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People eating the most added sugar also recorded the highest triglyceride levels, which are a type of fat formed when the body breaks down sugars for energy.
Low HDL and high triglyceride levels are two of the primary risk factors for heart disease. Exactly how dietary sugar contributes to these changes in blood lipid levels isn't clear yet, but researchers think it has something to do with fructose, a backbone of many sugars (particularly the high fructose corn syrup that is becoming ubiquitous in processed foods and sugared sodas). Fructose can prompt the liver to generate more cholesterol and metabolize triglycerides from sugar in the diet, as well as slow down the clearance of fats from the blood.
Dr. Rachel Johnson, a professor of nutrition at the University of Vermont, says she was encouraged by the results. Johnson was a member of the American Heart Association committee who advised Americans to limit added sugar to 5% of daily caloric intake. But at the time of the recommendation, she concedes, the data on the link between sugar and heart-hazardous lipid profiles was not as strong as the association between sugar and obesity and weight gain. "This paper adds strength to the evidence around added sugar and elevated triglycerides and lowered HDL," she says. "It's certainly an important paper."
But translating its results into public health benefits will take some doing, mainly because most Americans are unaware of how much added sugar they eat. Current nutrition labels on food do not distinguish between added sugar and naturally occurring sugar, lumping them together as carbohydrates. So it's nearly impossible for consumers to understand exactly how much added sugar they are taking in unless they are truly meticulous label readers. It's possible, says Johnson to extrapolate how much added sugar is in sweetened yogurt, for example, by comparing its label to that of an unsweetened version. And products such as raisin bran cereals may appear to contain a high amount of added sugar, when in fact much of it is actually naturally occurring sugar found in the raisins. "It is difficult for the consumer to know exactly how much added sugar he is getting," says Johnson.
The AHA and several other organizations, however, are petitioning the Food and Drug Administration to include added sugars on the label, just as trans fats are now separated from fats so consumer can become more fat smart about what they eat.
Until then, Johnson suggests a simple rule of thumb if the product doesn't contain ingredients that are naturally sweet, such as fruit, then most of the sugar content is likely added sugar. And added sugar, as Vos and her team found, can do far more harm than simply increase your pants size.