Fructose malabsorption, formerly named "dietary
fructoseFructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
intolerance," is a digestive disorder in which absorption of fructose is impaired by deficient fructose carriers in the small intestine's
enterocyteEnterocytes, or intestinal absorptive cells, are simple columnar epithelial cells found in the small intestines and colon. A glycocalyx surface coat contains digestive enzymes. Microvilli on the apical surface increase surface area for the digestion and transport of molecules from the intestinal...
s. This results in an increased concentration of
fructoseFructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
in the entire intestine.
Fructose malabsorption is found in up to 30% of the population of Western countries and Africa. Some estimates for Asia seem to be considerably lower but are still at 10% of the population.
This condition is common in patients identified to be suffering
symptomA symptom is a departure from normal function or feeling which is noticed by a patient, indicating the presence of disease or abnormality...
s of
irritable bowel syndromeIrritable bowel syndrome is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements...
, although occurrence in these patients is not higher than occurrence in the normal population. Conversely, patients with fructose malabsorption often fit the profile of those with irritable bowel syndrome. A small proportion of patients with both fructose malabsorption and
lactose intoleranceLactose intolerance, also called lactase deficiency or hypolactasia, is the inability to digest and metabolize lactose, a sugar found in milk...
also suffer from celiac disease.
Fructose malabsorption is not to be confused with hereditary fructose intolerance, a potentially fatal condition in which the liver enzymes that break up fructose are deficient.
Pathophysiology
Fructose is absorbed in the small intestine without help of digestive enzymes. Even in healthy persons, however, only about 25-50g of fructose per sitting can be properly absorbed. Persons with fructose malabsorption may absorb less than 25g per sitting (NB: Amount is arbitrarily determined according to investigation of fructose absorption in many individuals). In the large intestine, fructose that hasn't been adequately absorbed osmotically reduces the absorption of water and is metabolized by normal colonic bacteria to short chain fatty acids and the gases hydrogen, carbon dioxide and methane. This abnormal increase in hydrogen is detectable with the
hydrogen breath testA hydrogen breath test is used as a clinical medical diagnosis for people with irritable bowel syndrome, and common food intolerances. The test is simple, non-invasive, and is performed after a short period of fasting . Even though the test is normally known as a "Hydrogen Breath Test" some...
.
The physiological consequences of fructose malabsorption include increasing osmotic load, providing substrate for rapid bacterial fermentation, changing gastrointestinal motility, promoting mucosal
biofilmA biofilm is an aggregate of microorganisms in which cells adhere to each other on a surface. These adherent cells are frequently embedded within a self-produced matrix of extracellular polymeric substance...
and altering the profile of bacteria. These effects are additive with other short-chain poorly absorbed carbohydrates such as
sorbitolSorbitol, also known as glucitol, Sorbogem® and Sorbo®, is a sugar alcohol that the human body metabolizes slowly. It can be obtained by reduction of glucose, changing the aldehyde group to a hydroxyl group. Sorbitol is found in apples, pears, peaches, and prunes...
. The clinical significance of these events depends upon the response of the bowel to such changes; they have a higher chance of inducing symptoms in people with functional gut disorders than asymptomatic subjects. Some effects of fructose malabsorption are decreased
tryptophanTryptophan is one of the 20 standard amino acids, as well as an essential amino acid in the human diet. It is encoded in the standard genetic code as the codon UGG...
,
folic acidFolic acid and folate , as well as pteroyl-L-glutamic acid, pteroyl-L-glutamate, and pteroylmonoglutamic acid are forms of the water-soluble vitamin B9...
and
zincZinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
in the blood.
Restricting dietary intake of free fructose and/or fructans may provide symptom relief in a high proportion of patients with functional gut disorders.
Symptoms
- Bloating
Bloating is any abnormal general swelling, or increase in diameter of the abdominal area. As a symptom, the patient feels a full and tight abdomen, which may cause abdominal pain sometimes accompanied by increased borborygmus or more seriously the total lack of borborygmus.-Symptoms:The most common...
(from fermentation in the small and large intestine)
- Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...
and/or constipationConstipation refers to bowel movements that are infrequent or hard to pass. Constipation is a common cause of painful defecation...
