Draft Guideline: Sugars intake for adults and children
Public consultation form
Response from the British Nutrition Foundation. 31st March 2014
We welcome the opportunity to respond to this consultation, our comments on the relevant sections of the draft guideline are outlined below.
We share WHO’s concerns about the impact of non-communicable diseases on health worldwide, both in developed and developing countries. The WHO report focusses on obesity and dental caries. With more than 1 billion people obese worldwide1 and the concomitant increased risk of type 2 diabetes, cardiovascular disease, cancer and other conditions, the detrimental effect obesity has on people’s health and the pressure placed on healthcare systems is immense. Obesity is a multifactorial condition – numerous factors can influence energy balance2 and therefore a joined up approach is needed for successful prevention and treatment strategies. However, it is also important to better understand the impact of single nutrients on energy balance as this can inform understanding of mechanisms of action, and to this end we support the decision to commission a systematic review of the effect of dietary free sugars on obesity risk. Dental caries is also of public health concern, despite the improvements in dental health mentioned in the report. As well as the pain and expense of treating dental caries, tooth loss and poor oral health can be barriers to consuming a varied diet, particularly in older adults3. Again, we support the decision to commission a systematic review to explore the effects of free sugars consumption on risk of dental caries although we suggest this should have considered frequency of sugars consumption as well as quantity. We also welcome the use of the GRADE assessment system in determining the quality of the evidence used.
Summary of evidence: body weight
The systematic review used as the basis of this section makes a welcome contribution to the body of evidence on the effect of sugars on body weight, which remains inconsistent in strength and conflicting. We note that this review finds a relationship between sugars intake (both increases and reduction) and statistically significant, although relatively small (0.75-0.8kg), changes in body weight in adults and that the evidence was classified as of ‘moderate quality’. In children the evidence related principally to sugar-sweetened beverages. The review states that there was heterogeneity in the studies and that compliance in studies aiming to reduce consumption was often poor. Overall the review found that those children with the highest consumption of free sugars had a significantly higher risk of obesity. In children, the evidence with regard to reduction of free sugars (generally in beverages) and reduction of body weight was classified as ‘moderate’ and the evidence for an increase in free sugars intake and increased body weight was classed as ‘low’.
To inform the future application of the recommendations, it would have been useful to draw out from the review more detail about the amount and/or type of sugars consumption (increases or decreases in intake) that has a measureable effect on body weight.
Another finding of the systematic review was that when diets are isoenergetic, no effect of sugars intake on bodyweight was shown and so it was concluded that the mechanism for weight gain was an excess of calories rather than any physiological or metabolic effect of sugars per se. Given the focus of the guideline on prevention and control of obesity, this finding warrants further discussion. It is important to understand whether increase or reduction of dietary free sugars will directly affect body weight in the context of free living individuals who are not part of a study intervention. If one food or ingredient is removed from the diet then it is generally replaced with another, which may or may not result in a change in energy intake. In the case of sugar-sweetened soft drinks for example, substitution with a sugar-free alternative will avoid addition of extra calories and reduce energy intake (assuming the rest of the diet does not change). However, for other foods, simply opting for reduced sugar or sugar-free versions may not have the desired effect on energy balance because their calorie content may not be significantly different. Taking the example of breakfast cereals, a cereal with no added sugar will have an almost identical calorie content per 100g to an equivalent sugared version and the energy content may actually increase if sugars are removed and the proportion of fat in the cereal increases e.g. if nuts or seeds are added. This may need careful communication when disseminating the guideline.
Summary of evidence: dental caries
We welcome the publication of a systematic review in this area, which helps to inform the evidence base on sugars and dental health. Clearly the systematic review was undertaken with a specific remit to investigate the effect of quantity of sugars intake, in particular below 10% and 5% of energy intake. However, given the large body of evidence on the importance of frequency of sugar intake (e.g. Moynihan and Peterson 20044), it is surprising that this was not considered as part of the development of these guidelines. We note that the evidence for maintaining the current recommendation that free sugars should provide no more than 10% total energy intake is based on 5 studies which were collectively rated by the GRADE process as ‘of moderate quality’.
We note that the basis of the conditional recommendation to limit sugars intake to less than 5% energy intake is just 3 ecological studies, all conducted in children in Japan in 1959 and 1960 with low exposure to fluoride. The quality of this evidence was described by the GRADE process as ‘very low’. It is therefore surprising that this evidence should be used as the sole basis of a worldwide public health recommendation, albeit a conditional recommendation, and in this context welcome the opportunity for the relevance of this evidence to be debated in the consultation.
It is important that the interpretation of science into public health recommendations is transparent and evidence-based. Although there is a summary of considerations in annex 8, it would be helpful to understand more about the process used by WHO to determine recommendations and the basis for their classification. The evidence base used to make the two ‘strong’ recommendations was classified as of ‘moderate quality’. Is ‘moderate quality’ evidence the threshold level for giving strong recommendations? This is important in interpreting the recommendations as, without reference back to the description of the evidence base in the systematic review, a ‘strong’ recommendation might be assumed to be based on ‘strong’ or ‘high quality’ evidence. We would make a similar comment on the ‘conditional’ recommendation in this document. It might be assumed that this would be based on evidence of moderate quality whereas in fact the evidence base for this recommendation is classified as of ‘very low’ quality. Again it would be useful to understand the threshold level of evidence to give a ‘conditional’ recommendation, whether ‘very low’ quality evidence is generally considered sufficient to support recommendations and how this compares to the level of evidence that supports other public health recommendations by the WHO and other national or international bodies.
