In 2005, the average American consumed 64 killigrams of added sugar, a sizeable proportion of which came through drinking soft drinks. Now, in a 10-week study, Peter Havel and colleagues, at the University of California at Davis, Davis, have provided evidence that human consumption of fructose-sweetened but not glucose-sweetened beverages can adversely affect both sensitivity to the hormone insulin and how the body handles fats, creating medical conditions that increase susceptibility to heart attack and stroke.

In the study, overweight and obese individuals consumed glucose- or fructose-sweetened beverages that provided 25 percent of their energy requirements for 10 weeks. During this period, individuals in both groups put on about the same amount of weight, but only those consuming fructose-sweetened beverages exhibited an increase in intra-abdominal fat. Further, only these individuals became less sensitive to the hormone insulin (which controls glucose levels in the blood) and showed signs of dyslipidemia (increased levels of fat-soluble molecules known as lipids in the blood). As discussed in an accompanying commentary by Susanna Hofmann and Matthias Tschöp, although these are signs of the metabolic syndrome, which increases an individual’s risk of heart attack, the long-term affects of fructose over-consumption on susceptibility to heart attack remain unknown.