Fructose malabsorption

Fructose malabsorption
Other names	Dietary fructose intolerance
Chemical structure of fructose
Specialty	Endocrinology

Fructose malabsorption, formerly named dietary fructose intolerance (DFI), is a digestive disorder

Similarity in symptoms means that patients with fructose malabsorption often fit the profile of those with irritable bowel syndrome.[3]

Fructose malabsorption is not to be confused with

Fructose malabsorption may cause gastrointestinal symptoms such as abdominal pain, bloating, flatulence or diarrhea.^[4][5]

Pathophysiology

Fructose is absorbed in the small intestine without help of digestive enzymes. Even in healthy persons, however, only about 25–50 g of fructose per sitting can be properly absorbed. People with fructose malabsorption absorb less than 25 g per sitting.^[6] Simultaneous ingestion of fructose and sorbitol seems to increase malabsorption of fructose.^[7] Fructose that has not been adequately absorbed is fermented by intestinal bacteria producing hydrogen, carbon dioxide, methane and short-chain fatty acids.^[4][8] This abnormal increase in hydrogen may be detectable with the hydrogen breath test.^[7]

The physiological consequences of fructose malabsorption include increased osmotic load, rapid bacterial fermentation, altered

Restricting dietary intake of free fructose and/or fructans may provide symptom relief in a high proportion of patients with functional gut disorders.^[11]

Diagnosis

The diagnostic test, when used, is similar to that used to diagnose

Sitting down can cause your abdomen to compress, which slows down digestion. This can lead to issues such as bloating, heartburn and constipation.[12] It could thus increase or cause fructose malabsorption. A study show that physical activity between long periods of sitting is not enough: "focusing on acquiring the recommended dose of exercise is not a strong enough of a stimulant to completely protect the body from physical inactivity the other 23+ h/day".^[13] "Reducing prolonged overall sitting time may reduce metabolic disturbances"^[14]

Dietary supplements

There is no known cure, but an appropriate diet and the enzyme xylose isomerase can help.^[7] The ingestion of glucose simultaneously with fructose improves fructose absorption and may prevent the development of symptoms. For example, people may tolerate fruits such as grapefruits or bananas, which contain similar amounts of fructose and glucose, but apples are not tolerated because they contain high levels of fructose and lower levels of glucose.^[4] But a randomised controlled trials in patients with fructose malabsorption (made by the Cochrane institute) found that "Adding glucose to food and solutions to enhance fructose absorption is not effective in preventing fructose-induced functional gastrointestinal symptoms".^[16]

Foods that should be avoided by people with fructose malabsorption include:

• Foods and beverages containing greater than 0.5 g fructose in excess of glucose per 100 g and greater than 0.2 g of fructans per serving should be avoided. Foods with >3 g of fructose per serving are termed a 'high fructose load' and possibly present a risk of inducing symptoms. However, the concept of a 'high fructose load' has not been evaluated in terms of its importance in the success of the diet.^[17]
• Foods with high fructose-to-glucose ratio. Glucose enhances absorption of fructose, so fructose from foods with fructose-to-glucose ratio <1, like white potatoes, are readily absorbed, whereas foods with fructose-to-glucose ratio >1, like apples and pears, are often problematic regardless of the total amount of fructose in the food.^[18]
• Foods rich in
  leeks, onions, and wheat-containing products, including breads, cakes, biscuits, breakfast cereals, pies, pastas, pizzas, and wheat noodles
  .

The role that fructans play in fructose malabsorption is still under investigation. However, it is recommended that fructan intake for fructose malabsorbers should be kept to less than 0.5 grams/serving,[19] and supplements with inulin and fructooligosaccharide (FOS), both fructans, should be avoided.^[19]

• Foods containing artificial sweeteners like
  polyols (sugar alcohols, such as erythritol, mannitol
  and other ingredients that end with -tol, commonly added as in commercial foods).
• Foods containing
  high fructose corn syrup
  .

Foods with a high glucose content ingested with foods containing excess fructose may help patients absorb the excess fructose.[20]

Foods with high fructose content

According to the USDA database,^[21] foods with more fructose than glucose include:

The USDA food database reveals that many common fruits contain nearly equal amounts of the fructose and glucose, and they do not present problems for those individuals with fructose malabsorption.^[22] Some fruits with a greater ratio of fructose than glucose are apples, pears and watermelon, which contain more than twice as much fructose as glucose. Fructose levels in grapes varies depending on ripeness and variety, where unripe grapes contain more glucose.

Dietary guidelines for management

Researchers at Monash University in Australia developed dietary guidelines^[19] for managing fructose malabsorption, particularly for individuals with IBS.

Unfavorable foods (i.e. more fructose than glucose)

• Fruit –
  star fruit, watermelon
  ;
• Dried fruit – apple, currant,
  fig, pear, raisin, sultana
  ;
• Fortified wines
• Foods containing added sugars, such as
  agave nectar, some corn syrups
  , and fruit juice concentrates.

The following list of favorable foods was cited in the paper: "Fructose malabsorption and symptoms of Irritable Bowel Syndrome Guidelines for effective dietary management".[19] The fructose and glucose contents of foods listed on the Australian food standards^[23] would appear to indicate that most of the listed foods have higher fructose levels.

• nectarine, peach, plum (caution – these fruits contain sorbitol
  );
• Berry fruit: blackberry, boysenberry, cranberry, raspberry, strawberry, loganberry
  ;
• Citrus fruit: kumquat, grapefruit, lemon, lime, mandarin, orange, tangelo
  ;
• Other fruits: ripe
  passion fruit, pineapple, rhubarb, tamarillo
  .

Producers of processed food in most or all countries, including the US, are not currently required by law to mark foods containing "fructose in excess of glucose". This can cause some surprises and pitfalls for fructose malabsorbers.^[citation needed]

Foods (such as bread) marked "gluten-free" are usually suitable for fructose malabsorbers, though they need to be careful of gluten-free foods that contain dried fruit or high fructose corn syrup or fructose itself in sugar form. However, fructose malabsorbers do not need to avoid gluten, as those with celiac disease must.^{[citation needed]}

Many fructose malabsorbers can eat breads made from rye and corn flour. However, these may contain wheat unless marked "wheat-free" (or "gluten-free") (Note: Rye bread is not gluten-free.) Although often assumed to be an acceptable alternative to wheat, spelt flour is not suitable for people with fructose malabsorption^{[citation needed]}, just as it is not appropriate for those with wheat allergies or celiac disease. However, some fructose malabsorbers do not have difficulty with fructans from wheat products while they may have problems with foods that contain excess free fructose.^{[citation needed]}

There are many breads on the market that boast having no

Fructose and fructans are FODMAPs (fermentable oligo-, di- and mono-saccharides and polyols) known to cause gastrointestinal discomfort in susceptible individuals. FODMAPs are not the cause of these disorders,^[24] but FODMAPs restriction (a low-FODMAP diet) might help to improve short-term digestive symptoms in adults with irritable bowel syndrome (IBS) and other functional gastrointestinal disorders (FGID).^{[24][25][26][27]} Nevertheless, its long-term follow-up can have negative effects because it causes a detrimental impact on the gut microbiota and metabolome.^{[26][27][28][29]}

See also

• Hereditary fructose intolerance
• Food intolerance
• Gastroenterology
• Invisible disability

References