The latest study of the effects of the soft drinks industry levy (SDIL), introduced in 2018 and popularly known as the 'sugar tax', showed it was associated with significant reductions in the consumption of free sugars, not only from soft drinks but also across the diet as a whole.
Researchers led by Dr Nina Trivedy Rogers of the MRC Epidemiology Unit at the University of Cambridge stated that their study was the first to examine changes in individual-level consumption of free sugars in relation to the SDIL.
She told Medscape News UK that the team's previous research had demonstrated a correlation between the SDIL and a reduction in obesity among older primary school girls, purchases of sugar sweetened beverages (SSBs), and childhood hospital admissions for dental extractions. Additionally, her team's findings, reported in Nature Communications last month, indicated a decrease in hospitalisations for childhood asthma, a condition that has been linked to SSB consumption.
Sugar Tax Recommended to Improve Population Health
Rogers said that while the sugar tax "is not a silver bullet", it has been shown to be successful in terms of a range of benefits. "I would recommend that it be used alongside a raft of public health prevention measures to improve population health."
The latest study, published in the Journal of Epidemiology & Community Health, used data from the UK National Diet and Nutrition Survey for a nationally representative sample of 7999 adults and 7656 children for the 11 months after SDIL implementation. Using a controlled interrupted time series for 2011 to 2019, they modelled the effects of the levy on absolute and relative changes in total intake of dietary free sugars from all food and soft drinks combined, and from soft drinks alone. The analysis was based on the period January to March 2019, with comparisons made to what would be expected had the SDIL not been introduced.
The results showed that daily sugar intake fell by around 5 g in children (relative reduction 10%) and 11 g in adults (relative reduction 20%), even after accounting for previously declining trends in dietary free sugar intake. Estimates suggested that sugar from soft drinks alone made up around half of this total, approximately 3 g daily in children (relative reduction 23.5%) and 5 g in adults (relative reduction almost 40.5%).
Protein intake, as a nonlevy comparator subject to other contemporaneous factors such as increases in food prices, remained stable throughout the study period.
Reductions in dietary sugar after the SDIL "may have driven significant reductions in overall energy", the team commented. Nevertheless, daily energy intake from free sugars was still higher than the 5% recommended by the World Health Organisation (WHO), equivalent to 30 g/day for adults, 24 g for 7-10 year olds, and 19 g for 4-6 year olds.
Longer-Term Effects Could Boost Life Expectancy
At some point a "floor effect" will emerge, according to Rogers. The reduction of sugar in beverages with minimal sugar content will slow down due to the limited scope for further reduction. Nevertheless, the study showed "continued declines in sugar consumption from soft drinks with no flattening or change in direction at the one year mark".
We can't be certain about long-term trends in calorie intake, Rogers said. However, "our findings suggest that other high calorie foods were not consumed as potential substitutes during the study period".
The team's more recently published paper showed that at 19 months after the SDIL imposition, there were still "sustained reductions in purchasing of sugar from soft drinks", and they anticipated potential long-term improvements in life expectancy.
SSB Taxes Now Among "The Most Evidence-based Policies"
Asked to comment by Medscape News UK, Professor Franco Sassi, director of the Centre for Health Economics and Policy Innovation at Imperial College Business School, said this is only the last in a series of papers that have shown positive effects of the SDIL. "SSB taxes are now among the most evidence-based policies to incentivise healthy diets."
Sassi was a member of the technical committee that produced WHO guidelines launched in June for using food and beverage taxation to promote healthy diets to curb obesity and diet-related chronic noncommunicable diseases. He explained: "Taxes on SSBs typically reduce the consumption of taxed drinks in the same proportion as the price increase." Well-designed taxes, like the SDIL in the UK, can push beverage manufacturers to reduce sugar levels "and also increase awareness about the contribution of sugar and sugar-sweetened beverages to poor health".
Should Taxes Have a Wider Reach?
Taxes seem to reach the parts that other efforts can't. Research led by Dr Kawther Hashem, lecturer in public health nutrition at Queen Mary University of London, demonstrated that the SDIL achieved a reduction in total sugar sales of 34.3%, compared with only 3.5% from the previous voluntary reduction programme, despite a target of 20% for both.
"The SDIL in the UK has proven to be an effective lever to encourage food and drink manufacturers to reduce sugar," she told Medscape News UK. Rogers' team had noted that while soft drinks are the largest single source (29%) of free sugars for the 11-18 age group, in 4-10 year olds the largest single contributor is cereal and cereal products, followed by soft drinks and fruit juice. For adults the largest source is sugar, preserves, and confectionery, followed by nonalcoholic drinks.
Hashem urged policymakers to consider applying a similar levy to other discretionary products that are key contributors to sugar intake, such as chocolate confectionary. "Without doubt, unhealthy diets are the biggest cause of death and disability globally, and cost the UK more than £100 billion annually," she said.
Levy "An Enormous Success"
Asked to comment by Medscape News UK, Katharine Jenner, director of the Obesity Health Alliance, told us: "This welcome new analysis adds to the huge body of evidence that the SDIL has been an enormous success," she said. As well as reducing sugar consumption, the levy also raises between £300 and £350 million a year, which was used to establish the National School Breakfast Programme and to double the school sports premium.
"The world we live in doesn’t make it easy to be healthy, and there is no silver bullet to fixing our broken food system," she said. "Instead, it takes a range of measures such as extending the SDIL to other high sugar foods and restricting advertising and promotion of unhealthy foods, all working at once to encourage the food industry to adapt their recipes.
"This new research should give hope to the new government that, with the right levers, it is possible to improve the nation’s health."
The study was funded by the NIHR Public Health Research programme.