March 31, 2014

On March 5, 2014, the World Health Organization (WHO) Nutrition Guidance Expert Advisory Group (NUGAG) released its draft guidance on sugars intake. This draft guidance was developed to update WHO's 2003 guideline that "free sugars" not exceed 10% of total energy intake per day. The Canadian Sugar Institute, Nutrition Information Service has carefully reviewed the draft guideline document, as well as the two WHO-commissioned systematic reviews and their supplementary material published separately. Below is a brief scientific review of the draft guideline.

The WHO draft guideline recommends reducing free sugars intake throughout the lifetime and includes two specific targets in relation to dental caries. These include the previous 10% recommendation as a 'strong' recommendation, based on evidence graded as 'moderate' in relation to dental caries (not obesity). The WHO recommendation of further reduction to below 5% total energy, classified as 'conditional', was also based on evidence in relation to dental caries and graded as 'very low quality'. 

The draft guidance was based on two systematic reviews commissioned by the WHO to assess the effects of increasing or decreasing intake of "free sugars" on excess weight gain (Te Morenga et al., 20131) and dental caries (Moynihan et al., 20132). These reviews provide an important contribution to the scientific literature; however the draft guideline fails to reflect the weakness of the evidence in the two reviews and conflicting conclusions of other scientific authorities3,4 based on the review of the totality of scientific evidence. The guideline relates to "free sugars", however, the two WHO-commissioned reviews examined studies looking at "total sugars", "free sugars", as well as sugar-containing foods and beverages. The analysis of results was unable to distinguish any specific effects of "free sugars" from these studies, which undermines the interpretation and applicability of the study outcomes to specific guidance pertaining to "free sugars". 

  • Body weight: Te Morenga et al.1 reviewed randomized clinical trials and cohort studies on sugars and body weight. Among trials of adults with no strict control of food intake, only a small change (on average 0.8 kg) in body weight was observed when sugars were either increased or decreased in the diet. Evidence was less consistent in children than in adults. The changes in body weight were linked to changes in caloric intake (i.e., there was no unique effect of sugars as compared to other carbohydrates on body weight). The review did not provide any evidence to support a quantitative limitation for "free sugars". 
  • Dental caries: The Moynihan et al. review2 on dental health concluded there is "moderate quality" evidence from cohort studies (but not from randomized clinical trials) to support limiting intake of "free sugars" to less than 10% of energy. The conditional 5% recommendation was based on three "very low quality" ecological studies linking changes in sugar availability data for the entire country of Japan with dental caries incidence among children in two Japanese cities before and after World War II. This research predates the widespread use of fluoride toothpaste and did not account for other known confounders for dental caries including frequency of intake of sugars and other fermentable carbohydrates (e.g. dietary starch)3,4. These isolated studies do not reflect the current situation, particularly in developed countries such as Canada, and do not consider the internationally recognized use of fluoride as the primary prevention method. The effective use of fluoride continues to be the most effective public health approach to the prevention of dental caries in the 21st century5

Summary of WHO Scientific Support for WHO Draft Quantitative Recommendations
WHO draft recommendation Strength of Recommendation Strength of Evidence Type of Evidence WHO Reference
"In both adults and children, WHO recommends that intake of free sugars not exceed 10% of total energy" Strong recommendation1

moderate

dental caries, not obesity

5 observational studies in children; insufficient data for pooling. Annex 1, Table 5
"WHO suggests further reduction to below 5% of total energy" Conditional recommendation2

very low

dental caries, not obesity

3 ecological studies in Japanese children; correlation of dental caries with sugar supply before and in the years following WW II. Meta-analysis not possible due to the variability of outcome measures. Annex 1, Table 6

With strong recommendations, the guideline communicates the message that the desirable effects of adherence to the recommendation outweigh the undesirable effects. This means that, in most situations, the recommendation can be adopted as policy.

Conditional recommendations are made when there is greater uncertainty about the four factors (i.e. quality of evidence, balance of benefits versus harms and burdens, values and preferences, and resource use); or if local adaptation has to account for a greater variety in values and preferences; or when resource use makes the intervention suitable for some locations but not others. This means that there is a need for substantial debate and involvement of stakeholders before this recommendation can be adopted as policy.

  • In its "remarks", the WHO draft guideline states that "No harm is associated with reducing the intake of free sugars to less than 5% of total energy, particularly when considering the risk of dental caries throughout the life-course." This opinion is neither referenced nor supported by evidence in the two systematic reviews, and is inconsistent with the reviews of other authorities, including the Institute of Medicine (IOM)3 and European Food Safety Authority (EFSA)4. The IOM Dietary Reference Intake (DRI) report showed that when added sugars intakes are very high (>25% energy) or very low (<5% energy), micronutrient intakes can be compromised in some populations3. A more recent systematic review found that micronutrient intakes are optimal at moderate levels of sugars in the diet. Energy intake is the prime predictor of micronutrient adequacy and optimal intakes of sugars are difficult to quantify because associations vary between nutrients and depend on food choice and composition6.

The DRI forms the basis of dietary advice in Canada and the United States and found insufficient evidence to set an upper limit on added sugars in relation to dental caries, behavior, cancer, obesity, and hyperlipidemia. A maximum intake of 25% or less of energy from added sugars is suggested based on the decreased intake of some micronutrients in American subpopulations exceeding this level3.

Added sugars consumption in Canada has been declining and averages approximately 11% of total energy intake7.

WHO draft guideline announcement: WHO opens public consultation on draft sugars guideline

Canadian Sugar Institute, Nutrition Information Service: Submission to WHO, Flora Wang, PhD

 

References:

1. Te Morenga L, Mallard S, Mann J. Dietary sugars and body weight: Systematic review and meta-analyses of randomised controlled trials and cohort studies. British Medical Journal. 2013;346:e7492.

2. Moynihan PJ, Kelly SAM. Effect on caries of restricting sugars intake: Systematic review to inform WHO guidelines. Journal of Dental Research. 2013;93:8-18. 

3. Food and Nutrition Board, Institute of Medicine, National Academy of Sciences. Dietary reference intakes for energy, carbohydrates, fiber, fat, protein and amino acids. National Academic Press. Washington. 2005. 

4. European Food Safety Authority. Scientific opinion on dietary reference values for carbohydrates and dietary fibre. EFSA Panel on Dietetic Products, Nutrition and Allergies. EFSA Journal. 2010; 8(3):1462.

5. Jones S, Burt BA, Petersen PE, Lennon MA. The effective use of fluorides in public health. Bulletin of the World Health Organization. 2005. 83;670-676. 

6. Gibson SA. Dietary sugars intake and micronutrient adequacy: A systematic review of the evidence. Nutrition Research Reviews. 2007; 20:121-131. 

7. Canadian Sugar Institute. Further analysis of Statistics Canada Health Report: Sugar consumption among Canadians of all ages. 2011.