Feeding a sweet tooth won't just lead to weight gain and a mouthful of cavities. A new study suggests that diets high in added sugars can alter levels of important blood fats and increase the risk of cardiovascular disease.
The study, published in the Wednesday edition of the Journal of the American Medical Assn., found that people who got at least 25% of their daily calories from added sugars of any kind were 3.1 times more likely to have low levels of so-called good cholesterol in their bloodstream than people who got less than 5% of their calories from added sweeteners.
Additionally, those who consumed more than 17.5% of their calories from the sugars — be it ordinary table sugar derived from sugar cane or sugar beets, high fructose corn syrup or any other caloric sweetener — were 20% to 30% more likely to have high levels of blood fats called triglycerides than people with the low-sugar diets, the study found.
The association between sugar intake and blood lipids was independent of the harmful effects of other components of sugary processed foods, such as fat and cholesterol. The link also persisted when researchers took into account smoking and drinking habits and levels of physical activity.
"There is a specific added-sugar effect," said Dr. Miriam Vos, a pediatric gastroenterologist at Emory University in Atlanta who led the study.
The findings support guidelines released last year by the American Heart Assn. recommending that men eat no more than 150 calories of added sugars each day and that women limit themselves to 100 calories. That works out to about 5% of daily intake.
That's far less than the 25% limit suggested in 2005 by the Institute of Medicine, which advises the government on health matters. The World Health Organization endorses a limit of 10%, an amount that didn't appear to harm blood lipid levels in the new analysis.
To reach their conclusions, Vos and her colleagues at Emory and the Centers for Disease Control and Prevention examined data from 6,113 American adults who participated in the CDC's National Health and Nutrition Examination Survey between 1999 and 2006. Survey workers took measurements of height, weight and blood pressure, drew blood samples and asked participants detailed questions about everything they ate in a 24-hour period.
Then the researchers calculated the amount of added sugars — defined as all caloric sweeteners used to enhance prepared and processed foods — and total calories in all of those meals and snacks. They determined that Americans eat an average of 21.4 teaspoons of added sugars each day, which translates to 359 calories and 16% of the average daily total. In the late 1970s, added sugars accounted for 11% of total calories.
Only 15% of people in the study got less than 5% of their daily calories from added sugars.
The researchers found that the more sugary a person's diet, the lower their blood levels of high-density lipoprotein, or HDL, the good cholesterol that is believed to transport dangerous cholesterol away from the arteries. Also, as the proportion of calories from added sugars rose past 10%, so did the level of triglycerides, which is fat that circulates in the blood. Low HDL cholesterol and high triglycerides both increase the risk for heart disease.
Scientists who weren't involved with the study said they weren't surprised that added sugars were linked to levels of cholesterol and fat in the blood. Small studies have shown that when people consume large amounts of either added sugars or pure fructose, which makes up 50% of table sugar and 55% of high fructose corn syrup, their bodies respond by making more triglycerides and less HDL cholesterol.
The new study confirms that sugar has the same effect when consumed as part of a typical American diet, said Judith Wylie-Rosett, who heads the Division for Behavioral and Nutritional Research at Albert Einstein College of Medicine in New York.
"It means it applies to all of us," she said.