Co-written with Melinda Dalla-Zuanna.
People with hereditary fructose intolerance (HFI), experience a range of unpleasant symptoms when they eat fructose.
Symptoms of fructose intolerance include nausea, vomiting, bloating and abdominal discomfort, but HFI individuals can appear symptom-free unless they ingest fructose. Symptoms generally disappear rapidly, usually within days after removing fructose from the diet1.
Sorbitol and sucrose must also be avoided if a person has HFI because fructose can be synthesised from sorbitol and sucrose (table sugar)2.
Fruit naturally contains fructose, but there are lots of other foods that you might not be aware of that also contain fructose, or sorbitol and sucrose, as added sweeteners. These other foods include desserts, cakes, chocolate, lollies, soft drinks and sports drinks.
Fructose has been painted as a bit of bad guy in the media, so to make sure you’re getting the right information pop over to Nutrition Australia and read this article too.
HFI usually appears in infants during weaning as baby formulas and/ or solid food containing fructose are introduced to the infant and the infant ceases to receive lactose as a source of carbohydrates from breastmilk. As a result, children develop an aversion towards sweet foods to protect themselves from developing symptoms3.
Continued consumption of fructose, sorbitol or sucrose can result in several chronic effects such as fructosemia (increased plasma fructose concentrations), hypophosphatemia (abnormally low levels of phosphate in the blood), hepatic (liver) and renal (kidney) failure, hyperuricemia (excess uric acid in the blood), hypoglycaemia abnormally low level of glucose in the blood) and hypermagnesemia (abnormally elevated levels of magnesium in the blood)2.
HFI is caused by mutations in an enzyme linked to the break down dietary fructose called aldolase-B4. A loss of function in this enzyme disrupts the metabolism of FBP (fructose-1,6-bisphosphate) and F1P (fructose-1-phosphate)5 which basically means that the pathways in our bodies that are responsible for storing and creating energy get a bit messed up.
If aldolase-B activity is reduced, we get a build-up of F1P which in turn inhibits fructokinase6, and we get less inorganic phosphate2 and it’s from this issue that most pathological problems arise.
So how is HFI diagnosed?
Rather obviously, fructose intolerance is suspected when a person displays known symptoms which disappear on a fructose-free diet4. It is also diagnosed by assaying patient tissue samples or by trying to produce symptoms with an IV dose of fructose. The most common testing, and cheapest and least invasive, is with genetic screening.
There is currently no cure available2 but HFI is easily managed through the lifelong exclusion of fructose, sorbitol and sucrose from the diet1.
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- Steinmann, B., Santer, R., & van den Berghe, G. (2006). Disorders of fructose metabolism. In: Fernandes J, Saudubray JM (eds) Inborn metabolic diseases: diagnosis and treatment (5th ed, pp 135–142). New York: Springer.
- Bouteldja, N., & Timson, D. J. (2010). The biochemical basis of hereditary fructose intolerance. Journal of Inherited Metabolic Disease, 33(2), 105-12. doi: 10.1007/s10545-010-9053-2
- Yasawy, M. I., Folsch, U. R., Schmidt, W. E., & Schwend, M. (2009). Adult hereditary fructose intolerance. World Journal Of Gastroenterology, 15(19), 2412-2413. doi: 10.3748/wjg.15.2412
- Wong, D. (2005). IEM digest: Hereditary fructose intolerance. Molecular Genetics and Metabolism, 85(3), 165-167. doi: 10.1016/j.ymgme.2005.05.001
- Malay, A., D., Allen., K., N., & Tolan, D., R. (2005). Structure of the thermolabile mutant aldolase A149P: Molecular basis of hereditary fructose intolerance. Journal of Molecular Biology, 347, 135-144. doi: 10.1016/jmb2005.01.008
- Ali, M., Rellos, P., & Cox, T., M. (1998). Hereditary fructose intolerance. Journal of Medical Genetics, 35, 353-365. doi: 10.1136/jmg.35.5.353