I found out about fructose malabsorption by reading the IBS research literature. In consultation with a GP I tried an elimination diet and found that I had problems with the sugars fructose, lactose and sorbitol. There is a breath test but unfortunately the fructose test does not tell you how much excess fructose (i.e more fructose than glucose) you can tolerate. The test is done using a 30 gram load of fructose. So while you may test positive at that load the test doesn't tell you if you can handle 1, 5, 10, etc excess grams of fructose. You still have to experiment to figure it out. A recent study shows that about 45-55% of IBSers have problems with fructose.
Fructose malabsorption can also include problems with wheat which contain fructans. Fructans are long chains of fructose molecules that are indigestible in the stomach or small intestine. However, they are easily fermentable by bacteria in the colon. Generally speaking wheat doesn't have to be eliminate from the diet but its consumption reduced.
Fructose, fructan, sorbitol, lactose, etc are known as short-chained carbohydrates. Collectively they are called FODMAPs (Fermentable Oligo-, Di- and Mono-saccharides And Polyols). Beside the article linked to in my signature there is a good article on FODMAPS in Malabsorption of Fructose and Other Short-chain Carbohydrates
Soy is a problem for a lot of IBSers and normal people too. It can produce cramping and gas. I cannot eat it even in small quantities which annoys me because I love soy sauce on rice. Some people find they can eat soy if they take Beano.
Over the years I have learned that dietary supplement and some digestive enzymes can cause problems. Some of them contain ground up plant material containing the active ingredient. Unfortunately, they also contain a high amount of insoluble fiber which can cause problems. Also, most digestive enzymes which are composed or proteins are broken down in the stomach acid providing little benefit. However, the enzyme in Beano and lactase are two digestive enzymes that do work well.
I find many herbal teas are problematic. Not sure why.
Generally speaking food allergy tests will not enlighten you much. From the IBS research I have read an food elimination approach is more effective that an allergy test.
While eliminating a variety of foods from your diet may help manage IBS symptoms it is definitely not the definitive answer. Dietary management helps me keep my IBS enough under control that I can 'almost' live an ordinary life but I still have bloating and pain daily --- it is just not as intense
I completely understand your frustration. I am sure most people with IBS ask themselves the same questions you do daily. You would figure the medical profession would have figured out how to manage or cure IBS by now. However, the GI systems is one of the most complicated organs in the body. It is an interface between the outside world and our internal workings. Surprisingly we still know relatively little about how it functions
Have you tried to figure out a base diet - that is a simple diet to which can fall back on when you get an IBS flare-up?
-------------------- STABLE: ♂, IBS-D 50+ years - Science of IBS