- Flatulence
Flatulence is the expulsion through the rectum of a mixture of gases that are byproducts of the digestion process of mammals and other animals. The medical term for the mixture of gases is flatus, informally known as a fart, or simply gas...
- Stomach
The stomach is a muscular, hollow, dilated part of the alimentary canal which functions as an important organ of the digestive tract in some animals, including vertebrates, echinoderms, insects , and molluscs. It is involved in the second phase of digestion, following mastication .The stomach is...
pain (as a result of muscle spasmIn medicine a spasm is a sudden, involuntary contraction of a muscle, a group of muscles, or a hollow organ, or a similarly sudden contraction of an orifice. It is sometimes accompanied by a sudden burst of pain, but is usually harmless and ceases after a few minutes...
s, the intensity of which can vary from mildMild may mean:*Mild ale, often simply referred to as mild, from the Old English milde, meaning "young" or "immature"*Håkan Mild , Swedish former footballer and current director of sports of IFK Göteborg...
and chronicA chronic disease is a disease or other human health condition that is persistent or long-lasting in nature. The term chronic is usually applied when the course of the disease lasts for more than three months. Common chronic diseases include asthma, cancer, diabetes and HIV/AIDS.In medicine, the...
to acute but erraticErratic can refer to:* Erratic, a project of music artist Jan Robbe* Glacial erratic, is a piece of rock that differs from the size and type of rock native to the area in which it rests* Erratic ant, a species...
)
- Vomiting
Vomiting is the forceful expulsion of the contents of one's stomach through the mouth and sometimes the nose...
(if great quantities are consumed)
- Early signs of mental depression
Depression is a state of low mood and aversion to activity that can affect a person's thoughts, behaviour, feelings and physical well-being. Depressed people may feel sad, anxious, empty, hopeless, helpless, worthless, guilty, irritable, or restless...
Other symptoms include:
- aching eyes
- fuzzy head
- fatigue
Diagnosis
The diagnostic test, when used, is similar to that used to diagnose
lactose intoleranceLactose intolerance, also called lactase deficiency or hypolactasia, is the inability to digest and metabolize lactose, a sugar found in milk...
. It is called a
hydrogen breath testA hydrogen breath test is used as a clinical medical diagnosis for people with irritable bowel syndrome, and common food intolerances. The test is simple, non-invasive, and is performed after a short period of fasting . Even though the test is normally known as a "Hydrogen Breath Test" some...
and is the method currently used for a clinical
diagnosisMedical diagnosis refers both to the process of attempting to determine or identify a possible disease or disorder , and to the opinion reached by this process...
.
Diet
Foods that should be avoided by people with fructose malabsorption include:
- Foods and beverages containing greater than 0.5g fructose in excess of glucose per 100g and greater than 0.2g of fructans per serving should be avoided. Foods with >3g 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.
- Foods with high fructose-to-glucose ratio. Glucose enhances absorption of fructose, so fructose from foods with fructose-to-glucose ratio <1, like banana
Banana is the common name for herbaceous plants of the genus Musa and for the fruit they produce. Bananas come in a variety of sizes and colors when ripe, including yellow, purple, and red....
s, is 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.
- Foods rich in fructans and other Fermentable Oligo-, Di- and Mono-saccharides and Polyols (FODMAPs), including artichoke
-Plants:* Globe artichoke, a partially edible perennial thistle originating in southern Europe around the Mediterranean* Jerusalem artichoke, a species of sunflower with an edible tuber...
s, asparagusAsparagus officinalis is a spring vegetable, a flowering perennialplant species in the genus Asparagus. It was once classified in the lily family, like its Allium cousins, onions and garlic, but the Liliaceae have been split and the onion-like plants are now in the family Amaryllidaceae and...
