Fructose Linked to More Metabolic Problems than Glucose

Overweight or obese patients who consumed soft drinks sweetened with either glucose or fructose both gained weight.

Peter J. Havel, M.D., of the University of California, Davis, reported that only those who had the fructose drinks saw an increase in visceral adipose tissue, dyslipidemia, hepatic de novo lipogenesis, and insulin resistance.

In the real world, most people consume a combination of the two simple sugars, either as sucrose (table sugar) or high-fructose corn syrup, used in many sweetened beverages and commercial products.

Dr. Havel's group noted that, previous research had established that fructose is associated with a variety of adverse effects in animals, but evidence was lacking in humans.

So they enrolled 32 patients in a double-blinded, parallel arm study. For 10 weeks, the patients consumed 25% of their daily energy from soft drinks sweetened with either fructose or glucose.

Both groups gained comparable amounts of weight, but those who drank fructose-sweetened drinks had an increase in lipid deposition in visceral adipose tissue. Those who drank glucose-sweetened beverages had an increase in subcutaneous adipose tissue.

They also found that fructose consumption increased plasma concentrations of fasting small dense LDL and oxidized LDL, whereas glucose consumption did not.

The researchers said these changes "may be associated with an increased risk of cardiovascular disease."

Hepatic de novo lipogenesis was also increased in those who had fructose drinks, but not those who had glucose drinks. Subsequently, the researchers said, increased lipids from fructose-induced de novo lipogenesis led to insulin resistance as well.

The researchers noted that average consumers drink beverages sweetened with either sucrose (50% glucose, 50% fructose) or high-fructose corn syrup (55% glucose, 45% fructose), rather than either of the pure sugars.

So, it may be that the adverse effects of these sweeteners are "diluted" by their lower fructose content relative to pure fructose, the researchers said.

Also, the average American consumes about 16% of daily energy from added sugars, not the exaggerated 25% in the study.

The researchers said that further studies are needed to determine what levels of dietary added sugars "are associated with adverse changes of lipids and decreased insulin sensitivity in different populations."

Susanna M. Hofmann, M.D., and Matthias H. Tschop, M.D., of the University of Cincinnati said in an accompanying editorial, "The findings make clear that chronic overconsumption of dietary sugars in general is detrimental to our health, and these effects may be synergistic with chronic increases in caloric intake."

"The findings provide major scientific progress by demonstrating marked differences in the metabolic effects of these two major sugars with respect to their ability to promote intra-abdominal lipid deposition and hepatic lipid production, while shifting cholesterol metabolism in an unfavorable manner and diminishing insulin sensitivity in humans."

Practice Pearl:

Explain that patients who consumed drinks sweetened with fructose had an increase in visceral adipose tissue, dyslipidemia, de novo lipogenesis, and insulin resistance, compared with those who drank glucose- sweetened drinks.

Stanhope KL, et al "Consuming fructose-sweetened, not glucose-sweetened, beverages increases visceral adiposity and lipids and decreases insulin sensitivity in overweight/obese humans" J Clin Investigation2009; DOI: 10.1172/JCI137385.