Nutritional guidelines restricting sugar intake are not based on low to very-low quality evidence, finds a Canadian meta-analysis.
The study was led by McMaster University and The Hospital for Sick Children (SickKids).
The research team conducted a systematic review of nine public health guidelines on sugar recommendations, including those by the influential US Dietary Guidelines for Americans and the World Health Organisation (WHO) and found that the recommendations for limiting sugar are based on low to very low quality evidence.
"Although our findings question the recommendations from guidelines produced by leading authorities, the findings should not be used to justify high or increased consumption of nutrient-poor, energy-dense foods and beverages like candy and sugar-sweetened beverages," says Bradley Johnston, principal investigator of the review. "We know that it is healthy and advisable to limit our sugar intake, the question remains to what degree, and if we are limiting our sugar intake what are we replacing the sugar with?"
Official caps on sugars vary widely, from less than 5% of total daily calories, as recommended by the WHO, to advice from the Institute of Medicine which suggests the public to limit sugars to less than 25% of total daily calories.
"When respected organisations issue conflicting recommendations it can result in public confusion, and this raises concerns about the quality of the guidelines, and the quality of the evidence that informed the guidelines," says Johnston. He is an assistant professor in the department of clinical epidemiology and biostatistics at McMaster University; an assistant professor of health policy, management and evaluation at the University of Toronto; and scientist in child health evaluative sciences at SickKids.
Johnston uses former "low-fat" guidelines as an example: "For 40 years it was advised to eat a low fat diet and, as a result, the food industry and the public looked for ways to lower fat content in foods. What happened is that the fat was typically replaced by simple carbohydrates which included sugar creating a less than optimal outcome including an associated rise in obesity and diabetes.
"In the case of lowering sugar intake, what is happening is that sugars are often replaced with starches and other food additives like maltodextrine, providing the same calorie count, but often accompanied by an increased glycaemic index (and blood glucose levels)."
The research team identified problems with the nutritional guidelines and in particular problems with the research that supported the guidelines' recommendations such as; the inclusion of imprecise or small studies; a high risk of bias from uncontrolled studies; the use of outcome measures such as "nutrient displacement, tooth decay and limited weight gain" that are of lower priority to the public, compared to arguably more important outcomes such as obesity and diabetes; a lack of transparency regarding financial conflicts of interest among groups members who developed the guidelines, and a failure to include patient and public representatives in the panels drawing up the guidelines.
Co-first author, Behnam Sadeghirad, a McMaster PhD student in health research methodology, said "At present, there does not appear to be reliable evidence indicating that any of the recommended daily caloric thresholds for sugar intake are strongly associated with negative health effects. The results from this review should be used to promote improvement in the development of trustworthy guidelines on sugar intake."
Abstract
Background: The relationship between sugar and health is affected by energy balance, macronutrient substitutions, and diet and lifestyle patterns. Several authoritative organizations have issued public health guidelines addressing dietary sugars.
Purpose: To systematically review guidelines on sugar intake and assess consistency of recommendations, methodological quality of guidelines, and the quality of evidence supporting each recommendation.
Data Sources: MEDLINE, EMBASE, and Web of Science (1995 to September 2016); guideline registries; and gray literature (bibliographies, Google, and experts).
Study Selection: Guidelines addressing sugar intake that reported their methods of development and were published in English between 1995 and 2016.
Data Extraction: Three reviewers independently assessed guideline quality using the Appraisal of Guidelines for Research and Evaluation, 2nd edition (AGREE II), instrument. To assess evidence quality, articles supporting recommendations were independently reviewed and their quality was determined by using GRADE (Grading of Recommendations Assessment, Development and Evaluation) methods.
Data Synthesis: The search identified 9 guidelines that offered 12 recommendations. Each of the reviewed guidelines indicated a suggested decrease in the consumption of foods containing nonintrinsic sugars. The guidelines scored poorly on AGREE II criteria, specifically in rigor of development, applicability, and editorial independence. Seven recommendations provided nonquantitative guidance; 5 recommended less than 25% to less than 5% of total calories from nonintrinsic sugars. The recommendations were based on various health concerns, including nutrient displacement, dental caries, and weight gain. Quality of evidence supporting recommendations was low to very low.
Limitation: The authors conducted the study independent of the funding source, which is primarily supported by the food and agriculture industry.
Conclusion: Guidelines on dietary sugar do not meet criteria for trustworthy recommendations and are based on low-quality evidence. Public health officials (when promulgating these recommendations) and their public audience (when considering dietary behavior) should be aware of these limitations.
Authors
Jennifer Erickson, Behnam Sadeghirad, Lyubov Lytvyn, Joanne Slavin, Bradley C Johnston
[link url="https://www.sciencedaily.com/releases/2016/12/161219200951.htm"]McMaster University material[/link]
[link url="http://annals.org/aim/article/2593601/scientific-basis-guideline-recommendations-sugar-intake-systematic-review"]Annals of Internal Medicine abstract[/link]