Fermentative dyspepsia revisited
A number of studies have investigated the composition of the intestinal flora using advanced molecular biological methods, and this is consistently thought to be altered in patients with irritable bowel syndrome compared with healthy persons (23). However, the findings are rela tively subtle and disappointingly inconsistent, and it is unclear whether the changes detected are primary or secondary to disruption of the intestinal function. In any case, from a pathophysiological perspective such studies of the structure of the intestinal flora provide relatively limited information – it is far more important to investigate what the microbes do than who they are.
The main function of the intestinal flora is to break down nutrients which the host is unable to digest itself (24). Food substances that are poorly absorbed in the small intestine, primarily low-digestible carbohydrates, continue to the colon, where they undergo microbial fermentation. Intriguingly, it is precisely this type of food that often gives rise to symptoms in patients with irritable bowel syndrome (25). This hypersensitivity to food has long been neglected, but is now being taken seriously, exemplified by the fact that the renowned American Journal of Gastroenterology recently dedicated an entire issue to a review of the disorder (26).
Intake of food with a high FODMAP content (fermentable oligosaccharides, disaccharides, monosaccharides and polyols) appears to play a central role in the development of symptoms (27). The Norwegian Directorate of Health now recommends that people with irritable bowel syndrome reduce their intake of these types of carbohydrates, which are found in large quantities in, for example, apples, fruit juice, wheat, broccoli, beans, milk and honey (28).
Interestingly, similar advice was given in the early 1900s in the treatment of fermentative dyspepsia (29). This diagnosis is no longer used, but it is worth noting that this old designation for irritable bowel syndrome expresses an essential aspect of the condition’s pathophysiology, namely that fermentation processes seem to be involved. We still know little about why fermentation provokes symptoms in people with irritable bowel syndrome (30), but we suspect that microbial metabolites may play a significant role (31). Perhaps this can explain both the gastrointestinal problems and the associated health symptoms (32)?