WHO recommends reduced intake of free sugars throughout the life-course (strong recommendation).
It would be useful to have some more context for this recommendation in order to determine how it should be applied in practice and whether it applies equally to populations with higher and lower intakes? Is there any threshold beneath which this would not apply? Does the source of the free sugars need to be considered?
WHO suggests further reduction below 5% of total energy (conditional recommendation)
As mentioned in our response in the previous section, the evidence used as the basis of this recommendation has been classified by the GRADE process as of ‘very low’ quality. While we understand that this recommendation has been classified as conditional, the fact that it is listed as a WHO recommendation along with the other two ‘strong’ recommendations in this document gives it a weighting that the evidence seems not to merit and that this may cause confusion when it comes to applying the recommendations. Indeed, in media coverage in the UK the recommendation was reported in a manner disproportionate to the ‘conditional’ tag and also reported as if it was based on evidence relating to weight management rather than solely on the dental health literature.
The 3rd remark states that “these recommendations were based on the totality of evidence regarding the relationship between free sugars intake, and body weight and dental caries”. However, it is then stated that the recommendations to reduce free sugars to below 10% and 5% of energy intake respectively are both based only on studies with dental caries as an outcome. It is unclear therefore to which recommendation this remark refers – is it only to the first recommendation around reducing intake of free sugars over the life course? The evidence on the relationship between sugars intake and body weight is complex and often contradictory. The systematic review of the effect of sugars consumption on body weight used for this guideline found that for isoenergetic diets no effects of sugars intake on body weight were detected. It was concluded that the mechanism for the association between sugars intake and body weight was mediated via positive energy balance. Therefore, if this evidence is used as the basis of recommendations it is important that the concept of energy balance in relation to sugars consumption is also communicated.
In the remarks relating to the evidence base for the guideline, there is no mention of the GRADE classification of the evidence. This is an important piece of information to include with the remarks to inform the reader (especially those who may not read the full guideline) about the strength of the evidence on which the recommendation was made. The simple statements relating to the evidence for body weight and dental health in remarks 4-7 may suggest that the evidence is clear and unequivocal, which is not the case in such complex relationships between diet and health, particularly in relation to the recommendation on reducing sugars intake below 5% total energy.
Research gaps and future initiatives: implications for future research
We note that in the area of sugars and body weight, only one systematic review was used as the basis of these guidelines but we would highlight the availability of other substantial reviews of the evidence in this area for consideration, for example by EFSA5 and the German Nutrition Society6. The UK Scientific Advisory Committee on Nutrition will also publish a report on dietary carbohydrate and health later this year, compiled using systematic reviews, which may also provide some useful perspectives for this guideline.
We welcome the suggestion for further research in the areas of free sugars, body weight and dental health. We would encourage WHO to consider research that looks at the effect of dietary patterns in relation to free sugars consumption rather than focussing on sugars as a nutrient in isolation. Free sugars can be found in a wide range of foods, with a variety of nutrient profiles that can affect health in different ways, both positively and negatively. The focus on sugars in isolation, which was particularly highlighted in the consumer media in the UK after this draft guideline was published, without consideration of the balance of the diet as a whole, does not seem helpful for the general public, and guidance on the balance of foods that constitute a healthy diet is likely to be more actionable by individuals and arguably more likely to have a tangible public health benefit.
Any additional comments
The conditions considered by this guideline - obesity and dental caries - are of great importance for global public health and hence it is imperative that we understand more about the development of these conditions so that we can improve strategies for prevention and treatment. We particularly welcome the use of systematic reviews to explore the evidence base as these have the potential to provide a high quality basis for public health recommendations. However, it would be helpful to understand more about the process WHO has used in translating the ‘risk assessment’ evidence base derived from the systematic reviews into recommendations (for risk management). In particular, it would be helpful to have clarity on the process by which the recommendations have been classified as ‘strong’ or ‘conditional’ and the level of evidence required for each, given that the relationships that support the recommendations were typically of no more than moderate strength in the systematic reviews.
1 WHO factsheet: obesity and overweight, 2013. http://www.who.int/mediacentre/factsheets/fs311/en/
2 Foresight. Tackling obesities: future choices. Project report. http://www.bis.gov.uk/assets/foresight/docs/obesity/17.pdf
3 Walls A (2009) Healthy Ageing: Teeth and the oral cavity. In: Healthy Ageing – The Role of Nutrition and Lifestyle. Report of the British Nutrition Foundation Task Force. Wiley-Blackwell, Oxford
4 Moynihan & Peterson (2004).Diet, nutrition and the prevention of dental diseases. Public Health Nutrition: 7(1A), 201–226 http://www.who.int/nutrition/publications/public_health_nut7.pdf
5 EFSA (2010) Scientific Opinion on Dietary Reference Values for carbohydrates and dietary fibre EFSA Journal 2010; 8(3):1462 [77 pp.]. http://www.efsa.europa.eu/en/efsajournal/pub/1462.htm
6 Hauner et al. (2012) Evidence-Based Guideline of the German Nutrition Society: Carbohydrate Intake and Prevention of Nutrition-Related Diseases. Ann Nutr Metab 2012;60(suppl 1):1–58 http://www.karger.com/Article/FullText/335326