It's common knowledge that sugar is no friend to your waistline, but research is starting to uncover exactly how bad it is for the rest of your body. According to a study published in the Archives of Internal Medicine, the simple carbohydrates found in sugary treats like doughnuts and ice cream may increase your risk of coronary heart disease. That could be, as another study in the Journal of the American Medical Association found, that the added sugars in processed foods may increase your cholesterol.
The JAMA study authors analyzed seven years of data from the National Health and Nutrition Examination Survey, administered annually by the Centers for Disease Control and Prevention. The data tracks such things as diet, body mass index, cholesterol level, and blood pressure, as well as behaviors like smoking, exercise, and alcohol consumption. After excluding people with diabetes, those who were excessively overweight, and those with high cholesterol, the researchers found that adults consumed an average of 21.4 teaspoons of added sugar a day, that is, sugar that doesn't exist naturally in foods such as milk or fruit. That amount equaled 16 percent of their total caloric intake, and for about 16 percent of the sample, sugar comprised more than 25 percent of total calories. (Current recommended daily guidelines are 5 teaspoons for women, 9 teaspoons for men, and 5 percent or less of daily calories.)
Even more alarmingly, the study showed that as the number of added-sugar calories increased, the levels of good cholesterol (HDL) went down, and bad cholesterol (LDL) and triglycerides (another blood fat) went up. These strong associations held true even after the researchers controlled for other risk factors for high cholesterol and heart disease.
How and why added sugars increase cholesterol level isn't fully understood, say the authors, but one theory is they cause your liver to secrete more bad LDL cholesterol and interfere with the body's ability get rid of it. "Taking a broader view, we know that a diet high in added sugars is a marker for a poor-quality diet in general," says Rachel K. Johnson, PhD, MPH, RD, associate provost and professor of nutrition at the University of Vermont in Burlington. Johnson authored the American Heart Association's (AHA's) recommendations for sugar intake because, she says, there's already a large body of evidence suggesting that added sugar is bad for the heart.