I have read that glucose aids in fructose absorption within the gut. Does this mean that theoretically, if one were to eat a high fructose problem food in combination with a high glucose starch, it may actually make the problem food more tolerable for the body than if each were eaten separately? For example, if pears or apples cause problems for one, if a potato or rice was eaten before or simultaneously with the food, would this theoretically, from a scientific standpoint, aid in the digestion and allow small portions of problem high fructose foods (ie apples, pears, honey), so long as they were accompanied by a predominantly glucose food? Is this a potential way to include small portions of these foods in the diet? I have not experimented with this yet, but I wondered if you could comment on the science behind the theory.
Thanks in advance, I.B.
Yes, adding some glucose (also known as dextrose) to a high fructose food should theoretically enhance fructose absorption and improve fructose tolerance to a degree that probably varies from one person to the next.
Update. November, 2015. At Gastrodiet 2015, PhD candidate Caroline Tuck shared some unpublished data that indicates despite its effect on enhancing fructose absorption, IBS symptoms reported by the 26 test subjects did not significantly improve when dextrose was added to the test dose of fructose. In other words, adding dextrose to fructose is not likely to be an effective coping strategy for people with IBS.
One of the mechanisms for fructose absorption in the small intestine requires an equal amount of glucose to be present in order to operate efficiently and move the fructose out of the gut and into the bloodstream. If there's no glucose around, the fructose gets stranded in the gut. That is why fruits with excess fructose relative to glucose are not suitable for low FODMAP diets.
Its not hard to buy glucose/dextrose and try for yourself whether adding some dextrose to high-fructose foods like fruit or honey will improves your tolerance. Tablets sold at the pharmacy for diabetics to raise their blood sugar quickly are made of dextrose. So are Smarties candies. You can buy dextrose in a jar for that matter from various supplement companies. How much dextrose would it take? Well, these foods vary in the exact ratio of fructose to glucose, but 5 grams of dextrose should more than cover the excess fructose in 1/2 cup of high-fructose fruit or a tablespoon of honey.
Cautions: Its not a magic bullet. Fructose absorption can be overwhelmed by too much fructose even when there is plenty of glucose around, so keep the portions small if you decide to experiment. Also, most high FODMAP fruits have both excess fructose and contain sugar alcohols. Adding glucose/dextrose won't do anything for polyol absorption, so if that's a problem too, symptoms could result. Also, if bacterial overgrowth is present, adding sugar in larger amounts might not be the best course of action, since bacteria in the small intestine can access them even before they are absorbed.