Fresh Take on Fructose vs. Glucose

Study Shows More Insulin Resistance With Fructose-Sweetened Beverages

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April 21, 2009 -- New research shows big differences in how the sugars fructose and glucose are metabolized by the body. But the findings have little relevance to the current debate about whether high-fructose corn syrup is a bigger dietary villain than other sugars added to processed foods, experts say.

Overweight study participants showed more evidence of insulin resistance and other risk factors for heart disease and diabetes when 25% of their calories came from fructose-sweetened beverages compared to glucose-sweetened beverages.

Both groups gained weight during the 10-week study, but the fructose group gained more of the dangerous belly fat that has been linked to a higher risk for heart attack and stroke.

The study showed clear differences in how fructose and glucose are metabolized by the body, nutrition researcher and principal investigator Peter J. Havel, PhD, of the University of California at Davis tells WebMD.

But the findings do not show that high-fructose corn syrup (HFCS), used in everything from soft drinks to cereals in the U.S., is worse for your health than other added sugars.

That's because despite the name, high-fructose corn syrup is chemically similar to other widely used sweeteners, including table sugar (sucrose), honey, and even sweeteners made from concentrated fruit juices.

All contain glucose and fructose in roughly equal amounts. The high-fructose corn syrup used in most soft drinks and other sweetened beverages in the U.S. contains about 55% fructose and 45% glucose, compared to the 50/50 fructose-glucose ratio found in table sugar.

"Any added sugar used as an alternative to high-fructose corn syrup would have a similar chemical composition," University of Cincinnati obesity researcher Matthias H. Tschop, MD, tells WebMD. "While it is possible that there are differences in how these sugars affect metabolic pathways, I know of no studies that show this."

But Tschop says the newly reported study is an important step forward in understanding the metabolic impact of glucose and fructose, even if the real-world public health implications are less clear.

Fructose and Glucose Study

The study included 32 overweight or obese men and women whose average age was 50.

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Over a 10-week period, the men and women drank either glucose- or fructose-sweetened beverages, totaling 25% of their daily calorie intake, either in an outpatient setting (eight weeks long) or highly controlled inpatient setting (two weeks long).

Both the groups gained weight during the trial, but imaging studies revealed that most of the added fat in the fructose group occurred in the belly, while most of the fat gained by the glucose group was subcutaneous (under the skin).

Belly fat, but not subcutaneous fat, has been linked to an increased risk for heart disease and diabetes.

The fructose group had higher total cholesterol and LDL "bad" cholesterol, plus greater insulin resistance, which are consistent with metabolic syndrome, while the glucose group did not.

The research appears in the latest issue of the Journal of Clinical Investigation.

Study on High-Fructose Corn Syrup Is Under Way

Havel acknowledges that the study does little to answer the question of whether the body processes high-fructose corn syrup differently from table sugar or other sweeteners.

His research team is in the early stages of a study that will address the issue. The investigation will compare the metabolic effects of fructose, glucose, table sugar, and high-fructose corn syrup in normal-weight and obese men and women.

Cardiologist James Rippe, MD, who is a consultant for the Corn Refiners Association, says there is no credible scientific evidence that high-fructose corn syrup is a bigger cause of obesity or chronic disease than any of the other sugars used in processed foods.

He points out that while high-fructose corn syrup is used almost exclusively to sweeten soft drinks in the U.S., this is not true in many other parts of the world.

Rippe is a professor of biomedical sciences at the University of Central Florida.

"Obesity and diabetes are on the rise in places where they don't use high-fructose corn syrup, such as Mexico, Europe, and Australia, just like in the United States," he says.

Tschop says whether the sweetener is high-fructose corn syrup or something else, it is clear that Americans are eating too much sugar.

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"The largest sources for daily overconsumption of sugar are soft drinks and other sweetened beverages," he says.

A non-diet 12-ounce soft drink typically contains nine or 10 teaspoons of sugar, which is close to the daily limit set for sugar consumption by many health organizations.

"Some people drink a 2-liter (67-ounce) bottle of soda a day or even more," he says. "If you do that for many years there is no doubt that it will impact your health, no matter what type of sugar is used."

But Rippe says targeting one type of sugar or even one food as the main culprit in the rise in obesity and obesity-related disease misses the point.

"We are eating too much of everything, not just sugar," he says. "Over the last three decades, the average American has increased their calorie consumption by 24% and physical activity has declined. People are singling out sugar as the one smoking gun in the obesity epidemic when there are guns everywhere."

WebMD Health News Reviewed by Louise Chang, MD on April 21, 2009

Sources

SOURCES:

Stanhope, K.L. Journal of Clinical Investigation, April 20, 2009, online edition.

Peter J. Havel, PhD, nutrition department, University of California, Davis.

Matthias H. Tschop, MD, associate professor, University of Cincinnati Obesity Research Center. 

James Rippe, MD, professor of biomedical sciences, University of Central Florida, Orlando; consultant, Corn Refiners Association.

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