, leeks, onionThe onion , also known as the bulb onion, common onion and garden onion, is the most widely cultivated species of the genus Allium. The genus Allium also contains a number of other species variously referred to as onions and cultivated for food, such as the Japanese bunching onion The onion...
s , and wheatWheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
-containing products, including most beerBeer is the world's most widely consumed andprobably oldest alcoholic beverage; it is the third most popular drink overall, after water and tea. It is produced by the brewing and fermentation of sugars, mainly derived from malted cereal grains, most commonly malted barley and malted wheat...
s, breadBread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...
s, cakeCake is a form of bread or bread-like food. In its modern forms, it is typically a sweet and enriched baked dessert. In its oldest forms, cakes were normally fried breads or cheesecakes, and normally had a disk shape...
s, biscuitA biscuit is a baked, edible, and commonly flour-based product. The term is used to apply to two distinctly different products in North America and the Commonwealth Nations....
s, breakfast cerealA breakfast cereal is a food made from processed grains that is often, but not always, eaten with the first meal of the day. It is often eaten cold, usually mixed with milk , water, or yogurt, and sometimes fruit but sometimes eaten dry. Some cereals, such as oatmeal, may be served hot as porridge...
s, pieA pie is a baked dish which is usually made of a pastry dough casing that covers or completely contains a filling of various sweet or savoury ingredients....
s, pastaPasta is a staple food of traditional Italian cuisine, now of worldwide renown. It takes the form of unleavened dough, made in Italy, mostly of durum wheat , water and sometimes eggs. Pasta comes in a variety of different shapes that serve for both decoration and to act as a carrier for the...
s, pizzaPizza is an oven-baked, flat, disc-shaped bread typically topped with a tomato sauce, cheese and various toppings.Originating in Italy, from the Neapolitan cuisine, the dish has become popular in many parts of the world. An establishment that makes and sells pizzas is called a "pizzeria"...
s, and some noodleThe noodle is a type of food, made from any of a variety of doughs, formed into long thin ribbons, strips, curly-cues, waves, helices, pipes, tubes, strings, or other various shapes, sometimes folded. They are usually cooked in a mixture of boiling water and/or oil. Depending upon the type, noodles...
s.
- Foods containing sorbitol
Sorbitol, also known as glucitol, Sorbogem® and Sorbo®, is a sugar alcohol that the human body metabolizes slowly. It can be obtained by reduction of glucose, changing the aldehyde group to a hydroxyl group. Sorbitol is found in apples, pears, peaches, and prunes...
, present in some diet drinks and foodsDiet food refers to any food or drink whose recipe has been altered in some way to make it part of a body modification diet...
, and occurring naturally in some stone fruits, or xylitolXylitol is a sugar alcohol sweetener used as a naturally occurring sugar substitute. It is found in the fibers of many fruits and vegetables, and can be extracted from various berries, oats, and mushrooms, as well as fibrous material such as corn husks and sugar cane bagasse, and birch...
, present in some berries, and other polyols (sugar alcohols), such as erythritol, mannitol, and other ingredients that end with -tol, commonly added as artificial sweeteners in commercial foods.
Foods with a high glucose content ingested with foods containing excess fructose may help sufferers absorb the excess fructose.
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, and supplements with
inulinInulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
and
fructooligosaccharideFructooligosaccharides also sometimes called oligofructose or oligofructan, are oligosaccharide fructans, used as an alternative sweetener. FOS exhibits sweetness levels between 30 and 50 percent of sugar in commercially-prepared syrups...
(FOS), both fructans, should be avoided.
Foods with high fructose content
According to the USDA database, foods with more fructose than glucose include:
| Food |
Fructose (grams / 100 grams) |
Glucose (grams / 100 grams) |
| Sucrose Sucrose is the organic compound commonly known as table sugar and sometimes called saccharose. A white, odorless, crystalline powder with a sweet taste, it is best known for its role in human nutrition. The molecule is a disaccharide composed of glucose and fructose with the molecular formula...
