Normal bowel flora may play an important role in inflammatory bowel disease, including Crohn’s disease and ulcerative colitis. An article published in the Scandinavian Journal of Gastroenterology (2001; 36(Suppl 234): 29–40) reviewed the relationship between intestinal bacteria, immune tolerance, and intestinal permeability in these conditions.
The intestinal tract is essentially a long tube running from the mouth to the anus. Although it is part of the digestive system, the contents of the intestinal tract are technically still “outside” the body. The cells lining the intestine form a selective barrier that controls what is absorbed into the bloodstream and what remains within the gut.
When this barrier becomes compromised, intestinal permeability increases—a phenomenon sometimes referred to as “leaky gut.” According to the authors, increased permeability may lead to a breakdown in immune tolerance toward bacteria that normally reside in the intestine. Rather than peacefully coexisting with these microbes, the immune system may begin to react against them, potentially in an exaggerated or dysregulated manner. In addition, the composition of the intestinal bacteria appears to differ in patients with inflammatory bowel disease compared to healthy individuals.
Further evidence for this altered barrier function comes from research published in Gastroenterology (January 2002; 122(1): 44–54). In this study, colonoscopic biopsies from 305 patients with inflammatory bowel disease were compared with samples from 40 healthy controls. Patients with inflammatory bowel disease showed significantly higher concentrations of bacteria invading the intestinal mucosa than did the control group. In healthy individuals, the intestinal lining normally prevents bacteria from penetrating the mucosa; this protective function appeared to be impaired in those with inflammatory bowel disease.
The Scandinavian Journal of Gastroenterology review also noted that probiotic supplementation is sometimes helpful in this population. Patients with Crohn’s disease tend to have lower levels of Bifidobacteria and relatively higher levels of bacteria such as Bacteroides, Eubacteria, and Peptostreptococcus.
Probiotics are supplements containing living microorganisms that may help support digestive health. Common probiotic organisms include lactic acid–producing bacteria such as Lactobacillus species, Bifidobacteria (which appear to be reduced in Crohn’s disease), and certain Streptococcus species. These organisms may influence the intestinal environment by producing antimicrobial substances, lowering intestinal pH, supporting nutrient absorption, and interacting with immune signaling within the gut.
