There’s no nutritional need or benefit that comes from consuming added sugar, yet our global supply of heavily processed foods is full of it—from breakfast cereals and salad dressings, to pasta sauces and soda. Sugary drinks are of particular concern, as they are a well-documented contributor to the obesity epidemic, and multiple studies link these beverages to increased risk of type 2 diabetes, as well as heart disease and other chronic conditions. As a result, dietary sugar has increasingly come under the health policy spotlight, with some key developments over the past year. To recap:
- The 2015-2020 Dietary Guidelines for Americans included a limit on added sugar to less than 10 percent of total daily calories (following evidence-based recommendations from the Dietary Guidelines Advisory Committee). This same limit was also previously recommended by the World Health Organization in 2015.
- The announced updates to the U.S. Nutrition Facts Panel, which will include a new line disclosing “added sugars.”
- The American Heart Association’s recommendation that children and teens consume less than 25 grams, or 6 teaspoons, of added sugar per day.
- The national and international policy discussions and actions focusing on sugar-sweetened beverages, from proposed and passed sugary drink taxes, to San Francisco’s warning label on outdoor soda advertising.
This week, in a review published by the Annals of Internal Medicine (AIM), these and other global guidelines to limit sugar consumption are being called into question, as the authors say the advice is “based on low-quality evidence.” The authors also conclude with the statement that, “there seems to be no reliable evidence indicating that any of the recommended daily caloric thresholds for sugar intake are strongly associated with negative health effects.”
This conclusion highlights a key flaw underlying the entire premise of this paper. In the development of any of these guidelines, there was never any belief that there is a specific “threshold” for harm due to sugar intake. As Dr. Walter Willett, chair of the Department of Nutrition at the Harvard Chan School explains, thresholds rarely exist in nutrition or biology, and goals or targets are often based on a continuum of risk:
“Behind these guidelines, the overall evidence supports a continuum of increasing risk with increasing intake of sugar or sugar-sweetened beverages. In translating this continuum of risk, a goal or target is often used to provide practical and clear guidance. Note that this is also true for blood cholesterol levels, blood pressure, blood glucose, and many other factors used in clinical practice or public health guidance. In setting targets or goals, issues of practicality as well the data are often considered, and there is almost always some element of arbitrariness when there is a continuum of risk and no threshold. Further, for these clinical measures the specific targets have evolved over time, even though there was no doubt that high levels of cholesterol, blood pressure, and glucose were associated with negative health outcomes.”
For dietary sugar, the evidence on adverse effects of higher intake has been accumulating over the last 20 years. The evidence of harm—which was not reviewed in this AIM study—is now strong, particularly for risk of diabetes and weight gain (this was documented extensively in the report of the 2015 Dietary Guidelines Advisory Committee). Further, as the study acknowledged, there is no evidence of benefit. It would be expected that the target levels would evolve with time, and even with the same data, different groups might suggest different targets, depending in part on circumstances specific to the location reached by each guideline. Willett adds that “The 10 percent goal in recent guidelines is very consistent with an increase in risk of type 2 diabetes, even with one serving of SSB’s per day as documented in prospective studies or the evidence of weight gain with this amount of sugar.”
Beyond methodology, it’s crucial to point out that the research was funded by the International Life Science Institute, a group with financial ties to many large food and beverage companies. This has been a key source of criticism from scientific experts in media coverage of the study (New York Times and NPR), and was addressed at length in an editorial published alongside the review, “Guidelines to Limit Added Sugar Intake: Junk Science or Junk Food?” by Dr. Dean Schillinger and Dr. Cristin Kearns:
“Industry documents show that the F&B [Food & Beverage] industry has manipulated research on sugars for public relations purposes…In summary, our concerns about the funding source and methods of the current review preclude us from accepting its conclusion that recommendations to limit added sugar consumption to less than 10% of calories are not trustworthy. Policymakers, when confronted with claims that sugar guidelines are based on ‘junk science,’ should consider whether ‘junk food’ was the source.”
In the editorial, Schillinger and Kearns also discredit additional flaws underlying the conclusion of “low-quality evidence” behind the various recommendations to limit added sugar, and note that “high quality journals could refrain from publishing studies on health effects of added sugars funded by entities with commercial interests in the outcome.”
Once again, our bodies do not require nor do they benefit from added sugar, and the link between sugar-sweetened beverages and obesity is supported by high-quality research. When the average American consumes 22 teaspoons of added sugar per day, (1) would it be responsible for guidelines to stay silent on added sugar in light of the available evidence? Moreover, what weight should this AIM study carry in policy discussions, when the authors even state that they have a “financial conflict of interest and readers should consider our results carefully”?
“This review is reminiscent of tactics often invoked by tobacco companies to deny scientific evidence of harm,” adds Dr. Frank Hu, professor of nutrition and epidemiology at the Harvard Chan School. “The main goal of these types of studies is to manufacture doubt and argue against taking actions. However, compelling evidence indicates harmful effects of regular consumption of added sugars—especially sugary beverages on health outcomes—and supports current recommendations to reduce consumption of added sugars.”
- Added Sugar in the Diet
- Sugary Drinks
- Soft Drinks and Disease
- Ask the expert: Sugary drinks and genetic risk for obesity
- Johnson RK, Appel LJ, Brands M, et al. Dietary sugars intake and cardiovascular health: a scientific statement from the American Heart Association. Circulation. 2009;120:1011-20.