Principles of a Diet in Fructose Malabsorption
Individuals with fructose malabsorption (FM) may experience gastrointestinal symptoms, like diarrhea and bloating, after ingesting fructose, sorbitol, fructans, or otherFODMAPs in an amount exceeding their absorption threshold (1).
Fructose absorption threshold in FM may range from 0 to 25 grams of fructose per sitting (1).
Foods to avoid in FM:
- Fructose-rich foods, foods with high fructose-to-glucose ratio, or any fructose-containing food in large amount
- Foods with high fructose corn syrup (HFCS)
- Foods rich in sorbitol
- Foods rich in fructans or other FODMAPs – problematic only in some persons with FM
Tolerance threshold for fructose in most healthy persons is 25-50 g of fructose per sitting, but in a person with FM is lower than 25 g. Tolerance threshold for sorbitol in a sensitive person may be as low as 10g of sorbitol per sitting. When fructose and sorbitol (or other FODMAPs) are combined in one food, relatively lower amount of each may cause symptoms.
Glucose enhances absorption of fructose, so moderate amount of foods with equal or lower amounts of fructose than glucose (like table sugar, bananas) should be OK…if they do not contain sorbitol (1).
Ingesting fructose-containing foods together with other foods may help, because this way fructose is released from the stomach slower and delivered to the small intestine in a longer period of time, what enables better fructose absorption.
Fructose is a simple sugar (monosaccharide) naturally appearing in honey, fruits and many vegetables. It is a part of table sugar (sucrose), other sugars and syrups, like high fructose corn syrup (HFCS) that is often added to commercial foods as anartificial sweetener. HFCS does not naturally appear in animal foods.
On labels of commercial foods, fructose may be referred as fructose,or fruit sugar. Fructose is a part of high fructose corn syrup (HFCS), corn syrup solids, fruit juice concentrate, fructose-glucose syrup, corn sweeteners, honey, invert sugar, maple sugar, maple syrup, molasses, Turbinado, and other sugars and syrups.
Sucrose (table or white sugar) is a disaccharide that contains equal parts of glucose and fructose, and is found naturally in sugar cane, sugar beets, fruits and many vegetables. It is often used as a sweetener in commercial foods.
Sucrose is well tolerated by many persons with fructose malabsorption, if taken in moderation.
Fructose-to-Glucose Ratio (F:G)
One molecule of glucose enhances absorption of one molecule of fructose in the small intestine. This explains why many persons with FM can safely eat foods high in fructose, if they contain at least the same amount of glucose. For example, sugar (50 g fructose, 50 g glucose, F:G = 1) in a moderate amount is often well tolerated in FM, since all fructose is absorbed by the help of glucose. On the other hand, foods with only a moderate amount of fructose, but low in glucose (pears: 6,23 g fructose, 2,76 g glucose, F:G = 2,76 ) regularly cause diarrhea and bloating, since some fructose has no glucose aid in absorption.
High Fructose Corn Syrup (HFCS)
HFCS-55 is a liquid solution containing 55% fructose and 45% glucose in dry matter. It became a popular artificial sweetener, since less of it is needed to achieve the same sweetness as sugar has, it blends with drinks and foods, it prolongs shelf life of foods, and its production is cheep.
HFCS may be present in soft, fruit and sports drinks, candies, jams, yogurts, condiments, canned and packaged foods, and other sweetened foods. HFCS-42 (42% fructose, 58% glucose) easily blends with foods, so it is often used to sweaten baked products.
HFCS regularly causes diarrhea/bloating in many persons with FM.
Sorbitol (C6H14O6), also named glucitol, is a sugar alcohol (polyol) derived from glucose. It is used as an artificial sweetener in diet soda, sugar free chewing gum, other sweetened products, or as a moisture stabiliser in baked products. On labels it can be referred as humectant, sweetener, emulsifier, it may be ‘hidden’ in sugar alcohols (polyols), or denoted as E420. It may be present in medical syrups for children, and it is also used as a laxative.