(for reference) |
50 |
50 |
AppleThe apple is the pomaceous fruit of the apple tree, species Malus domestica in the rose family . It is one of the most widely cultivated tree fruits, and the most widely known of the many members of genus Malus that are used by humans. Apple grow on small, deciduous trees that blossom in the spring...
s |
5.9 |
2.4 |
PearThe pear is any of several tree species of genus Pyrus and also the name of the pomaceous fruit of these trees. Several species of pear are valued by humans for their edible fruit, but the fruit of other species is small, hard, and astringent....
s |
6.2 |
2.8 |
Fruit juice
e.g. Apples,
Pears |
5 to 7 |
2 to 3 |
WatermelonWatermelon is a vine-like flowering plant originally from southern Africa. Its fruit, which is also called watermelon, is a special kind referred to by botanists as a pepo, a berry which has a thick rind and fleshy center...
|
3.4 |
1.6 |
RaisinRaisins are dried grapes. They are produced in many regions of the world. Raisins may be eaten raw or used in cooking, baking and brewing...
s |
29.8 |
27.8 |
| Honey Honey is a sweet food made by bees using nectar from flowers. The variety produced by honey bees is the one most commonly referred to and is the type of honey collected by beekeepers and consumed by humans...
|
40.9 |
35.7 |
High fructose
corn syrupHigh-fructose corn syrup — also called glucose-fructose syrup in the UK, glucose/fructose in Canada, and high-fructose maize syrup in other countries — comprises any of a group of corn syrups that has undergone enzymatic processing to convert some of its glucose into fructose to produce...
|
42 to 55 |
45 to 58 |
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. 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 the management of fructose malabsorption
Researchers at Monash University in Australia developed dietary guidelines for managing fructose malabsorption, particularly for individuals with IBS.
Unfavorable foods (i.e. more fructose than glucose)
- Fruit — apple, pear, guava, honeydew melon, nashi fruit, pawpaw, papaya, quince, star fruit, watermelon;
- Dried fruit - apple, currant, date, fig, pear, raisin, sultana;
- Fortified wines
- Foods containing added sugars, such as agave nectar, some corn syrups, and fruit juice concentrates.
Favorable foods (i.e. fructose equal to or less than glucose)
- Stone fruit: apricot, nectarine, peach, plum (caution - these fruits contain sorbitol);
- Berry fruit: blueberry, blackberry, boysenberry, cranberry, raspberry, strawberry, loganberry;
- Citrus fruit: kumquat, grapefruit, lemon, lime, mandarin, orange, tangelo;
- Other fruits: ripe banana, jackfruit, kiwi fruit, passion fruit, pineapple, rhubarb, tamarillo.
United States Food-labeling laws
Producers of processed food in the USA 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.
Foods (such as
breadBread is a staple food prepared by cooking a dough of flour and water and often additional ingredients. Doughs are usually baked, but in some cuisines breads are steamed , fried , or baked on an unoiled frying pan . It may be leavened or unleavened...
) marked "gluten-free" are usually suitable for fructose malabsorbers, though sufferers need to be careful of gluten-free foods that contain
dried fruitDried fruit is fruit where the majority of the original water content has been removed either naturally, through sun drying, or through the use of specialized dryers or dehydrators. Dried fruit has a long tradition of use dating back to the fourth millennium BC in Mesopotamia, and is prized...
or high fructose corn syrup or
fructoseFructose, or fruit sugar, is a simple monosaccharide found in many plants. It is one of the three dietary monosaccharides, along with glucose and galactose, that are absorbed directly into the bloodstream during digestion. Fructose was discovered by French chemist Augustin-Pierre Dubrunfaut in 1847...
itself in sugar form. However, fructose malabsorbers do
not need to avoid
glutenGluten is a protein composite found in foods processed from wheat and related grain species, including barley and rye...
, as those with
celiac diseaseCoeliac disease , is an autoimmune disorder of the small intestine that occurs in genetically predisposed people of all ages from middle infancy onward...
must.
Many fructose malabsorbers can eat breads made from
ryeRye is a grass grown extensively as a grain and as a forage crop. It is a member of the wheat tribe and is closely related to barley and wheat. Rye grain is used for flour, rye bread, rye beer, some whiskeys, some vodkas, and animal fodder...
and
cornMaize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
flour. However, these may contain
wheatWheat is a cereal grain, originally from the Levant region of the Near East, but now cultivated worldwide. In 2007 world production of wheat was 607 million tons, making it the third most-produced cereal after maize and rice...
