Fructose Intolerance


Fructose intolerance is a condition in which the body has difficult digesting fructose and fructose-containing foods. It is treated by complete elimination of fructose and sucrose from the diet.

Sugars and sweeteners


Not tolerated


Agave syrup

Barley malt syrup

Baker's sugar

Birch sugar (if pure)

Beet sugar

Corn starch

Brown rice syrup

Corn sugar

Brown sugar


Cane sugar

Erythitol (if pure)

Carob powder


Corn syrup

Glucose polymers

Date sugar




Fruit juice sweeteners

Grape syrup



Maple syrup








The second type of fructose intolerance is dietary fructose intolerance (DFI), also called fructose mal-absorption. DFI is quite common—according to the U.S. National Library of Medicine's Genetics Home Reference center, fructose malabsorption may affect up to 40% of people in the Western hemisphere. Its exact incidence is also difficult to evaluate since many people show no symptoms at all and its cause is not precisely known. It seems to be caused by the lack of special cells (epithelial cells) on the surface of the intestine that usually aid in digestion. As a result, the body is not able to absorb fructose efficiently.


Fructose is a monosaccharide, or simple sugar, that has the same chemical formula as glucose, the main source of energy for the body, but a different molecular structure. It is found in all fruits, in some vegetables, and in honey. Fructose and other sugars are carbohydrates, which are important sources of energy for the body. The main types of sugars found in beverages and foods are lactose, maltose, dextrose, corn syrup, and high fructose corn syrup.

Sources of fructose

The HFI Laboratory at Boston University has prepared a list of sugars and their tolerance. Sweeteners that are not generally tolerated include:

Foods not allowed in a fructose and sucrose-free diet include:

Other foods that must be avoided include catsup, sauces that contain sugar, chile piquin with lemon, all regular soft drinks and sodas, jams, jellies, marmalades, maple syrup, canned or bottled fruits, and corn syrup.

Foods that are allowed on a fructose-free diet include:

Excessive acidity of body fluids due to accumulation of acids.
Any of a group of substances that includes sugars, starches, celluloses, and gums and serves as a major calorie source in food.
Corn syrup—
Sugar produced from corn starch that consists chiefly of single glucose molecules.
Another name for glucose, it is obtained from sugar cane, sugar beets, and starches.
The process by which food is chemically converted into nutrients that can be absorbed and used by the body.
Any of a class of sugars, including lactose and sucrose, that is composed of two monosaccharides.
A protein that changes the rate of chemical reactions within the body without being depleted.
Sugar found in fruits.
A monosaccharide sugar occurring widely in most plant and animal tissue. In humans, it is the main source of energy for the body.
The storage form of glucose found in the liver and muscles.
High fructose corn syrup (HFCS)—
A mixture of glucose and fructose sugars, also produced from corn starch.
A deficiency of sugar in the blood caused by too much insulin or too little glucose.
Disaccharide containing glucose and galactose (milk sugar). It occurs naturally in milk.
Poor absorption of nutrients.
Disaccharide containing two glucoses. It is obtained from starch.
Any of several carbohydrates, such as glucose, fructose, galactose, that cannot be broken down to simpler sugars.
A source of nourishment, especially a nourishing ingredient in a food.
Sugar alcohol food additive used as a sweetener in commercially prepared low sugar foods and gum.
A naturally abundant nutrient carbohydrate found in seeds, fruits, tubers, and roots.

Other permitted foods include coffee, tea, diet soft drinks that use artificial sweeteners, cocoa, salt, pepper, and other spices.

Fructose, sucrose, and sorbitol are used in many manufactured foods to such an extent that very few processed foods are allowed in the diet. Sugar is used in many other less obvious products such as canned food, bottled sauces, flavorings, and even prescription drugs—sucrose and sorbitol are also often used in medications as bulking agents or to improve the taste. Sorbitol is very often used as an artificial sweetener, especially in diabetic foods and drinks, which should accordingly be avoided. Isomalt and lycasin, alternative sweeteners that are predominantly used in confectionary sweets, also contain sorbitol. Glucose can be used as an alternative sweetener and as a source of energy.

Only vegetables that contain predominantly starch are allowed in the diet. New potatoes have a higher fructose content than old potatoes. Cooked vegetables have a lower fructose content and should be selected rather than raw vegetables, as the cooking process results in a loss of free sugars. Vegetables provide a good source of fiber that may be otherwise difficult to obtain. Fiber is usually found in fruits, vegetables, and whole grains. Wholemeal flour contains more fructose than white flour because both germ and bran contain sucrose, so whole-grain foods, such as brown rice and whole-grain pasta, contain more sucrose than the refined products.

