Fructose is a simple sugar found in many foods, especially fruits, and in many packaged beverages and processed foods. Dietary intake of concentrated fructose has increased substantially over the last few decades overtaxing our ability to absorb it. Fructans are chains of fructose molecules found in fruits and some vegetables and grains, such as wheat and onions (see list below). Both fructose and fructans can cause problems.
Fructose Malabsorption Disorder (FM or FructMal) is the inability to absorb fructose and fructans. Two other less accurate names are: Fructose Intolerance and Dietary Fructose Intolerance. This condition is not to be confused with the rare disorder of hereditary fructose intolerance which can actually lead to death if not identified in early childhood.
FM is due to a deficiency of a protein in the small intestine. The function this protein is to grab a hold of fructose when it passes by, then pull the fructose into the intestinal lining for absorption. Lacking this protein, unabsorbed fructose continues on down into the large intestine where it feeds bacteria that create and release sizable amounts of hydrogen and methane. Initial negative gastrointestinal symptoms of FM generally show within a few hours of ingestion and take up to 3 days to resolve.
Unaddressed FM can lead to decreased nutrient absorption and deficiencies of: folic acid, tryptophan, glutathione (the most important amino acid for full body detoxification including heavy metals) and vitamins C and E causing a host of ailments both physical and mental.
What to do
You will need to avoid all fructose and fructans (see list below) for ten to fourteen days, however good results may show even within a few days. Occasionally the elimination needs to be longer, up to six weeks in rare cases to see results if your condition is really chronic. If a food or beverage tastes sweet and you are not sure, avoid it for the time being (carrot juice, rice milk, etc.). Once symptoms quiet down, you can begin slowly reintroducing eliminated foods, one to three a day, every day or two, using the lists below as a guide to find your level of tolerance. If you have a reaction, back away from the last foods introduced until symptoms quiet, then continue, minus the suspect offender(s). It is good to have a general understanding of the different types of sugars.
Disaccharide (two sugar combination)
Sucrose: (common names: table sugar, cane sugar, saccharose) composed of glucose and fructose. Generally well tolerated with FM
Lactose: milk sugar made from galactose and glucose. Often not well tolerated with FM, however fermented dairy products which lack lactose are likely well tolerated: aged cheese for example. You will want to avoid all milk products during the initial elimination trial in case lactose intolerance is part of your problem.
Monosaccharides (single sugar molecule)
Fructose: a simple sugar found in many foods which gets metabolized in the liver.
Glucose (also called dextrose or corn sugar) is made within the body for energy and stored as fat. Commercial glucose comes from corn starch and other plants. Glucose alone is readily absorbed, and sucrose, made of fructose and glucose, is generally well absorbed because of the glucose component. This means that fruits with higher glucose content will be more tolerable. Some people will take a glucose tablet after ingesting fructose and likely get by if it is just a little fruit, but this will not work if you have a whole piece of apple pie. While glucose will bind with fructose to aide absorption, it will not help with the absorption of fructans.
Sorbitol, Mannitol, Xylitol and the other ‘-ols’ inhibit fructose absorption and some of them contain fructose for a double whammy. So, if you have fructose with any of these ‘-ols’, symptoms will be worse.
After the Elimination
Once symptoms have quieted down, first try small servings of the less problematic foods due to a higher glucose to fructose ratio:
avocado, grapefruit, green beans, lemon, lime, raspberry, rhubarb, orange, pineapple, potato (peeling may help), strawberry, tomato paste, zucchini
artichoke, asparagus, beets, brown and wild rice, chicory, chocolate, garlic, granola, inulin, kamut, leek, legumes/beans, onion, parsnip, many protein bar products, soy products, spelt, sweet potato, wheat (sourdough bread is generally well tolerated because the fermentation process destroys the fructans)
If you tolerate the less problematic foods, go ahead and try some of the more problematic foods with high fructose to glucose ratio:
Agave, *apples, cherries, coconut milk, dried fruit, figs, grapes, guavas, honey, lychees, melons, mangos, maple syrup, molasses, paw-paws, *pears, peaches, persimmons, plums, prunes, raisins
* Worst offenders because they have both a high content of fructose, plus the fructose absorption inhibitor sorbitol.
Miscellaneous Fructose Tips
For many with FM, the concern is a cumulative one, with small occasional servings possibly being well tolerated especially when stress levels are low making for more effective digestion and absorption.
FM people often don’t tolerate probiotics such as acidophilus and bifidus and are particularly sensitive to prebiotics (nutrients which feed bacteria) such as fructo-oligosaccharides (FOS). If you are sensitive to probiotics then very likely you have FM.
Rye, oats, buckwheat, teff, millet, amaranth, tapioca flour, potato flour, corn flour and white rice seem to be fairly well tolerated with FM.
High fructose corn syrup (HFCS) is a ubiquitous additive in the food industry. Aside from being problematic with FM, it contains high levels of mercury. Young Americans consume about 70 grams a day of HFCS containing about 40mcg of mercury which is 10 times the reference range considered safe. It is also a common cause of non-alcoholic fatty liver. HFCS should be taken off the market.
Aside from FM, most Americans consume concentrated fructose at levels far beyond what the body can handle contributing to obesity, heart disease and diabetes.
Cooking and freezing may alter fructose content, increasing or decreasing the impact.
For those reluctant to try the elimination method which is the most reliable and free, I suggest the Breath Test. This test evaluates for respired levels of hydrogen and methane following ingestion of fructose.
If you are one of those with bowel problems unimproved by milk and wheat family avoidance, fructose may well be the culprit. Problems with fructose are becoming more common because fructose concentrates which lack glucose for balance are being used more and more by the food industry. Identifying fructose malabsorption problems is crucial when trying to address IBS type concerns as well as multiple mental and emotional issues which are so common these days.
I hope you have enjoyed this month’s newsletter. Comments as always are welcome.
Jon Dunn, ND