Fructose may alter metabolism in ways scientists are still uncovering

Scientists are warning that fructose—a sugar found in sweetened foods and drinks worldwide—may damage health in ways not fully understood until now. A report published in Nature Metabolism reviewed evidence on sweeteners including table sugar and high-fructose corn syrup, both of which contain glucose and fructose.

Fructose behaves differently inside the body than glucose does, researchers say. "Fructose is not just another calorie," said Richard Johnson, MD, professor at the University of Colorado Anschutz and study lead author. "It acts as a metabolic signal that promotes fat production and storage in ways that differ fundamentally from glucose."

The body processes fructose through metabolic pathways that bypass normal regulatory controls, according to the report. This process can increase fat production, reduce cellular energy levels and generate compounds linked to metabolic dysfunction. Over time, these changes may raise the risk of metabolic syndrome—a group of conditions tied to obesity, insulin resistance and heart disease.

The body can also produce fructose internally from glucose, researchers note. This means fructose's role in disease may be broader and more complicated than previously thought. The findings arrive as obesity and diabetes rates climb worldwide, with free sugar intake remaining higher than recommended in many countries.

Fructose may once have helped humans survive food shortages by enabling efficient energy storage. In modern environments where calorie-rich foods are constantly available, however, the same biological mechanisms now appear to contribute to chronic disease. Johnson said: "Understanding its unique biological effects is critical for developing more effective strategies to prevent and treat metabolic disease."