Low to moderate consumption of beverages sweetened with fructose or glucose is associated with adverse changes in glucose and lipid metabolism and markers of inflammation, researchers from Switzerland report.
"The message for me and other physicians is that we really underestimated the adverse effects of soft drinks," Dr Kaspar Berneis from University Hospital Zurich, said. He added that he didn't expect to see such effects in young, healthy men.
Dr Berneis and colleagues investigated the effects of 5 different sugar-sweetened beverages (medium fructose, high fructose, medium glucose, high glucose, and high sucrose) in a crossover study of 29 healthy, normal-weight male volunteers between 20 and 50 years old.
Their results appear online June 15 in the American Journal of Clinical Nutrition.
Fasting glucose increased by 4% to 9% after the interventions (p<0.05), and waist-to-hip ratio was significantly higher than at baseline in all interventions containing fructose compared to baseline.
Percentage body fat was significantly higher in the high fructose intervention than in the high glucose intervention (15.7% vs. 15.1%; p<0.005), and waist circumference was significantly higher in the high sucrose intervention than in the high glucose intervention (82.9 cm vs. 82.6 cm; p<=0.005).
LDL particle size decreased by 0.51 nm after the high fructose intervention and by 0.43 nm after the high sucrose intervention. Medium and high fructose and high sucrose significantly decreased the large LDL I subclass. Total, LDL, and HDL cholesterol didn't change after any of the interventions.
High sensitivity C-reactive protein increased significantly after all interventions (by 60% to 109%), with the highest values resulting from high fructose consumption (430.1 ng/L; p<0.0017).
Leptin levels increased after medium and high glucose, but not after the other interventions, and liver function was unaffected by any of the interventions.
Conclusion based on the figures above
The results suggest "a more detrimental effect of fructose compared with glucose", the researchers note. "These differences may be due, at least in part, to the fact that although calorically identical to glucose intake, fructose metabolism differs considerably from that of glucose."
"It is the first study which shows a causal relationship (and not only an association) with the consumption of low or moderate dosages of these soft drinks, which provided only 6.5% of daily energy in the form of soft drinks," Dr Berneis said.
"Comparable studies have used fructose in amounts that provides 25 to 60% of total daily energy corresponding to sugars provided by 1.7 litres of soft drinks. So the point is that this is a very realistic study and we show these effects in young, healthy men, which we did not at all expect."
In response to questions about high-fructose corn syrup ads in the United States, Dr Berneis explained, "The points you raise about sucrose come from persons who do not know that half of sucrose consists of fructose.
Sucrose consists of one molecule of glucose and one molecule of fructose. The most adverse effects, indeed, we have seen in soft drinks containing fructose, which of course includes drinks containing sucrose."
(Reuters Health, Will Boggs MD, July 2011)