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 sufferers of fructose malabsorption, just as it is not appropriate for those with
wheat allergiesWheat allergy is a food allergy, but can also be a contact allergy resulting from occupational exposure. Like all allergies wheat allergy involves IgE and mast cell response. Typically the allergy is limited to the seed storage proteins of wheat, some reactions are restricted to wheat proteins,...
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.
There are many breads on the market that boast having no
high fructose corn syrupHigh-fructose corn syrup — also called glucose-fructose syrup in the UK, glucose/fructose in Canada, and high-fructose maize syrup in other countries — comprises any of a group of corn syrups that has undergone enzymatic processing to convert some of its glucose into fructose to produce...
. In lieu of high fructose corn syrup, however, one may find the production of special breads with a high inulin content, where
inulinInulins are a group of naturally occurring polysaccharides produced by many types of plants. They belong to a class of fibers known as fructans. Inulin is used by some plants as a means of storing energy and is typically found in roots or rhizomes...
is a replacement in the
baking processBaking is the technique of prolonged cooking of food by dry heat acting by convection, and not by radiation, normally in an oven, but also in hot ashes, or on hot stones. It is primarily used for the preparation of bread, cakes, pastries and pies, tarts, quiches, cookies and crackers. Such items...
for the following: high fructose corn syrup,
flourFlour is a powder which is made by grinding cereal grains, other seeds or roots . It is the main ingredient of bread, which is a staple food for many cultures, making the availability of adequate supplies of flour a major economic and political issue at various times throughout history...
and
fatFats consist of a wide group of compounds that are generally soluble in organic solvents and generally insoluble in water. Chemically, fats are triglycerides, triesters of glycerol and any of several fatty acids. Fats may be either solid or liquid at room temperature, depending on their structure...
. Because of the caloric reduction, lower fat content, dramatic fiber increase and prebiotic tendencies of the replacement inulin, these breads are considered a healthier alternative to traditionally prepared leavening breads. Though the touted health benefits may exist, sufferers of fructose malabsorption will likely find no difference between these new breads and traditionally prepared breads in alleviating their symptoms because inulin is a
fructanA fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides, whereas longer chain fructans are termed inulins...
, and, again, consumption of fructans should be reduced dramatically in those with fructose malabsorption in an effort to appease symptoms.
New research
Fructose and
fructanA fructan is a polymer of fructose molecules. Fructans with a short chain length are known as fructooligosaccharides, whereas longer chain fructans are termed inulins...
s which are polymers of fructose are FODMAPs (Fermentable Oligo-, Di- and Mono-saccharides and Polyols) known to cause GI discomfort in susceptible individuals. A low FODMAP diet has widespread application for managing functional GI disorders such as
IBSIrritable bowel syndrome is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements...
and
IBDIn medicine, inflammatory bowel disease is a group of inflammatory conditions of the colon and small intestine. The major types of IBD are Crohn's disease and ulcerative colitis.-Classification:...
.
See also
- Gastroenterology
Gastroenterology is the branch of medicine whereby the digestive system and its disorders are studied. The name is a combination of three Ancient Greek words gaster , enteron , and logos...
- Hydrogen breath test
A hydrogen breath test is used as a clinical medical diagnosis for people with irritable bowel syndrome, and common food intolerances. The test is simple, non-invasive, and is performed after a short period of fasting . Even though the test is normally known as a "Hydrogen Breath Test" some...
- Invisible disability
Invisible disabilities are disabilities that are not immediately apparent. Some people with visual or auditory disabilities who do not wear glasses or hearing aids, or discreet hearing aids, may not be obviously disabled. Some people who have vision loss may wear contacts...
- Food intolerance
Food intolerance or non-allergic food hypersensitivity is a term used widely for varied physiological responses associated with a particular food, or compound found in a range of foods....
- Irritable bowel syndrome
Irritable bowel syndrome is a diagnosis of exclusion. It is a functional bowel disorder characterized by chronic abdominal pain, discomfort, bloating, and alteration of bowel habits in the absence of any detectable organic cause. In some cases, the symptoms are relieved by bowel movements...
- Malabsorption
Malabsorption is a state arising from abnormality in absorption of food nutrients across the gastrointestinal tract.Impairment can be of single or multiple nutrients depending on the abnormality...
External links