Let’s Talk About the “P” in FODMAP
The “P” in FODMAP stands for polyols, but you may know them by another name – “sugar alcohols” – which is how they usually appear on the Nutrition Facts labels of packaged foods. The type of polyol/sugar alcohol found in a product, e.g., sorbitol or mannitol, can be found in the ingredients list.
The Chemistry of the “P” in FODMAP
Polyols are small-chain carbohydrates that occur naturally in certain fruits and vegetables or as additives in packaged foods. The two that have been extensively evaluated by the Monash University researchers who developed the low FODMAP diet are sorbitol and mannitol (you can see them on the Monash smartphone app).
What Causes Polyol Malabsorption?
Poyols are absorbed through pores in the small intestinal epithelium. This occurs slowly in all people, but the rate is influenced by factors that include polyol dose and type, gut transit time, size of the small intestinal epithelial pores, and the presence of intestinal disorders that reduce epithelial pore size, such as celiac disease.
Clearly, some people are predisposed to malabsorb these sugars due to factors that are not under their control, but just about everyone will experience digestive symptoms if they consume more than 10 to 20 grams of polyols at one time.
That’s why packaged foods that contain sorbitol and mannitol must include a warning that states, “Excess consumption may have a laxative effect.”
Polyols & Gut Symptoms
Similar to fructose, polyols attract water as they move through the small intestine by a process called osmosis. This occurs whether polyols are absorbed or not, but it can lead to pain and motility problems (typically, diarrhea) for people who are more sensitive to the pressure this fluid exerts on the intestinal walls.
Polyols that are not absorbed in the small intestine enter the large intestine where they are fermented by gut bacteria. The gas produced as a by-product of this bacterial fermentation distends the bowel, causing additional pain, bloating, and altered bowel habits in susceptible individuals.
Certain polyols (notably erythritol) are better tolerated than others because they are more efficiently absorbed in the small intestine. This reduces both the osmotic effect they exert in the small intestine and the amount of intact polyol molecules available for fermentation in the large intestine.
Testing for Polyol Malabsorption
Breath tests for sorbitol and mannitol malabsorption are available, but they are infrequently ordered. That’s actually a good thing since these tests are not particularly helpful as diagnostic tools.
For one thing, they’re not reproducible, i.e., you can get a positive result one day and a negative result soon after. Another downside to these tests is that the polyol dose used is often much larger than a person would typically consume in one sitting. More importantly, though, poyols can cause symptoms whether or not they are absorbed.
A more reliable way to find out if polyols are problematic for you is to initiate a polyol-restricted diet followed by a “test-to-tolerance” trial (like the Elimination and Challenge Phases of the low FODMAP diet).
An invaluable resource for those of you who choose this route is the Monash University FODMAP diet app, which lists the sorbitol and mannitol content of hundreds of foods.
Information about other polyols is not available on the app, but if you have trouble with sorbitol and mannitol you’ll probably need to limit most other poyols as well.
A quick way to identify additional polyols in the ingredients lists of packaged foods is to look for an “ol” ending, e.g., maltitol, xylitol, and lactitol; one polyol that bucks this trend is isomalt.
Food Sources of Polyols
Polyols are primarily found in stone fruits and as additives in sugar-free chewing gum, candy, and other low-cal or carb-free foods. They are also found in a number of fruits and vegetables.
Polyols are notorious for causing gastrointestinal symptoms if the amount consumed exceeds your absorptive capacity.
Packaged foods with added polyols are often of low nutritional value and ought to be avoided, but whole foods that contain these sugars should be kept in the diet if possible.
You can discover your personal comfort level for such foods using a systematic method like the three phases of the low FODMAP diet.