Causes and symptoms

The symptoms of both types of fructose intolerance are gastrointestinal distress, flatulence, bloating, diarrhea, fatigue, vomiting, low iron, and other nutrient deficiencies. Dietary fructose intolerance has also been associated with mood disturbances and depression. The function of a fructose-free diet is to eliminate dietary sugar intake so as to alleviate these symptoms.


Clinical intolerance to fructose was initially described in 1956. Some 4–5 years later, the defect in aldolase B enzyme in the liver was demonstrated, and hereditary fructose intolerance (HFI) became clinically recognized. The rapid early progress in the understanding of this disorder may be due to the fairly clear symptoms associated with ingestion of fructose, which are difficult to miss. In many young infants, the age of onset of symptoms leads to the diagnosis. Genetic counseling may be of value to prospective parents with a family history of fructose intolerance. Other tests that may be run include a blood sugar test, kidney function tests, liver function tests, a uric acid blood test, and urinalysis.


Although they have different causes, both HFI and DFI are treated by dietary adjustments. Complete elimination of fructose and sucrose from the diet is the only effective treatment for HFI. DFI treatment also involves a fructose-free diet, with the treating physician allowing some concessions in mild cases. A strict fructose-free diet involves exclusion of any beverage or food containing fructose, sucrose, or sorbitol. Some patients may find a threshold level and can eat some fructose without getting symptoms. Close dietary monitoring is important for good outcomes and should include at least semiannual visits to a biochemical geneticist (for HFI) and monthly meetings with a registered dietitian.

Nutrition and dietary concerns

Eating out is one of the most challenging parts of maintaining a fructose-free diet. This is because restaurant employees have little time to check food contents on the labels of the ingredients used by the kitchen to prepare menus. Some suggestions for eating at restaurants include:


Sugar is often an ingredient in foods that the consumer is not aware of, and not only in restaurants. High fructose corn syrup (HFCS) is present in products such as soft drinks, fruit drinks, sports drinks, baked goods, candies, jams, yogurts, condiments, canned and packaged foods, and other prepared and sweetened foods. Also, potatoes may provide a significant amount of fructose if prepared in a certain way. For this reason, the guidance of a registered dietitian is required for the treatment of fructose intolerance.


Absolute elimination of fructose and glucose from the diet produces good outcomes in most people with fructose intolerance. Medical researchers unanimously agree that symptoms of dietary fructose intolerance can improve in patients willing to adhere to a low fructose diet. Research performed at the University of Innsbruck in Austria showed that fructose- and sorbitol-reduced diets in subjects with fructose malabsorption did not only reduce gastrointestinal symptoms but also improved mood and early signs of depression. Improvement of the signs of depression were more pronounced in females than in males. For a rapidly diagnosed and treated infant, the outcome for a normal state of health is excellent. In the absence of substantial liver damage, life expectancy is normal.


There is no known prevention for fructose intolerance.

See also CSIRO total wellbeing diet .



Cornblath, Marvin, and Robert Schwartz. Disorders of Carbohydrate Metabolism in Infancy. 3rd ed. Boston: Blackwell Scientific, 1991.

Gazzola, Alex. Living with Food Intolerance. Overcoming Common Problems. London, UK: Sheldon Press, 2006.

Smith, Judy. Living with Dietary Fructose Intolerance: A Guide to Managing Your Life with This New Diagnosis. Charleston, SC: BookSurge, 2006.


Gijsbers, C. F. M., C. M. F. Kneepkens, and H. A. Büller. “Lactose and Fructose Malabsorption in Children with Recurrent Abdominal Pain: Results of Double-Blinded Testing.” Acta Paediatrica 101, no. 9 (May 11, 2012): e411–15. (accessed April 5, 2018).

Latulippe, Marie E., and Suzanne M. Skoog. “Fructose Malabsorption and Intolerance: Effects of Fructose with and without Simultaneous Glucose Ingestion.” Critical Reviews in Food Science and Nutrition 51, no. 7 (August 2011): 583–92.


American Gastroenterological Association. “Food Allergies and Intolerances 101: Food Allergy vs. Food Intolerance.” (accessed April 5, 2018).

Genetics Home Reference. “Hereditary Fructose Intolerance.” Lister Hill National Center for Biomedical Communications, U.S. National Library of Medicine, National Institutes of Health. (accessed April 5, 2018).

HFI Laboratory at Boston University. “HFI Treatment.” (accessed April 5, 2018).

MedlinePlus. “Hereditary Fructose Intolerance.” U.S. National Library of Medicine, National Institutes of Health. (accessed April 5, 2018).


American Gastroenterological Association, 4930 Del Ray Ave., Bethesda, MD, 20814, (301) 654-2055, Fax: (301) 654-5920,, .

HFI Laboratory, Boston University, 24 Cummington St., Department of Biology, Boston, MA, 02215, .

Monique Laberge, PhD

  This information is not a tool for self-diagnosis or a substitute for professional care.