Tuesday, August 3, 2010

Fructose and the Paleo Model

"Research published by Peter Havel, a professor of nutrition at the University of California-Davis, suggests that compared with glucose, fructose incites less of an insulin response, which ultimately results in lower circulating levels of the appetite-suppressing hormone leptin and higher levels of the appetite-boosting hormone ghrelin-so fructose may make you hungrier.
"It could also put you at greater risk of heart disease and diabetes. When overweight people supplemented their diets with drinks sweetened either with fructose or with glucose for 10 weeks, fructose drinkers ended up with higher concentrations of small LDL particles in their blood after they ate. They also experienced, on average, a 20 percent drop in insulin sensitivity-low insulin sensitivity is a risk factor for type 2 diabetes-over the course of the experiment compared with the glucose drinkers."

Our laboratory has investigated 2 hypotheses regarding the effects of fructose consumption: 1) the endocrine effects of fructose consumption favor a positive energy balance, and 2) fructose consumption promotes the development of an atherogenic lipid profile. In previous short- and long-term studies, we showed that consumption of fructose-sweetened beverages with 3 meals results in lower 24-h plasma concentrations of glucose, insulin, and leptin in humans than does consumption of glucose-sweetened beverages. We have also tested whether prolonged consumption of high-fructose diets leads to increased caloric intake or decreased energy expenditure, thereby contributing to weight gain and obesity. Results from a study conducted in rhesus monkeys produced equivocal results. Carefully controlled and adequately powered long-term studies are needed to address these hypotheses. In both short- and long-term studies, we showed that consumption of fructose-sweetened beverages substantially increases postprandial triacylglycerol concentrations compared with glucose-sweetened beverages. In the long-term studies, apolipoprotein B concentrations were also increased in subjects consuming fructose, but not in those consuming glucose. Data from a short-term study comparing consumption of beverages sweetened with fructose, glucose, high-fructose corn syrup, and sucrose suggest that high-fructose corn syrup and sucrose increase postprandial triacylglycerol to an extent comparable with that induced by 100% fructose alone. Increased consumption of fructose-sweetened beverages along with increased prevalence of obesity, metabolic syndrome, and type 2 diabetes underscore the importance of investigating the metabolic consequences of fructose consumption in carefully controlled experiments.

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