Statement – 05 December 2023

Correction to: Changes in soft drinks purchased by British households associated with the UK soft drinks industry levy: controlled interrupted time series analysis; BMJ (2021)

David Pell, Oliver Mytton, Tarra L Penney, Adam Briggs, Steven Cummins, Catrin Penn-Jones, Mike Rayner, Harry Rutter, Peter Scarborough, Stephen J. Sharp, Richard D. Smith, Martin White, Jean Adams

This paper was published in The BMJ on 10 March 2021 and described changes in soft drink purchases by British households associated with the UK Soft Drinks Industry Levy (SDIL) one year after implementation. It reported that at 1 year post implementation, the levy was associated with a reduction in household purchasing of sugar from all soft drinks combined of 30g (or 10%) per household per week; and no change in volume of all soft drinks purchased.

During subsequent analysis, we identified that the analysis presented in the original paper contained an error. During preparation for the original analysis, a weighting variable was incorrectly calculated. This variable was also redundant to the analysis replicating a second weighting variable.

The authors alerted The BMJ to this error. The BMJ have now retracted the original paper and published a corrected version in BMJ Open.

The corrected version replicates the original analysis without the redundant and incorrectly calculated weighting variable.

Most of the results in the paper are impacted by the correction – some by a negligible amount, others more substantively. Overall, the estimate of change in purchasing of sugar from all soft drinks combined at 1 year post implementation of the levy reduces from -30g (or -10%) per household per week to -8g (or -3%) per household per week. Alongside, the estimate of change in volume of soft drinks purchases increases from no change to a 189g (or 3%) increase per household per week.

Nevertheless, the authors believe that the results still have important public health implications. The findings indicate that the SDIL may have had a public health benefit (by reducing household purchasing of sugar from soft drinks) without harming, and indeed potentially benefiting, industry (by increasing total volume of soft drinks purchased).

Our wider evaluation has also reported that the SDIL was associated with:

• Limited and short-lived impacts on stock market value of UK-operating soft drinks companies listed on the London Stock Exchange
• A short-term negative impact on the domestic turnover of UK soft drinks manufacturers that did not continue post-implementation
• Reductions in sugar concentration of soft drinks
• Decreased prevalence of obesity in year 6 girls, with the greatest differences in those living in the most deprived areas
• Reductions in incidence rates of childhood hospital admissions for carious tooth extractions across most areas regardless of deprivation status and especially in younger children.
• Acceptance from senior food & drink industry professionals and indications that impacts may extend beyond soft drinks, but frustration that legislation did not adequately reflect the complexity of the sector
• Changing industry reactions reported in the media over time from initial strong opposition to later adaptation and focus on maximising perceived profitability
• Understanding by UK adolescents of the negative consequences of excess sugar and SSB consumption and acceptance of interventions that require little effort from them to benefit
• High support among UK adults that did not change between 4 months before implementation and 8 or 20 months after

We also have a number of further papers under review available in pre-print form which have not yet been through peer review. These indicate that the SDIL was associated with:

• Sustained reductions in sugar derived from soft drink purchases 2y following implementation, with the greatest effects in low-income households and those with children
• Reductions in incidence rates of childhood hospital admissions for asthma across all age and deprivation groups
• Reductions in dietary free sugar consumption in children and adults, as reported in the National Diet & Nutrition Survey
• Meaningful improvements in population health and reductions in health sector spending, from modelling analyses

Reference

• Rogers NT. et al. “Changes in soft drinks purchased by British households associated with the UK soft drinks industry levy: a controlled interrupted time series analysis” BMJ Open (2023) DOI:10.1136/bmjopen-2023-077059

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Original Post – 11 March 2021

The amount of sugar purchased by households through soft drinks fell by 10% in the year following the introduction of the UK Soft Drinks Industry Levy.

While the volume of soft drinks purchased did not change, the amount of sugar in those drinks was 30g lower per household per week, which the researchers say represents a ‘win-win’ for public health and industry.

