In hereditary fructose intolerance, the second step in the body's processing of fructose is impaired, causing the accumulation of toxic intermediates upon ingestion of fructose. This causes immediate symptoms such as nausea, vomiting, abdominal pain, sweating, confusion or fainting. In the long term, it can even lead to liver and kidney damage, and death. These symptoms occur in early life, when fruits and vegetables are introduced. Treatment consists of completely avoiding all foods containing fructose (and sorbitol). This allows patients with inborn fructose intolerance to lead relatively normal lives. An extensive list of safe products and which food products to avoid can be found here.
It is estimated that 1 in 35,000 people are affected by hereditary fructose intolerance. It is likely that some people have this disease without knowing it themselves. Indeed, some patients with hereditary fructose intolerance (and their parents) “learn” to avoid fructose-containing foods that cause symptoms, without seeing a doctor.
Dietary advice for HFI
Scientific research into hereditary fructose intolerance
Scientific research is conducted at the Department of Endocrinology and Metabolic Diseases to gain more insight in HFI. Under the direction of Professor Brouwers, we are investigating:
- Exactly how often hereditary fructose intolerance (HFI) occurs;
- What the quality of life and care needs of patients with HFI are;
- What are the long-term consequences of HFI;
- Whether alternative treatments than diet are possible.
There is intensive collaboration with the University of Boston and UZ Leuven.
Recent studies
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People with HFI must follow a strict diet throughout their lives. This could affect their quality of life. This was studied using two questionnaires and compared with patient with phenylketonuria (PKU) in het Netherlands and Belgium. PKU is another inborn error of metabolism in which patients must also follow a strict (protein-restricted) diet for life.
This study revealed that people with HFI rated their overall quality of life as good on average. Yet it was found that the fitness and mood of people with HFI is lower than that of people with PKU. The reason for this is not entirely clear. Possibly it has to do with their diet.
People with HFI also experience a greater social impact of their condition, which is mainly because they have difficulty in constantly having to explain about HFI and their diet. On the other hand, people with HFI experience less temptation and guilt when eating foods that are not allowed. This is probably due to the acute symptoms they experience after eating fructose.
The full paper can be found here.
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Currently, the only treatment for hereditary fructose intolerance is a fructose-restricted diet. In Maastricht, a team of researchers recently studied the possibility of treating HFI with medication. This new drug blocks the accumulation of toxins in HFI. The researchers treated people with hereditary fructose intolerance with the drug and then gave them a drink containing fructose. Where fructose normally provokes many symptoms in HFI, this time nothing happened. The participants seemed to tolerate the fructose very well.
Although these are promising findings, this does not mean that the drug can already be prescribed to patients with HFI. More research needs to be done. This will take some time, but the first step towards a new possible treatment has been taken.
The full paper can be found here.
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People with HFI often suffer from fatty liver, despite strictly following their fructose-free diet. The exact cause of this has been investigated in mice. These “HFI mice” also get sick after eating fructose and also have more fat in their liver.
It was found that a breakdown substance of fructose, which piles up in HFI, stimulates the uptake of glucose in the liver. The glucose is then converted to fat. This mechanism offers a possible explanation for why people with HFI are more likely to pile up fat in their liver. It is too early to translate these findings into a treatment for people with HFI. The full paper can be found here.
Another study on fatty liver in people with HFI used similar “HFI mice”. This study focused on the effect of mannose supplementation on the degree of fatty liver in these mice. In people with HFI the accumulation of fructose intermediates blocks another important enzyme, MPI. This blockage of MPI could lead to liver damage in people with HFI. Mannose, a natural sugar, would bypass this MPI blockade and reduce liver damage.
This study found that mannose supplementation did not improve fatty liver in the HFI mice. Thus, mannose supplementation does not appear to be an effective treatment for people with HFI.
The full paper can be found here.
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Currently, the only treatment for hereditary fructose intolerance is a fructose-restricted diet. However, research is also being conducted into the possibility of treating HFI with medication in the future. This study investigated whether patients with HFI would be open to a pharmacological treatment that could (partially) replace the diet.
Patients were presented with choice tasks to choose between their current diet and imaginary drugs that differed in, for example, side effects, cost and the effect on their current diet. Patients still chose their diet in most situations, but 86% chose pharmacological treatment in at least one choice task. Medication was especially preferred when it had no side effects, was free of costs and only had to be taken on social occasions (such as eating out) without dietary restrictions.
It was also found that younger patients and those who indicated that the disease or diet had a high impact on their lives were more likely to prefer medication.
These results show that there is interest in a pharmacological treatment for HFI, but only under certain conditions. Especially in social situations, or if the diet interferes with daily life, medication seems desirable. This will help researchers in the future to develop a treatment that fits well with what patients prefer.
The full paper can be found here.