Published Online: October 01, 2013
Mary K. Caffrey
Consuming too much sugar makes us gain weight, and being overweight is associated with poor cardiovascular health. But while multiple epidemiological studies have found an association between sugar intake and cardiometabolic disease, tagging sugar as the cause is another matter, according to Kimber Stanhope, PhD, RD, a nutritional biologist at the University of California-Davis.
Moving sugar, or at least some forms of it, from being linked to heart disease to being an actual cause is no small matter, Stanhope explained. Such a change, she said, requires “direct experimental evidence.”
Her group and others have studied sugar intensely in recent years, as the epidemics of obesity and diabetes have soared in the United States.1 Stanhope’s presentation at the 73rd Scientific Sessions of the American Diabetes Association in Chicago (June 21-25), “Does Sugar Consumption Contribute the Epidemics of Metabolic Disease?”,2 offered a review of her own ground-breaking work3 and that of others, notably the 2012 Maersk study,4 which found increases in liver fat among overweight patients who consumed drinks containing sucrose, compared with those drinking lowfat milk, water, or drinks with aspartame.
In 2012, news media—including Sanjay Gupta, MD, on 60 Minutes—began to attach the label “toxin”5 to sugar, based on Stanhope’s 2011 article in the Journal of Clinical Endocrinology & Metabolism, which found adverse cardiometabolic effects on healthy, young patients after only 2 weeks corn syrup.3 She shared additional unpublished data from this ongoing study, which so far confirm the initial findings. (Earlier studies by Stanhope’s team had involved older patients who were already overweight.)
Stanhope’s studies are highly involved. Participants must live at the research center for all or part of the time; while inpatient, they consume only those foods served by the study team. Every calorie is recorded, and frequent tests measure triglycerides, blood pressure, cholesterol, and uric acid, both after meals and after fasting. As she explained, the requirements of achieving the “gold standard” in nutritional research is one reason why moving from associating sugar with heart disease to showing a causal link is so difficult.
Much of Stanhope’s presentation focused on her findings on the differences between fructose and glucose, which has been the subject of critical papers published in 2009 and 2011.3,6 Stanhope took her audience on a tour through how each sugar travels through the liver, showing the key differences between how glucose and fructose are processed—and why the processed fructose in modern beverages stays put in the liver while glucose does not. This is true, she said, even when weight gain among test groups is the same.
As her presentation highlighted, Stanhope’s current study design of young adults does not occur in a vacuum. She noted the large discrepancy between the 2009 recommendation by the American Heart Association (AHA), which called for women to limit their added sugar to 100 kilocalories (kcal) per day, with men limiting theirs to 150 kcal/day, and that of the August 2010 Dietary Guidelines for Americans.
The official effort undertaken every 5 years by the US departments of Agriculture and Health and Human Services, the Dietary Guidelines issued conflicting advice. As Stanhope noted, the Dietary Guidelines called for no more than 25% of energy to come from added sugar. Stanhope illustrated the gap with a slide of soda cans, which looked suspiciously like Coca-Cola. For men, the difference was between 4 1/3 cans for the Dietary Guidelines recommendation and a single can for the AHA’s. “Clearly, in 2010 there was controversy in the role of sugar in the epidemics of metabolic disease,” she said.
What about today? The question remains unsettled, Stanhope said, but the abundance of epidemiological evidence, combined with very recent direct experimental evidence, suggests that sugar could be a cause of heart disease. The real question, Stanhope said, is whether it makes sense to wait for sugar to be deemed the culprit conclusively before we act. “Do we need to wait for
these results before we revise the Dietary Guidelines for Americans and start educating the public accordingly?” she asked.
Her comments were timely. Just a week earlier, the new advisory panel that will shape the 2015 Dietary Guidelines for Americans had held its first meeting in Bethesda, Maryland.7 The group is scheduled to take testimony October 3-4.