Monash University, Melbourne, Australia
There has been growing interest in the potential benefits of fructans (inulin [DP>10] and fructo-oligosaccharides [DP3-9]) in the ‘health’ of the human gastrointestinal tract. These compounds serve as storage carbohydrates and occur naturally in a wide variety of foods including onion, asparagus, artichoke, leek, wheat, garlic and chicory. Due to the nature of the fructosyl-fructose linkages, fructans are not digested or absorbed in the upper part of the gastrointestinal tract of humans and so reach the colon where they are rapidly fermented by the resident colonic microflora. Products of fermentation include short chain fatty acids and gases (hydrogen, methane, carbon dioxide). Other carbohydrates that are highly fermentable include stachyose, raffinose and poorly absorbed fructose, lactose and sugar alcohols (sorbitol, xylitol, mannitol). We have named this group of compounds FODMAPs - Fermentable Oligo-. Di- and Mono- saccharides and Polyols. Fructans join the growing number of carbohydrates to be manipulated and used by the food industry. Inulin and FOS (derived from inulin) are currently being added to a wide variety of processed foods. FOS and inulin stimulate the growth of beneficial microflora- bifidobacteria. Other putative health benefits range from improving calcium absorption to reducing the risk of colorectal cancer. We have, however, identified groups of patients with irritable bowel syndrome (IBS) and Crohn’s disease in which delivery of these highly fermentable carbohydrates to the distal small intestine and proximal colon may exacerbate their symptoms of abdominal pain, discomfort and irregular bowel habit. Dietary restrictions of fructans and other FODMAPs can relieve symptoms in 3 of 4 patients with IBS and is becoming the cornerstone of management of IBS symptoms. As one in six Australians over the age of 18 suffer from IBS more information is clearly required about the potential negative health impacts of these compounds.