In a previous column I discussed Irritable Bowel Syndrome (IBS), which comes in two forms – IBS with diarrhea (IBS-D), which is more common in men, and IBS with constipation (IBS-C), more common in women. Symptoms (gas, bloating, cramps, and diarrhea) generally appear in young adulthood but may be diagnosed at any age. Symptoms can persist for decades and lead to life-style changes in many sufferers. As symptoms often appear after eating, traditional dietary advice has been to avoid large meals and reduce intake of fat, insoluble fibers, caffeine, spicy and gas-producing foods, and carbonated beverages. A gluten-free diet has also been advised as there is evidence of a relationship between IBS and celiac disease. Today I would like to share some relatively new dietary advice – a low FODMAP diet.
The term FODMAP was coined by researchers at Monash University in Australia. FODMAP stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. In other words FODMAPs are short-chain carbohydrates. Most of these compounds are slowly or poorly absorbed by the gut, or not absorbed at all making the gut contents more concentrated. A number of studies have shown that IBS symptoms are greatly improved after total elimination of FODMAPs for about four weeks followed by gradual re-introduction of them into the diet. Long-term use of a FODMAP-free diet is not recommended as it can adversely affect gut bacteria. Also, those with IBS-C may find symptoms slightly worsened because of decreased dietary fiber. They can use oat and rice bran as a fiber source instead.
So what are FODMAPs? Oligosaccharides include vegetables – artichokes, asparagus, beets, broccoli, Brussel sprouts, cabbage, fennel, garlic, leeks, okra, onions, peas, and shallots; fruits – watermelon, apple, white peaches, and persimmon; flour - wheat and rye; and legumes – chickpeas, lentils, kidney beans, baked beans, and soy beans. Disaccharides include milk (cow, goat, and sheep), yogurt, soft cheeses, custard, and ice cream. Monosaccharides include fruits – apples, pears, peaches, mango, sugar snap peas, watermelon, canned fruit in natural juice, concentrated fruit sources, and large servings of fruit, dried fruit, and fruit juice, honey, and sweeteners like fructose and high-fructose corn syrup (which seems to be in almost everything these days). Polyols include vegetables – avocados, cauliflower, mushrooms, snow peas, and sweet corn; fruits – apples, apricots, pears, cherries, nectarines, peaches, plums, prunes, and watermelon; and artificial sweeteners like isomalt, maltitol, mannitol, sorbitol, and xylitol.
While the above list may seem long, there are many non-FODMAP alternatives that can be used including other fruits and vegetables, lactose-free dairy products, maple syrup, and sucrose. In addition, probiotics are usually recommended for improving symptoms in IBS. Research has also shown that a low-FODMAP diet also improves symptoms in inflammatory bowel diseases like Crohn’s disease and ulcerative colitis. Someone planning to start a low-FODMAP diet should consult with a knowledgeable dietician as well as their physician (usually a gastroenterologist) as most physicians, perhaps with the exclusion of nutritionists, lack the formal knowledge and training in food composition.