Hereditary Fructose Intolerance
Hereditary Fructose Intolerance (HFI) is an autosomal recessive inherited disease (both parents are carriers but have no symptoms) that prevents the body from metabolizing fructose due to the lack of a key protein needed for the process. In severe cases, HFI can result in the death of undiagnosed individuals. Infants with this disease are usually diagnosed with failure to thrive and aren't diagnosed with this disease at all. If the disease manifests in infancy, the mortality rate is high. Amazingly, many older individuals with HFI are not diagnosed, but learn to dislike foods that are dangerous to them. Indeed, our own experience with the disease has shown us that few physicians know much about this disease because it is rare (about 1 in 50-200,000). This disease is often confused with the more common Fructose Intolerance (also called Fructose Malabsorbtion). The latter disease is associated with digestive symptoms such as bloating and diarrhea and does not have the potential to have life threatening consequences.
Although the two diseases, HFI and FI differ in severity, the treatment for both is the same. The sufferer should avoid ingesting fructose. As we will discuss later, this is easier said than done. Most FI sufferers tolerate small amounts of fructose, since the failure to absorb the sugar takes place in the gut. The symptoms of FI are caused by the presence of this unabsorbed sugar which feed bacteria whose byproducts in turn cause the discomfort. With HFI, the fructose is absorbed through the gut into the blood stream but cannot be utilized by the body, and accumulates as a waste product that rapidly overwhelms the body’s ability to eliminate it. A large dose of fructose can cause kidney and liver failure and even death in an HFI subject.
Heriditary Fructose Intolerance (also called Fructosemia) has the same relationship to Fructose Intolerance as Galactosemia has to Lactose Intolerance (LI). Galactosemia is a serious genetic disorder that produes very similar symptoms to HFI when milk sugars are ingested, while simple Lactose Intolerance, produces bloating and diarrhea like FI. While very unpleasant, neither FI nor LI typically have very serious long term health implications.
Since the solution to both FI and HFI is to avoid fructose, it might seem that this solution is simple. Although the solution is simple, the implementation of a fructose-free diet is far from easy. Avoiding all fruits does not even begin to address the diet. Fructose is contained in large categories of foods for which alternatives are not easily obtained. Consider that wheat, corn, peas, carrots, tomatoes, beans, and the vast majority of processed and snack foods contain fructose. Also consider that fructose is not always evident on food labels. Common table sugar (sucrose) is a compound sugar that is half fructose, so no foods with any added sucrose are acceptable. Other sugars are also be polysaccharides (compound molecule sugars) and must be avoided.
To make matters much worse for the HFI sufferer, high fructose corn syrup (a cheap sweetener derived from corn syrup) seems to have taken over the food industry. This sweetener can be present in almost any food. It is contained in almost all prepared or processed foods (including pickles, meat products, salad dressings, etc.). We have also made the mistake of believing a label that claimed a product was “sugar free” that actually contained a prohibited non-sucrose sugar in addition to an acceptable artificial sweetener. Honey is almost pure fructose.
The symptoms of HFI include nausea, fatigue, weakness, headaches, abdominal and muscle pain, and tremors associated with low blood sugar (which is a paradoxical effect actually caused by the accumulated fructose interfering with the body’s metabolism). The onset of these symptoms can be anywhere from a few minutes to an hour after ingesting a fructose containing food and can persist for several days while the body struggles to eliminate the accumulated waste from the body.
While this blog is intended primarily to address a lack of information about HFI, the dietary guidance also applies to FI sufferers (although the need to completely eliminate all fructose is not absolute for these individuals).
Hereditary Fructose Intolerance (HFI) is an autosomal recessive inherited disease (both parents are carriers but have no symptoms) that prevents the body from metabolizing fructose due to the lack of a key protein needed for the process. In severe cases, HFI can result in the death of undiagnosed individuals. Infants with this disease are usually diagnosed with failure to thrive and aren't diagnosed with this disease at all. If the disease manifests in infancy, the mortality rate is high. Amazingly, many older individuals with HFI are not diagnosed, but learn to dislike foods that are dangerous to them. Indeed, our own experience with the disease has shown us that few physicians know much about this disease because it is rare (about 1 in 50-200,000). This disease is often confused with the more common Fructose Intolerance (also called Fructose Malabsorbtion). The latter disease is associated with digestive symptoms such as bloating and diarrhea and does not have the potential to have life threatening consequences.
Although the two diseases, HFI and FI differ in severity, the treatment for both is the same. The sufferer should avoid ingesting fructose. As we will discuss later, this is easier said than done. Most FI sufferers tolerate small amounts of fructose, since the failure to absorb the sugar takes place in the gut. The symptoms of FI are caused by the presence of this unabsorbed sugar which feed bacteria whose byproducts in turn cause the discomfort. With HFI, the fructose is absorbed through the gut into the blood stream but cannot be utilized by the body, and accumulates as a waste product that rapidly overwhelms the body’s ability to eliminate it. A large dose of fructose can cause kidney and liver failure and even death in an HFI subject.
Heriditary Fructose Intolerance (also called Fructosemia) has the same relationship to Fructose Intolerance as Galactosemia has to Lactose Intolerance (LI). Galactosemia is a serious genetic disorder that produes very similar symptoms to HFI when milk sugars are ingested, while simple Lactose Intolerance, produces bloating and diarrhea like FI. While very unpleasant, neither FI nor LI typically have very serious long term health implications.
Since the solution to both FI and HFI is to avoid fructose, it might seem that this solution is simple. Although the solution is simple, the implementation of a fructose-free diet is far from easy. Avoiding all fruits does not even begin to address the diet. Fructose is contained in large categories of foods for which alternatives are not easily obtained. Consider that wheat, corn, peas, carrots, tomatoes, beans, and the vast majority of processed and snack foods contain fructose. Also consider that fructose is not always evident on food labels. Common table sugar (sucrose) is a compound sugar that is half fructose, so no foods with any added sucrose are acceptable. Other sugars are also be polysaccharides (compound molecule sugars) and must be avoided.
To make matters much worse for the HFI sufferer, high fructose corn syrup (a cheap sweetener derived from corn syrup) seems to have taken over the food industry. This sweetener can be present in almost any food. It is contained in almost all prepared or processed foods (including pickles, meat products, salad dressings, etc.). We have also made the mistake of believing a label that claimed a product was “sugar free” that actually contained a prohibited non-sucrose sugar in addition to an acceptable artificial sweetener. Honey is almost pure fructose.
The symptoms of HFI include nausea, fatigue, weakness, headaches, abdominal and muscle pain, and tremors associated with low blood sugar (which is a paradoxical effect actually caused by the accumulated fructose interfering with the body’s metabolism). The onset of these symptoms can be anywhere from a few minutes to an hour after ingesting a fructose containing food and can persist for several days while the body struggles to eliminate the accumulated waste from the body.
While this blog is intended primarily to address a lack of information about HFI, the dietary guidance also applies to FI sufferers (although the need to completely eliminate all fructose is not absolute for these individuals).
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