Just as recent science has divided dietary fats into good, bad and really bad categories, some scientists now think different sugars also may deserve individual scrutiny.
Most experts agree that Americans eat too much sugar, period. But studies in recent years suggest that a simple sugar called fructose might contribute in unique ways to pre-diabetic conditions, obesity and cardiovascular disease.
Fructose, which makes up about half of table sugar and standard high-fructose corn syrup, is metabolized solely by the liver. The other major simple sugar, glucose, can be used by all organs. Researchers are finding that bombarding the liver with high levels of fructose can produce excess internal fat and elevate levels of uric acid, effects that can contribute to insulin resistance, diabetes and heart disease. Some animal studies also link fructose to reduced sensitivity to leptin, a hormone that signals the body to stop eating.
Not all researchers are convinced that fructose poses a unique threat. But the surge in the U.S. of Type 2 diabetes, fatty liver disease, kidney stones and other weight-related ailments has led the National Institutes of Health to convene a conference in November that will explore the role of fructose consumption in liver function, obesity and diabetes.
"I think that generally speaking we are moving toward a consensus that fructose is the component of sugar that matters," said Barry Popkin, a professor of global nutrition at the University of North Carolina who has looked closely at sugar and obesity. "The conference may help explain a lot of mechanistic issues related to fructose and a whole series of cardiometabolic diseases."
In addition to fueling scientific discussion, the new studies have added a wrinkle to the debate pitting high-fructose corn syrup against table sugar. While the U.S. Food and Drug Administration in 1983 declared the sweetener to be safe at levels of up to 55 percent fructose (slightly higher than table sugar's 50 percent), it has not taken a position on high-fructose corn syrup formulations that contain more.
According to a 2010 study published in the journal Obesity, some of America's most popular soft drinks (Coke, Pepsi and Sprite) can be formulated with corn sweeteners that are nearly 65 percent fructose.
Fructose is intensely sweet and cheaper than other sugars, so boosting levels in a product could reduce calories and costs while keeping the desired sweetness, said lead author Michael Goran, a professor of preventive medicine and director of the Childhood Obesity Research Center at the University of Southern California.
Beverage industry lobbyists have challenged his findings, saying Goran should have used more sensitive testing methods. Goran said follow-up analyses using those methods on a broader array of food and drinks confirmed the original results.
One maker of high-fructose corn syrup, Decatur-based Archer Daniels Midland, has been marketing a product called Cornsweet 90, with 90 percent fructose, for several years. The company recommends it for "reduced calorie beverages, jellies and dressings."
The FDA said in 1996 that it could not determine the safety of HFCS-90 because it has a "substantially different ratio of glucose to fructose" and ADM provided no safety data on the product. That does not make it illegal, the FDA says, because the submission of safety information on new ingredients is voluntary under federal rules.
The FDA says it doesn't know how much HFCS-90 or other "fructose dominant" sweeteners may be in the food supply, and neither the American Beverage Association nor the Corn Refiners Association responded to Tribune questions about where and how those sweeteners are used. ADM referred questions to the Corn Refiners Association.
Last month the advocacy group Citizens For Health sent a petition to the FDA asking that the agency require disclosure of fructose levels in food, much in the same way that labels must list trans fats. The group describes itself as "passionately committed to unfettered citizen-consumer access to natural health choices" but acknowledges receiving funding from the sugar industry and other business groups. The Corn Refiners Association has called the petition a "scare tactic" and "the latest unfounded attack on high-fructose corn syrup" by a group with questionable motives.
Some researchers studying the possible adverse effects of fructose support labeling, saying it's a concern that people consuming high-fructose corn syrup don't know how much fructose they are ingesting.
"HFCS may contain variable amounts, which is one of the reasons fructose levels should be on the label," said Kimber Stanhope, a nutritional biologist in the molecular biosciences department at the University of California at Davis who studies fructose and metabolism.
Pediatric endocrinologist Robert Lustig of the University of California at San Francisco said he has equal disdain for table sugar and for standard high-fructose corn syrup at 55 percent fructose, but "higher percentages of fructose would be more damaging" to the body, he said.
Lustig said he thinks labeling would be useful but should be accompanied by public education about fructose.
"Much of the public still thinks that a calorie is a calorie, sugar is sugar and all sugars are the same," he said. "They don't even understand that sugar is anything more than empty calories."
Dr. John Bantle, a professor of medicine in the division of endocrinology and diabetes at the University of Minnesota Medical School, will co-chair a panel at the National Institutes of Health conference but is not convinced that fructose is less healthful than other sugars.
"There's so much concern, and people wonder if fructose is driving these negative health effects and the obesity epidemic," Bantle said. "I think the answer is probably 'yes,' but so is pizza and other cheap food that tastes good."
Bantle said he thinks using higher fructose blends to reduce the number of calories in pancake syrup and other products can be beneficial in moderation.
But Jim Turner, one of the Citizens For Health lawyers who filed the FDA petition, thinks such products are dangerous when consumers don't know how much fructose they contain.
Without labeling, "people who are trying to take care of their health or help their kids could end up with higher fructose consumption levels that may have fewer calories but could end up damaging their liver," he said.
One of the most vocal critics of the recent anti-fructose wave is John Sievenpiper, a nutritional sciences researcher at the University of Toronto. His meta-analyses of short-term studies on the effects of different sugars and carbohydrates on body weight, blood pressure and uric acid found no unique harm from fructose when calories remained the same.
When fructose is added to a controlled diet — something like adding a big sweet drink to one's regular meal — "there is a strong and reproducible effect on body weight" and other negative outcomes, he said. But Sievenpiper attributes that to the added calories.
Numerous public health campaigns have aimed to reduce public consumption of sugary beverages, but Sievenpiper said he believes a focus on soft drinks misses the point.
"Going after this one ingredient has distracted us from the major issue, which is overconsumption," said Sievenpiper, who acknowledges accepting several grants from Coca-Cola Co. and least one from Archer Daniels Midland. "We eat too much of everything, including fructose. The fact is we are eating too much in general."
Stanhope said she disagrees with the Sievenpiper's assessment that all sugars cause the same metabolic reactions. She conducted studies in which one group of older overweight men and women added fructose-sweetened drinks to their diet and another added glucose-sweetened drinks. The research found "very different metabolic effects of fructose compared to glucose," she said, including an increase in visceral fat around internal organs and a decrease in insulin sensitivity.
The U.S. Department of Agriculture puts no specific cap on sugar servings in its dietary guidelines, but the American Heart Association recommends no more than 100 calories of added sugar a day for women (6 teaspoons) and 150 calories for men.
A single 12-ounce can of soda may contain 130 calories' worth of sugar, already exceeding the daily limit for a woman. USDA figures from 2006 found that the average white male teenager took in a daily 392 calories from sugar-sweetened beverages, roughly the number contained in a large (32-ounce) McDonald's Coke. Based on the fructose levels Goran found in bottled Coke, that drink alone could deliver about 67 grams of fructose.
While the debate about fructose continues, most researchers studying the issue say there's no reason not to cut down on sweets and sweet drinks.
"What are the risks associated with reducing the amount of sugar you consume just in case these studies are absolutely dead-on right?" Stanhope said. "The biggest risk is that you might consume fewer calories and eat more fruits and vegetables and cut down on cookies, cakes, candies and soda. In other words, there's no risk at all."