Sugary drinks have been linked to a number of health issues, including dental caries, obesity, type 2 diabetes and heart disease. In April 2018, the UK introduced a Soft Drinks Industry Levy explicitly designed to incentivise manufacturers to reduce the sugar content of soft drinks. The levy was placed on manufacturers, importers and bottlers rather than on consumers. It included two levy tiers: 24p per litre for ‘high tier’ drinks containing more than or equal to 8g total sugar per 100ml; and 18p per litre for ‘low tier’ drinks containing more than or equal to 5g and less than 8g total sugar per 100ml.

A team led by researchers from the MRC Epidemiology Unit analysed data from the Kantar Worldpanel, in which participating households are asked to record all food and drink purchases brought into the home. This included approximately 31 million purchases of drinks, confectionery and toiletries from March 2014 to March 2019.

The team divided soft drinks into three categories based on sugar content: high tier drinks, low tier drinks and no levy drinks (those with less than 5g total sugar per 100ml). As the Soft Drinks Industry Levy may have led households to substitute other drinks, they also examined purchasing of drinks exempt from the levy, including milk-based drinks, alcoholic drinks and no-added-sugar fruit juices.

The researchers compared purchases in March 2019 against a ‘counterfactual’ estimate – that is, an estimate based on pre-existing trends of how the purchases would look had the levy not taken place at all. This is the first analysis of the impact of the UK Soft Drinks Industry Levy on drink purchases that takes pre-existing trends into account. The results of the study, funded by the NIHR, are published today in The BMJ.

Prior to the introduction of the levy, the volume of high-tier drinks and amount of sugar associated was on a downward trend. However, even taking this trend into consideration, by March 2019, the volume of high tier drinks purchased had fallen by 155ml (44%) per household per week compared to the counterfactual estimate. The amount of sugar purchased in these drinks reduced by 18.0g per household per week, a 46% decrease.

For low tier drinks, the volume of drinks purchased was 177ml (86%) lower per household per week in March 2019 compared with the counterfactual estimate. The amount of sugar fell by 12.5g (an 86% decrease).

Although the volume of no levy drinks purchased didn’t change, as these soft drinks are not sugar-free and some increased in their sugar content, this meant that the sugar purchased from these drinks increased by 15.3g, equivalent to a 166% increase.

Overall, compared to the counterfactual estimate, there was no change in the volume of all soft drinks purchased in March 2019. However, there was a reduction in sugar purchased in all soft drinks (including exempt drinks) combined of 29.5g per household per week, equivalent to a 10% decrease.

The introduction of the Soft Drinks Industry Levy also coincided with significant decreases in purchasing of bottled water. However, the team say this reduction may be due to increases in concern about single-use plastic, which have been attributed, in the UK, to the broadcast of the BBC’s nature documentary series Blue Planet 2.

Dr David Pell, the study’s first author, said:

A 10% drop in the amount of sugar purchased from soft drinks might sound modest, but we know there’s an association between the amount of sugar drinks we consume and the risk of developing conditions such as obesity, type 2 diabetes and high blood pressure. Cutting out even a relatively small amount of sugar should have important impacts on the number of people with obesity and diabetes.”

Professor Martin White, the project lead, added:

The Soft Drinks Industry Levy appears to have led to a reduction in the amount of sugar that people are purchasing in soft drinks without impacting on the overall volume of soft drinks sold. It’s likely that this is due to manufacturers reformulating their products and reducing the sugar concentration in their drinks, as well as to consumers switching to lower sugar alternatives. This represents a valuable win-win for public health and the food industry – potentially improving people’s health with no detrimental effect on the volume of soft drinks that companies are selling.”

Reference

Pell, D et al. Changes in British household purchases of soft drinks associated with implementation of the Soft Drinks Industry Levy: a controlled interrupted time series analysis. BMJ; 11 Mar 2021; DOI: 10.1136/bmj.n254. www.bmj.com/content/372/bmj.n254