Sorbitol naturally occurs in stone fruits (plums, peaches, apricots, cherries, etc), apples, pears, grapes, and may appear in high amounts in dried fruits, like prunes, raisins, figs etc. It also appear in related fruit juices, jams, etc (foods high in sorbitol) (9,10). Sorbitol is partly absorbed in the small intestine – it’s calorie value is 2.6 calories/g (sugar has 4 cal/g).
Sorbitol seems to slow absorption of fructose. If ingested in excess, it drags water into intestine and causes osmotic diarrhea; 10g of sorbitol (1 stick of chewing gum contains ~ 1.25g of sorbitol) can cause prominent diarrhea in a child. Consuming 20g of sorbitol daily was reported to cause chronic diarrhea and weight loss in adult. Persons with fructose malabsorption are often excessively sensitive to sorbitol.
Fructans are short chains of fructose with a glucose molecule on the end. Fructans themselves cannot be absorbed in the human gut, but they interfere with fructose absorption and may (only in sensitive persons and in a considerable amount) cause the same symptoms as fructose or sorbitol. They mostly appear in wheat, onions, asparagus, artichokes, leeks and chicory. On labels, fructans may be referred as inulin, fructo-oligo-saccharide (FOS), or oligofructose.
FODMAP stands for Fermentable Oligo-, Di- and Mono-saccharides And Polyols. They are often poorly absorbed in persons with FM, so they aggravate MF symptoms.
FODMAPs appear in:
- Beans, cabbage, Brussels sprouts, broccoli, asparagus, and whole grains (raffinose, galactose, fructans)
- Dairy products (lactose)
- Beer, malt (maltose)
- Fruits, vegetables (fructose)
- Stone fruits, berries (sorbitol, xylitol)
- Sweetened commercial products (polyols: sorbitol, mannitol, xylitol, isomalt, maltitol, arabitol, erythritol, glycol, glycerol, lactitol, ribitol)
On labels, FODMAPs appear under carbohydrates, sugars or polyols. Read about low-FODMAP diet.
A Low-Fructose Diet Trial
Three days of strict low-fructose (and sorbitol) diet should result in obvious lessening of symptoms in most individuals with fructose malabsorption.
To find out, if you have fructose malabsorption, follow these steps:
- Exclude all fruits, vegetables (and related products), table sugar, honey, and anything containing fructose, sugar, or sorbitol from your meals for 3 days (72 hours).
- If your symptoms obviously lessen in this time, it is possible you have fructose malabsorption. Continue with the same diet for 6 weeks. In this time your fructose absorption threshold may somewhat increase and later you might be able to add some foods low in fructose.
- If symptoms does not lessen in 3 days, or do but only a little, prolong the diet trial for the next three days and additionally exclude all foods with fructans (wheat, artichokes, asparagus, leeks, chicory).
- If still no improvement, continue with FODMAP diet for the next 3 days – exclude all dairy products, legumes (beans, peas, soy), cauliflower, Brussels sprout and cabbage.
If no success, arrange an appointment with a gastroenterologist, and ask for a hydrogen breath test with fructose, which is an official and reliable test for fructose malabsorption.
If symptoms do not improve after 6-8 weeks of low-fructose diet, other diagnoses, like lactose intolerance, small intestinal bacterial overgrowth (SIBO) , celiac disease, and Hereditary Fructose Intolerance (HFI) should be considered.
University of Iowa low fructose recipes
Fructose-Free Diet (in HFI)
Persons with hereditary fructose intolerance (HFI) should not ingest any fructose, or substances which yield fructose, such as sucrose and sorbitol. Registered nutritionist should be consulted to get reliable lists of fructose/sucrose/sorbitol -free foods.
- Nutrition Guide: Foods, Safe to Eat, to Try, or to Avoid in FM
- List of Foods, High in Fructose, Sorbitol, Fructans, Polyols, FODMAPs
- Fructose malabsorption and FODMAPs (virginia.edu)