On March 5th 2014, the World Health Organization (WHO) published draft guidelines on the consumption of free sugars by adults and children. The guidelines are open for consultation until the end of March. The guidelines aim to provide recommendations on the consumption of free sugars to reduce the risk of noncommunicable diseases, focusing on the prevention and control of weight gain (as obesity is a risk factor for several noncommunicable diseases) and dental caries (tooth decay).
Free sugars are defined as ‘mono- and disaccharides added to foods by the manufacturer, cook or consumer, and sugars naturally present in honey, syrups, fruit juices and fruit concentrates’ and the current guidance is that free sugars contribute no more than 10% total energy intake (WHO/FAO 2003). Due to recent debate regarding the intake of free sugars and adverse health effects, WHO reviewed the existing evidence and summarised its findings in this document. The guideline was put together following WHO developed procedures (WHO, 2012) and the evidence was reviewed using GRADE methodology (Grading of Recommendations Assessment, Development and Evaluation) by an expert panel (The WHO Nutrition Guidance Expert Advisory Group Subgroup on Diet and Health).
In order to develop the guidelines, two systematic reviews were commissioned to evaluate the effects of free sugars on excess weight gain (Te Morenga et al. 2013) and dental caries (Moynihan & Kelly 2014). The reviews assessed the effect of decreasing and increasing free sugars intake in both adults and children and the likely effect of restricting intake to below 10% total energy.
The review focusing on free sugars and excess weight gain included 30 randomised controlled trials (RCTs) and 38 cohort studies (Te Morenga et al. 2013). The review included RCTs that had investigated the effect of free sugars intake in isocaloric diets (when the calories are the same) on weight gain, and interventions involving advice to increase or decrease the consumption of free sugars without a focus on weight loss. The overall quality of the evidence for changes in body weight in adults as a result of modifying sugars intake was considered to be ‘moderate’ by the investigators and panel. Meta-analyses of categories of studies on adults (detailed in the guidelines) suggested an association between reduced dietary sugars intake and reduced body weight, a weight increase with increased dietary sugars intake and no change in body weight in isocaloric studies independent of sugars intake. With regards to children, the evidence that lower sugars was associated with lower body weights was considered ‘moderate’ quality, while that for higher sugars intakes and higher body weights was ‘low’ quality. A meta-analysis of five prospective cohort studies found that high sugar-sweetened beverage intakes were associated with higher body weight in children. It was concluded that the increase in body weight was most likely the result of excess energy intake.
The review investigating the relationship between free sugars intakes and dental caries looked at the effects in both adults and children (Moynihan & Kelly 2014). With regards to adults, two non-randomised intervention trials and three observational studies were included, all of which suggested an association between free sugars intakes and dental caries. For children, more studies that met the inclusion criteria were identified: 50 observational studies and one non-randomised intervention study. The majority of these studies (42/50) also suggested a positive association between free sugars and dental caries. The researchers then focused on five child cohort studies that considered fluoride exposure and allowed a comparison between the effects of free sugars intake of less than and more than 10% total energy. All of the studies reported more dental caries when free sugars intake was greater than 10% total energy. Additionally three studies, conducted on children in Japan, were identified to allow the comparison of dental caries with sugars intakes less than 5% total energy intake and more than 10% energy intakes. The data suggested a strong dose response relationship between sugars intake and dental caries. The investigators concluded that evidence of ‘moderate quality’ suggests that free sugars intake of less than 10% total energy reduces the risk of dental caries and that there is some suggestive evidence that the risk of dental caries would be lower with free sugars intake of less than 5% total energy intake.
As a result of this research, WHO has made two strong and one conditional recommendations*. For a strong recommendation to be made, the desirable effects of the recommendation outweigh the undesirable effect. However, conditional recommendations should be considered with more caution. These are made when there is greater uncertainty and further discussion is required before they can be adopted as policy. The recommendations were as follows:
• WHO recommends reduced intake of free sugars throughout the life-course (strong)
• In both adults and children, WHO recommends that intake of free sugars not exceed 10% of total energy (strong)
• WHO suggests further reduction to below 5% of total energy (conditional)
The guidelines state that the 5% recommendation is based on observational data that suggests there is a linear relationship between sugars intake and dental caries and that dental caries are progressive so a reduction in risk of caries in childhood is significant later in life. Additionally, it is noted in the report that reducing free sugars to less than 5% total energy intake would not be harmful.
The draft guidelines are out for public consultation and are under peer review simultaneously. Comments can be submitted via the WHO web site until March 31st (http://www.who.int/mediacentre/news/notes/2014/consultation-sugar-guideline/en/). At the end of this period, the comments will be reviewed and necessary revisions will be made. The guidelines will then be finalised and reviewed once again in 2019.
The main recommendation relating to the intake of free sugars not exceeding 10% total energy, classified as a ‘strong’ recommendation, was based on evidence in relation to dental caries regarded as ‘moderate’. This recommendation is the same as the existing recommendation and in effect the same as the UK recommendation of 10% total energy, or 11% food energy. The WHO recommendation of a further reduction to below 5% total energy is classified as a ‘conditional’ recommendation, and was based on evidence in relation to dental caries (not obesity prevention) regarded as 'very low quality'. This distinction was not picked up in the media coverage that followed publication of these recommendations.
*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.
Moynihan P.J., Kelly S.A (2014). Effect on caries of restricting sugars intake: Systematic review to inform WHO guidelines. Journal of Dental Research, 2014, (1):8-18 Available at: http://www.ncbi.nlm.nih.gov/pubmed/24323509 Accessed 6.3.14
Te Morenga L., Mallard S., Mann J (2013) Dietary sugars and body weight: Systematic review and meta-analyses of randomised controlled trials and cohort studies. British Medical Journal, 346:e7492
Available at: http://www.bmj.com/content/346/bmj.e7492.pdf%2Bhtml Accessed 6/3/14
WHO (World Health Organization) /FAO (Food and Agriculture Organization of the United Nations)(2003) 2002 WHO/FAO Expert Consultation on Diet, Nutrition and the Prevention of Chronic Diseases http://www.fao.org/docrep/005/AC911E/ac911e00.htm
WHO (World Health Organization) (2014) Draft Guidelines on free sugars released for public consultation Available at: http://www.who.int/nutrition/sugars_public_consultation/en/
WHO (World Health Organization) (2012) WHO handbook for guideline development. Geneva, World Health Organization Available at: http://apps.who.int/iris/bitstream/10665/75146/1/9789241548441_eng.pdf Accessed 6/3/14