How is fructose digested?
Fructose is absorbed in the small intestine using a special transporter, the capabilities of which are limited. If more fructose is taken in than it can tolerate, the excess goes further into the colon. There, bacteria ferment it with the formation of gases and short acids, and fructose itself attracts water. Hence the bloating, rumbling, spasms and loosening of the stool. Interestingly, glucose helps the absorption of fructose, so regular sugar, where these molecules are in equal parts, is better tolerated than honey or apple juice with excess fructose.
- Limited fructose transporter capacity
- Excess goes into the colon
- Fermentation by bacteria and formation of gases
- Osmotic attraction of water
- Glucose improves fructose absorption
- Dose-dependent nature of symptoms
Two forms: how they differ
Fructose malabsorption is a common functional disorder and symptoms are limited to the intestines and depend on the amount ingested. Hereditary fructose intolerance is a rare disease with a deficiency of the enzyme aldolase B. When fructose enters the body, such children's glucose levels drop sharply, the liver and kidneys suffer, vomiting, lethargy, convulsions, and liver enlargement occur. It manifests itself with the introduction of complementary foods and juices. Children instinctively refuse sweets and fruits. This condition requires the immediate complete elimination of fructose, sucrose and sorbitol.
- Malabsorption - common, symptoms only intestinal
- Hereditary form - rare, with damage to the liver and kidneys
- Hereditary manifests itself with the introduction of complementary foods
- Characteristic aversion to sweets in children
- Different severity of restrictions
- The hereditary form is confirmed genetically
Symptoms of malabsorption
Complaints occur 30 minutes to several hours after eating foods rich in fructose. Typical symptoms include bloating, loud rumbling, spasms around the navel, excess gas, loose or pasty stools, and sometimes, on the contrary, constipation. Nausea and a feeling of fullness may occur. Symptoms are dose-dependent: a small portion of fruit is tolerated normally, a large glass of juice or a few apples causes a reaction. Often such patients also have poor tolerance to other fermentable carbohydrates.
- Bloating and rumbling in the stomach
- Spasms and pain around the navel
- Increased gas formation
- Loose stools or, less commonly, constipation
- Nausea and fullness
- Symptoms depend on the amount eaten
Survey
The main method for malabsorption is a hydrogen breath test with a fructose load: the hydrogen content in exhaled air is measured after taking a solution. A practical alternative is to trial eliminating high-fructose foods for 2–4 weeks and then gradually reintroduce them. Be sure to exclude other causes: celiac disease, lactose intolerance, giardiasis, inflammatory bowel disease. If a hereditary form is suspected, the child’s liver parameters, glucose, and liver condition are assessed by ultrasound and a genetic study is performed.
- Hydrogen breath test with fructose
- Trial Elimination Diet
- Coprogram and stool tests
- Tests for celiac disease and giardiasis
- Liver parameters and blood glucose
- Genetic research if a hereditary form is suspected
Food
If you have malabsorption, completely abstaining from fruits is unnecessary and harmful. The goal is to reduce the single dose and choose better-tolerated products. Limit honey, fruit juices, dried fruits, grapes, apples, pears, watermelon, as well as foods with added fructose and corn syrup. Berries, citrus fruits, kiwi, banana, melon are better tolerated in moderation, especially with other foods. Sorbitol and other -ol sweeteners increase symptoms. After a few weeks, the diet is gradually expanded, finding its threshold. In the case of a hereditary form, the exclusion is strict and lifelong, under the supervision of a doctor.
- Reduce your serving of fruit
- Limit honey, juices, dried fruits, grapes and apples
- Avoid products with corn syrup
- Eliminate sorbitol, xylitol and sugar-free chewing gum
- Eating fruit with other foods
- Gradually expand the diet, finding a tolerable dose