People with hereditary fructose intolerance have an inherited condition which prevents them from digesting a sugar called fructose. Ingesting fructose when the body cannot digest it can cause dangerous side effects which may eventually lead to jaundice and liver disease. For this reason, people with this disorder must follow a special hereditary fructose intolerance diet which eliminates all sources of this sugar.
Fructose is a type of sugar which is present in honey and fruits, and is also a component of sucrose, or table sugar. Fructose is often added as a sweetener to processed foods and drinks, including many baby foods. The prevalence of fructose in both natural and processed foods makes avoiding this substance a complicated business.
Hereditary fructose intolerance is a genetic congenital disorder, meaning that someone with this disorder is born with it as a result of an inheritable genetic mutation. People with fructose intolerance are deficient in a liver enzyme called aldolase-B, which is crucial for the metabolism of fructose. Eating fructose in the absence of this enzyme causes metabolic problems that can, in turn, cause dangerously low blood sugar, as well as kidney and liver toxicity. This is because aldolase-B deficiency also prevents efficient use of phosphates, which are needed to convert stored glycogen into glucose. The end result is not only hypoglycemia, but also dangerously high levels of toxic metabolites in the liver.
Children with this disorder will begin to display symptoms soon after they are first fed sucrose or fructose-containing formulas or other foods. In children, hereditary fructose intolerance symptoms may include poor feeding, digestive problems after eating fructose or sucrose, excessive sleepiness, irritability, vomiting, jaundice, and seizures, convulsions. Possible complications include uncontrolled bleeding, liver enlargement, liver disease, and eventually liver failure. Some people are also at risk of developing gout, as this condition can also increase blood levels of uric acid.
Complete elimination of all dietary fructose is the only treatment for hereditary fructose intolerance, and there is no cure for the disorder. A fructose-free diet requires eliminating fruit and fruit products, honey of all kinds, sucrose, and all foods which contain either fructose or sucrose as a sweetening agent. This includes syrups such as maple syrup, molasses, corn syrup, and agave syrup, all of which contain either fructose or sucrose. Processed foods containing any of these sweeteners must also be avoided. Prognosis for people with this disorder is good as long as the diet is followed scrupulously.
