Sugar Guidelines Have Flimsy Evidence, Reports New Study
A review of various dietary sugar guidelines has found that recommendations on how much sugar one should consume in a day vary widely and are based on low to very low quality evidence.
Sugar limits are spelled out in many public health guidelines, including those issued by the U.S. Dietary Guidelines for Americans and the World Health Organization. While some guidelines suggest capping your sugar intake at less than five percent of total daily calories, others suggest less than 25 percent is good. (How much is that in English? If we meet somewhat midway and say 10%, that's 200 calories from sugar on a typical 2,000 calorie a day diet—or 50 grams, or 12 teaspoons.) Still other guidelines don't quantify the limit. The study is published Dec. 19 in the Annals of Internal Medicine.
The researchers found nine guidelines offering 12 recommendations, says study leader Bradley Johnston, PhD, assistant professor of clinical epidemiology and biostatistics, McMaster University. He is also assistant professor of health policy, management and evaluation at the University of Toronto and a scientist at the Hospital for Sick Children. Seven studies did not offer a quantitative number, and the other five gave recommendations that varied from the 5 to 25% ranges.
Dealing with the Disparities
So how much sugar is too much? When considering how much sugar is too much, "you can ask the questions in different ways," says Joanne Slavin, PhD, RD, a coauthor and professor of food science and nutrition at the University of Minnesota, St. Paul. Some, for instance, look at when added sugar becomes a problem for a specific outcome, such as low calcium. Others try to link added sugars to specific health outcomes and decide how much is too much.
The experts who developed the various guidelines looked at different evidence, says Dr. Johnston.
And they had different ways of evaluating the overall evidence, he says. "We think that the guideline groups generally did a poor job of interpreting the evidence," he says. Some groups may have had panelists with industry sponsorship, and that could have made them more lenient in setting sugar guidelines, Dr. Johnston says.
The evidence may have been weighed differently. Some guidelines may have put a higher value on limiting sugars to avoid weight gain short term, he says; others may have looked at how best to limit sugar to avoid dental cavities.
The guidelines don't adhere to established standards, Dr. Johnston says, such as the 2011 Institute of Medicine guidelines for trustworthiness, and other accepted measures.
It's worth pointing out that some experts lashed out at the study, citing bias due to industry sponsorship. The study was funded by the International Life Sciences Institute, an industry non-profit member group. The study authors wrote the study protocol and conducted the study indpenedently of the institute.
Take-Home for Consumers?
No one's saying to ignore the guidelines. What's needed, the researchers say, is standardization of guidelines and acceptance of definition of basic terms. "It might be helpful to first agree on definitions of carbohydrates," Dr. Slavin says. "In Europe they talk about free sugars, and that would include the sugars in fruit juice. In the U.S., sugars in fruit juice are not added sugars. Without a standard definition of what is an added sugar, it is difficult to move very far in an evidence-based review."
While researchers sort all that out over time, what's good advice for the rest of us?
Connie Diekman, RD, M Ed, director of university nutrition at Washington University in St. Louis, commented on the study and its implications. "The diversity of dietary recommendations for added sugar might seem confusing, but the important message from all of them is that added sugars tend to be low in nutritional value—they provide flavor and calories—and therefore they need to be incorporated as appropriate for the individual," she says.
"Added sugars can fit into a healthful eating plan if that eating plan does two things," she says. "One, it includes foods that provide more nutritional like whole grains, fruits, vegetables and healthful protein choices and second, if an individual’s calorie needs allow for the added sugar calories.''
Diekman adds: "Trying to blame single foods or nutrients for our “weight woes” isn’t going to change behavior and misses the important point – a healthful eating plan is about good nutrient balance, appropriate portions and enjoyable options – otherwise it becomes a quick-fix diet."
She also suggests avoiding a common pitfall-reducing your sugar intake and then replacing sugars with worse options. "So don't cut out dessert but add salty snacks," she says.