From the Research
Reducing sugars can be detected in the urine in hereditary fructose intolerance due to the impaired metabolism of fructose, which leads to secondary renal tubular dysfunction, as supported by the most recent study 1. This genetic disorder is caused by a deficiency of the enzyme aldolase B, which is necessary for fructose metabolism in the liver, kidneys, and small intestine. When fructose is consumed, it accumulates in these tissues, causing depletion of phosphate and ATP, which disrupts normal cellular function. The key points to consider are:
- The metabolic disruption affects the proximal renal tubules, impairing their ability to reabsorb various substances, including glucose and other reducing sugars.
- The resulting generalized proximal tubular dysfunction (Fanconi syndrome) allows glucose and other reducing sugars to pass into the urine rather than being reabsorbed into the bloodstream.
- This tubular dysfunction is reversible if fructose is removed from the diet, as noted in a study on the epidemiological aspects of hereditary fructose intolerance 2.
- Importantly, the glucosuria (glucose in urine) occurs despite normal blood glucose levels, distinguishing it from diabetic glucosuria.
- Patients with hereditary fructose intolerance typically need to follow a strict fructose-free diet to prevent these metabolic complications and other symptoms such as vomiting, hypoglycemia, and liver damage, as recommended in a comprehensive review of the disorder 1.