The theory behind the low-FODMAP diet does not take on the question of what causes IBS, rather it looks at the role that FODMAP-containing foods play in triggering digestive symptoms in people who suffer from visceral hypersensitivity and motility dysfunction. The FODMAP theory has been applied to both IBS and the inflammatory bowel diseases.
Why Do FODMAPs Cause Symptoms?
The acronym FODMAPs refers to Fermentable Oligo-, Di- and Mono-saccharides, and Polyols. FODMAP researchers have found that these short-chain carbohydrates and sugar alcohols are poorly absorbed by the small intestine and thus are rapidly set upon and fermented by bacteria within the digestive system, specifically the small intestine and the upper parts of the large intestine (proximal colon).
Researchers such as Peter Gibson at Monash University theorize that the rapid fermentation of these carbohydrates contributes to GI symptoms by creating a distention of the intestines in two ways—through a higher volume of liquid due to osmosis, and an increase in gas production.
The researchers have been conducting ongoing studies to support their theory. They have been looking at the volume of liquid produced by high FODMAPs foods (measured in individuals with ileostomies) and gas produced (measured by hydrogen breath testing) and have then been comparing these results to liquid and gas production of low FODMAPs foods.
This increase in intestinal distension brought about by high FODMAPs foods is thought to be a contributing factor in various IBS symptoms:
Abdominal pain Increased intestinal gas Bloating Abdominal distention Motility dysfunction that leads to diarrhea and constipation
How Does the Diet Help?
The FODMAP theory suggests that limiting the amount of high FODMAP foods should result in a decrease in these unpleasant digestive systems. FODMAP researchers are consistently finding that the low-FODMAP diet is effective in reducing symptoms in approximately three-quarters of IBS patients. Ongoing research is being conducted as to the accuracy of the components of this theory and the effectiveness of a low FODMAP diet in reducing digestive distress.
High FODMAP Foods
What foods are high in FODMAPs that you should avoid on this diet? Here is a quick list:
Fruits (and their juices) such as apples, apricots, blackberries, cherries, mango, nectarines, pears, plums, and watermelon. Fruit canned in natural fruit juice, dried fruit, or drinking large amounts of fruit juice. Vegetables such as artichokes, asparagus, beans, cabbage, cauliflower, garlic, lentils, mushrooms, onions, and peas. Dairy products including milk, soft cheeses, yogurt, custard, and ice cream Products made with wheat and rye High fructose corn syrup and honey. Candy and gum sweetened with non-sugar alcohol sweeteners: sorbitol, mannitol, xylitol, and maltitol.
Risks of a Low-FODMAP Diet
With so many nutritious foods included on the high FODMAP list, there is concern that people who try to avoid them will end up with a nutrient-deficient diet. It is wise to consult with a dietitian to find a balanced diet. Discuss this with your healthcare provider and see whether your healthcare provider has a plan you can follow or a dietitian who can assist you.
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