Inflammatory Bowel Diseases
Inflammatory bowel diseases (IBDs) are characterized by chronic inflammation and diarrhea of the lower GI tract and include Crohn’s disease and ulcerative colitis. Crohn’s disease usually affects the small and large intestines, and less frequently the mouth, esophagus, and stomach, and causes damage that may extend through all layers of the gut wall. In contrast, ulcerative colitis involves the colon and the very end of the small intestine with tissue damage limited to the surface layers. IBDs usually present between 15 and 30 years of age and are now generally classified as autoimmune diseases with a genetic basis .
The pattern of ulcerations in Crohn’s disease is patchy, with normal tissue separated by diseased regions. Patients with Crohn’s disease may require surgical resection to remove affected areas, but new regions often become ulcerated.
The main consequence of Crohn’s disease is malnutrition resulting from intestinal resections as well as from impaired digestion and absorption. Reduced nutrient intake and eventual weight loss are common due to poor absorption of bile salts as a result of the interruption of the enterohepatic circulation. Thus, if the ileum is involved, bile acids may become depleted because of the loss of the active transport site for bile acids; this may cause malabsorption of fat, fat-soluble vitamins, calcium, magnesium, and zinc. Additionally, vitamin B12 deficiency can occur with ileal involvement, resulting in anemia.
The rectum is always involved in ulcerative colitis and lesions may extend into the colon. In mild cases, patients experience diarrhea and there may be weight loss, fever, and weakness, but in more severe forms, the disease is characterized by anemia, dehydration, electrolyte imbalance, and protein losses.
Dietary treatment for both Crohn’s disease and ulcerative colitis should aim at preventing symptoms associated with the diseases, correcting malnutrition, promoting healing of affected tissue, and enhancing normal growth and development in children. Approaches to nutritional therapy are variable and are based on individual symptoms, complications, and documented nutritional deficiencies. A high-calorie, high-protein diet is generally indicated, and adults with advanced disease may require 40 kcal/kg/day, or approximately 2.2 times the basal metabolic energy needs due to catabolic state and poor nutrient absorption . Nutritional supplements may be recommended, especially for children whose growth has been retarded. Special high-calorie liquid formulas are sometimes used for this purpose. A small number of patients may require periods of parenteral feeding to provide extra nutrition, allow the intestines to rest and hopefully heal, or to bypass the intestines for individuals whose guts cannot absorb enough nutrition from ingested food. Because of fat malabsorption, limiting fat intake may help, and medium-chain triglycerides may be better tolerated as they can be absorbed without the participation of bile salts. In some patients, a low-fiber diet may be indicated if there is a partial narrowing of the small intestine, while in others lactose restriction is to be recommended if the patient has proven lactose intolerance .
Prebiotics are nondigestible dietary oligosaccharides that affect the host by selectively stimulating growth, activity, or both of selective intestinal (probiotic) commensal bacteria. These bacteria may provide protection, stimulate local immune responses to combat infectious organisms, or suppress inflammation caused by antigens . Although more clinical studies need to be done, preliminary results from animal models and humans indicate that prebiotics and probiotics may provide effective treatments for people with IBD . There is evidence to support the use of probiotics in the treatment of pouchitis, a common problem among those who have had ileal pouch-anal anastomosis surgery for ulcerative colitis, and in ulcerative colitis, but not in Crohn’s disease .
There has been an explosion of these products in the market in recent years. They are added to dairy products, such as yogurt drinks, and are also sold in the form of capsules. The role of omega-3 fatty acids in the management of IBD is not clear. Results from some studies show they may have the potential to alleviate intestinal inflammation , but findings from other investigations do not support this anti-inflammatory role .