Fructose and glucose have the same caloric value, but the two sugars are metabolized differently.
It emerges that mice that cannot metabolize fructose are healthier when placed on carbohydrate rich diets.
New research results published in Nature (Lyssiotis & Cantley) - here are a few pearls from the study:
- “A drastic increase in dietary sugar consumption in the western world during the past four decades has been paralleled by epidemics of obesity and metabolic syndrome, suggesting a cause-and-effect relationship. Yet the relative contribution of individual sugars — as opposed to total caloric intake — to this epidemic remains controversial. For instance, increased intake of fructose, which is enriched in soft drinks and processed foods, has been proposed to greatly contribute to these disorders.”
- “From an energetic standpoint, a molecule of glucose has the same caloric value as a molecule of fructose. However, the human body treats these carbohydrates quite differently, raising questions about their individual roles in obesity and metabolic syndrome.”
- “In general, glucose is used directly by tissues such as the muscles and brain as an energy source. Excess glucose is stored in the liver as glycogen (a glucose polymer) but can also be converted into fructose by the polyol biochemical pathway (Fig. below). By contrast, fructose is almost exclusively metabolized by the liver. In this organ, ketohexokinase (KHK) — a liver-specific fructose-metabolizing enzyme also known as fructokinase — traps fructose in liver cells as fructose 1-phosphate. Unlike fructose-phosphate (an isomer of fructose 1-phosphate that participates in the biochemical pathway of glycolysis), fructose 1-phosphate can bypass a major regulatory step in glycolysis that generates fructose-bisphosphate through the action of the energy-sensitive enzyme phosphofructokinase. Thus, fructose can be converted into fat, unfettered by the cellular controls that prevent unrestrained lipid synthesis from glucose.”
- “…there are epidemiological links between fructose consumption, obesity and metabolic syndrome.”