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What is Hereditary Fructose Intolerance?

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  • Written By: Emma Lloyd
  • Edited By: Bronwyn Harris
  • Last Modified Date: 30 March 2018
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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.

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anon311641
Post 4

I have fructose intolerance. But nature took good care of me. I have protection. It seems I don't have the right receptors on my tongue for sweet food (anything - it could be even some vegetables). My body rejects it even before swallowing, so there are no complications as described in the article. I am lucky.

serenesurface
Post 3

@simrin-- You're right. Fructose malabsorption is less serious than fructose intolerance. It doesn't lead to kidney and liver failure as HFI does. But both are treated in the same way. Patients of both disorders have to eliminate fructose from their diets.

About your other question on breast milk, I'm really not sure. Although I know from a distant relative whose son has malabsorption that she also had to eliminate fructose from her diet while she breastfed him. So I think that breast milk is safer for the child, but the mom might have to follow a strict diet too.

SteamLouis
Post 2

Thanks for this article, it's very informative. I would like to know more about two points which I don't think I understood.

Firstly, why doesn't fructose intolerance happen even when breastfeeding? Doesn't the fructose that the mom eats get transferred over to the baby during feeding?

My other question is about the difference between HFI and fructose malabsorption. I have heard this term as well and thought initially that it was the same thing. Is it a less serious version of fructose intolerance?

Thanks!

candyquilt
Post 1

Fructose intolerance is not very common. I read that one in twenty thousand people have it. I think that's why we are not very informed about the disorder. And there are little or no alternatives to fructose containing products in grocery stores.

So people with fructose intolerance have to take on the responsibility of selecting foods carefully, reading each and every label before buying. It must be very difficult and challenging to do. I try to avoid foods with high fructose corn syrup and I know how hard that is itself.

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