Mice on a diet high in fructose suffered much worse metabolic effects than those given similar calories of glucose (the other component in table sugar) according to new research by the Joslin Diabetes Centre in the US.
The scientists went on to pinpoint the biological processes that help to explain the different results, which have been published in the Journal of Clinical Investigation.
The researchers experimented used mice to study obesity, type 2 diabetes, fatty liver and other metabolic illnesses. The animals were given either regular or high-fat diets, and drank either plain water or water sweetened with fructose or glucose.
Over 10 weeks, none of the animals on a regular diet developed insulin resistance (a key factor in metabolic disease), although those consuming either form of sugar gained substantially more weight.
Among animals on a high-fat diet, however, significant differences emerged between those drinking fructose and glucose.
Mice on the high-fat diet become much more obese and more insulin-resistant compared to those on the glucose diet. And while both groups of animals added fat to their livers, the fat composition was quite different.
The researchers also discovered that production of an enzyme called Khk (ketohexokinase), required for the first step of fructose metabolism, was increased in the livers of mice who drank fructose. When the scientists examined liver samples from obese human teenagers with fatty liver disease, they also found higher levels of this enzyme, which is specifically important in fructose, but not glucose, metabolism.
Samir Softic, the study’s first author, said: ‘Fructose was associated with worse metabolic outcomes. Kids also eat more sugar than adults, so fructose may be even more of a risk factor in children, which would add to their years of poor health.’