“Sugar intake must be slashed further,” reports BBC News today.
The news reports follow an ecological study estimating the burden of disease caused by sugar-related tooth decay in adults and children across a life course, in a number of different countries.
It calculated that the burden would be significantly reduced by setting a target limit of less than 3% of total energy intake from sugar. This is much lower than the current figure outlined by the World Health Organization (WHO), which says that sugars should be less than 10% of a person’s daily calorie intake.
This reassessment of the target figure is not official from either the WHO or Public Health England, but has led to widespread media reports stating, “action needed to curb sugar” (Mail Online), while others have outlined possible sugar bans in schools and hospitals (The Daily Express and The Daily Telegraph) or sugar-related taxes. These angles were not put forward in the academic publication, which only suggested new, lower targets for sugar intake should be developed. It did not specify how to achieve them.
Potential limitations of the study include the accuracy of the sugar intake estimates and the percentage of total intake derived from sugar. This may or may not affect their overall conclusion that the existing target, of less than 10%, should be lowered.
On its own, this study does not appear robust enough to lead to policy changes.
Where did the story come from?
The study was carried out by researchers from University College London, who reported that no external funds were required for these analyses, interpretation or the writing of the paper.
The reporting of the study was generally accurate across media outlets, with most coverage bringing in other issues around sugar bans, sugar taxes and other potential control measures in schools. These were not proposed in the original publication, so their source is unclear.
What kind of research was this?
This was an ecological study of national data on sugar intake and dental decay in many countries around the world, to assess the burden of disease in adults and children.
Tooth decay is a common problem that occurs when acids in your mouth dissolve the outer layers of your teeth. It is also known as dental decay, tooth decay or dental caries. Although levels of tooth decay have decreased over the last few decades, it is still one of the most widespread health problems in the UK.
Sugar is a known cause of tooth decay, but the research team say no analysis has been made of the lifetime burden of dental decay by sugar. They wanted to estimate this and also see whether the WHO goal of less than 10% of total energy intake from sugar is optimal and compatible with low levels of dental decay.
What did the research involve?
The study gathered information on the prevalence and incidence of dental caries from nationally representative datasets. They then looked for links with national estimates of sugar intake from dietary surveys, or from the national intake assessed from the UN Food and Agriculture Organization Food Balance Sheet.
Analysis looked at countries where sugar intake had changed due to wartime restrictions or as part of a broader nutritional transition linked to becoming a more industrialised nation. The main analysis established a dose response relationship between sugar consumption and risk of dental decay across a life course. This was different to many previous studies that focused on the impact in children only. The impact of fluoride, in the water supply or applied through toothpaste, on the dose response relationship was also considered.
Sugar intake was defined differently in different national dietary surveys, but generally referred to sucrose consumption, often termed “non-milk extrinsic sugars”. In the US, fructose syrups are included, and in the UK, the term “non-milk extrinsic sugars” is used to define these non-lactose disaccharides, with maltose making a negligible contribution. The statistics do not take account of sugars contained in dried fruit.
Estimates of national sugar consumption were used to calculate the proportion of total energy a person might be getting from sugar each day, and were based on an estimate of average global energy intake (men, women and children) of 2,000 calories per day.
What were the basic results?
Detailed information from Japan indicated sugar was directly related to dental decay when sugar increased from 0% to 10% of total daily energy intake. This led to a 10-fold increase in dental caries over several years.
Adults aged over 65 had nearly half of all tooth surfaces affected by caries, even when they lived in water-fluoridated areas, where high proportions of people used fluoridated toothpastes. This did not occur in countries where the intake of sugar was less than 3% of total daily energy intake.
Therefore, the cut-off they calculated to reduce the burden of disease caused by sugar was a daily intake of less than 3% of total energy intake. They suggested that less than 5% might be a more pragmatic target for policy makers. The current WHO recommendation is less than 10%.
How did the researchers interpret the results?
The researchers concluded that, “there is a robust log-linear relationship of [dental] caries to sugar intakes from 0% to 10% sugar [of total energy]. A 10% sugar intake induces a costly burden of caries. These findings imply that public health goals need to set sugar intakes ideally <3%, with <5% as a pragmatic goal, even when fluoride is widely used. Adult as well as children’s caries burdens should define the new criteria for developing goals for sugar intake.”
This ecological study looked at national data sets to estimate the burden of disease caused by sugar-related tooth decay in adults and children across a life course. It calculated that the burden would be significantly reduced by setting a target limit of less than 3% of total energy intake coming from sugar. This is much lower than the current figure outlined by the WHO, which states that sugar should be less than 10% of a person’s daily calorie intake.
This reassessment of the target figure is not official, but has led to widespread media reports stating, “action needed to curb sugar” (Mail Online), with others outlining possible sugar bans in schools and hospitals (Express and Telegraph) or sugar-related taxes. These angles were not put forward in the academic publication, which only went as far as suggesting that new, lower targets for sugar intake should be developed. They did not specify how the reduction could or should occur.
The study has many potential limitations, thereby reducing its reliability and calling into question the precision of its estimates and the 3% cut off. Namely, it is likely to include inaccuracy in its estimates of sugar intake and particularly the percentage of total intake derived from sugar. For this, it used a generic figure of 2,000 calories per day for men, women and children. This may not be an accurate representation of intake present across a very diverse demographic of people from a range of different countries.
The severity of the health effects of sugar has long been debated and was somewhat popularised in the 1972 book “Pure White and Deadly” by Professor John Yudkin. Discussions since then have considered whether more restrictions should be placed on sugar, given the many estimates of its widespread negative effect on health in terms of weight gain, tooth decay, diabetes and contribution to other diseases.
This has also included debate around whether the food and drinks industries should do more (through voluntary or mandatory mechanisms) to reduce the sugar content of their products, particularly those marketed at children, in a similar vein to efforts to reduce the salt and saturated fat content of food in the 1980s and 90s.
On its own, this study does not appear robust enough to lead to policy changes; however, the debate is clearly underway, as some media reports indicated both the WHO and advisors in England may be considering a cut in their recommendations for sugar consumption.
These considerations are likely to be based on much stronger or broader evidence than this single study.