuss the genetic and dietary factors associated with Crohn’s disease.
To properly evaluate causation, we must understand the normal gastrointestinal (GI) tract anatomy and function and the abnormal changes occurring with Crohn’s disease. The GI tract is composed of the oropharynx (mouth and upper throat), esophagus, stomach, small intestine (composed of duodenum, jejunum and ileum) and colon. Crohn’s disease, although most prevalent in the ileum, may occur anywhere in the GI tract. The function of the GI tract is to ingest, digest and absorb food. Digestion occurs primarily in the mouth, stomach and duodenum, proteins being reduced to amino acids, fats to glycerol and fatty acids and oligosaccharides and starches to monosaccharides. Man cannot digest carbohydrates more complex than starch, such as fiber or cellulose. Absorption of digested food occurs throughout the GI tract. Bacteria living in the oropharynx may be found passing through the stomach and duodenum but because of their acid and enzyme content, bacteria do not colonize in these organs. Bacteria live symbiotically in increasing numbers in the jejunum, ileum and colon, the host offering nutriments to the bacteria primarily in the form of complex carbohydrates, and the bacteria digesting the nutriments, making byproducts available to the host, particularly important are short-chain fatty acids which benefit the intestinal mucosa. The relationship between host and symbiotic bacteria depends on a functional intestinal wall and non-pathogenic intestinal flora. The lining cells of the intestine are tightly adherent, creating a physical barrier to bacteria. Specialized cells produce protective mucus containing bactericidal chemicals and transmit bacterial products to a properly modulated immune system which will put antibodies in the protective mucus layer and produce properly modulated immunologically primed cells in the intestinal wall.
In Crohn’s disease, the system breaks down when the intestinal wall barrier allows bacteria to become invasive and the immune system to become aggressive. Several defective genes that control these functions have been associated with Crohn’s disease including NOD2, a gene that plays a role in producing the previously described secreted bactericidal chemical, ATG16L1, a gene involved in properly processing bacteria, and IL-23R, a gene responsible for modulating the immune response. Experimental studies have been designed to clarify the role played by food in Crohn’s disease.
An extensive literature exists on the effect of diet on the symbiotic flora.
* Animal fats have been shown to have detrimental effects, milk fat altering bile composition allowing bacterial growth causing mucosal inflammation.
Other animal fats decrease bacteria that produce short-chain fatty acids and anti-inflammatory agents.
Plant fats rich in omega 3 fatty acids have been shown to be beneficial by reducing inflammation in the intestinal epithelium.
* Because our modern diet has an excess of simple carbohydrates, an excess proceeds to the distal GI tract, decreasing the population of short-chain fatty acid-producing bacteria. As our modern diet has decreased fiber intake, symbiotic bacteria have sought other sources of nourishment such as host epithelium and its mucus covering, causing injury and susceptibility to infection. Decreasing their population allowing replacement by parasitic flora.
* A Gluten-fortified diet has been shown to be associated with inflammation of the intestinal wall. Many food additives including maltodextrin, carboxymethyl cellulose, polysorbate, carrageenan, some artificial sweeteners, have been shown to adversely affect the intestinal flora, causing inflammation.
A number of diets have been used for Crohn’s disease patients to induce or retain remission.
Exclusive Enteric Diet (EEN): use of a liquid diet containing controlled amounts of protein simple carbohydrates and lipids. Crohn’s Disease Treat Diet (CD-TREAT): An oral diet designed to mimic the contents of the liquid EEN diet.
Crohn’s Disease Exclusion Diet (CD-ED): Avoids gluten, dairy products baked goods, animal fat, processed meat, products containing emulsifiers and carrageenan.
Specific Carbohydrate Diet (SCD) (14): Based on the concept that polysaccharides are poorly absorbed, the SCD diet was initially developed for Celiac’s Disease removing wheat, barley corn, rice, added sugar except honey, and milk products except for fully fermented yogurt.
Low-Fermentable Oligo-Di-Monosaccharides and Polyol (FODMAP): Indigestible and slowly absorbed carbohydrates and short chained carbohydrates are reduced.
Mediterranean diet: composed of vegetables, fruits, legumes and nuts, grains, fish, excluding alcohol, milk, and red and processed meat.
What can we learn from the studies? Animal fat, red meat, and food additives were consistently associated with bad results. Some fruits, vegetables, fish, and soluble fiber were consistently associated with good results. Results with simple carbohydrates, dairy products, and grain were inconsistent. It seems appropriate to build a diet from these data.
In conclusion, Crohn’s Disease medications have been directed at anti-inflammatory agents (i.e. methyltrexate, prednisone and more recently anti-tumor necrosis factor alpha antibodies). Therapies designed to correct the genetic defects associated with Crohn’s disease are not anticipated in the near future. Current dietary recommendations deal primarily with the needs of those individuals with partial obstructive issues. There is little attention paid to dietary studies.
by Dr. Ralph Graff, MD