The UK soda tax (Soft Drinks Industry Levy, SDI), implemented in April 2018, has emerged as a cornerstone policy in the global effort to curb free sugar consumption and combat Non-Communicable Diseases (NCDs).
A groundbreaking study by Rogers et al., (2024) offers the first individual-level analysis of the soda tax impact on dietary free sugar consumption, drawing on data from the UK National Diet and Nutrition Survey (NDNS).
The findings reveal significant reductions in free sugar intake, particularly from soft drinks, underscoring the effectiveness of fiscal policies in promoting healthier dietary habits.
Background and objectives
Excessive consumption of free sugars is a well-documented driver of NCDs, including obesity, type 2 diabetes, and cardiovascular diseases. Both the World Health Organization (WHO) and the UK Scientific Advisory Committee on Nutrition (SACN) recommend limiting free sugar intake to less than 5% of total energy intake. Also stimulating EFSA to revise its opinion on added sugars, in 2022.
Despite these guidelines, free sugar consumption in the UK as elsewhere has historically exceeded recommended levels, with sugar-sweetened beverages (SSBs) being a major contributor, especially among children and adolescents. With a tremendous impact on diabetes and cardiovascular disease (Lara-Castor et al., 2025). The UK soda tax, announced in March 2016 and implemented in April 2018, was designed to incentivise manufacturers to reduce the sugar content of soft drinks.
This study aimed to evaluate changes in free sugar consumption at the individual level, both from soft drinks and across the entire diet, following the introduction of the soda tax.
Methodology
Researchers employed a controlled interrupted time series (ITS) analysis, leveraging data from the NDNS spanning 2008 to 2019. The NDNS is a continuous, nationally representative survey that captures food and drink consumption both inside and outside the home. The analysis included 7,999 adults and 7,656 children, with dietary data collected through 3- or 4-day food diaries.
Key outcomes measured were absolute and relative changes in free sugar consumption from soft drinks alone and from all food and drinks combined, as well as the percentage of total energy derived from free sugars. Protein consumption was used as a non-equivalent control to account for confounding factors, such as changes in food prices, that could influence dietary patterns independently of the SDIL.
The ITS analysis compared observed data with a counterfactual scenario, which modelled what would have happened without the soda tax, using trends from April 2008 to March 2016 (pre-announcement) as the baseline.
Results
The study revealed significant reductions in free sugar consumption following the soda tax implementation. Among children, there was an absolute reduction of 3.0 g/day (95% CI: 0.1 to 5.8) in free sugar consumption from soft drinks alone, representing a 23.5% decrease. For adults, the reduction was even more pronounced, with an absolute decrease of 5.2 g/day (95% CI: 4.2 to 6.1), equating to a 40.4% reduction.
When considering total dietary free sugar consumption, children experienced an absolute reduction of 4.8 g/day (95% CI: 0.6 to 9.1), or a 9.7% decrease, while adults saw a reduction of 10.9 g/day (95% CI: 7.8 to 13.9), representing a 19.8% decrease.
Interestingly, the percentage of total energy derived from free sugars declined over the study period but did not change significantly relative to the counterfactual. This suggests that reductions in free sugar intake were accompanied by simultaneous decreases in total energy intake, highlighting a broader shift in dietary patterns.
Discussion and implications
The findings align with previous research demonstrating that the soda tax prompted significant reformulation of soft drinks, in the UK, as manufacturers reduced sugar content to avoid the levy. The study also corroborates evidence from household purchasing data, which indicated an 8 g/week reduction in sugar purchased from soft drinks post-SDIL (soda tax).
The authors underscore several key implications. First, the soda tax has contributed to meaningful reductions in free sugar consumption, particularly from soft drinks, which are a major source of added sugars in the diet. Second, the findings reinforce the efficacy of fiscal policies, such as sugar taxes, in driving healthier dietary choices. This provides a robust evidence base for extending or considering similar policies targeting other high-sugar products. Third, the lack of significant substitution with other sugary foods or drinks suggests that the SDIL successfully reduced overall sugar intake without unintended dietary shifts.
However, despite these reductions, free sugar consumption remains above the WHO’s recommended 5% of total energy intake. This highlights the need for continued efforts, including potential expansion of fiscal policies and public health campaigns, to further reduce sugar consumption and address the growing burden of NCDs.
Strengths and limitations
The study’s strengths lie in its use of nationally representative data collected consistently over 11 years, providing a comprehensive view of dietary habits both inside and outside the home. The inclusion of protein consumption as a control strengthens the analysis by accounting for confounding factors such as changes in food prices.
However, it could not fully account for other interventions, such as the UK’s voluntary sugar reduction programme, which in theory may have influenced dietary trends independently of the soda tax. Additionally, self-reported dietary data may be subject to under-reporting, particularly for high-sugar foods, which could affect the accuracy of the findings.
Conclusion
The UK soda tax has proven effective in reducing free sugar consumption, particularly from soft drinks, in both children and adults. While energy from free sugars as a proportion of total energy did not change significantly, the reductions in absolute sugar intake represent a positive step towards improving public health.
The study provides compelling evidence for the role of fiscal policies in addressing dietary-related NCDs and offers a strong foundation for future interventions aimed at promoting healthier diets, including front-of-pack nutrition labelling systems such as Nutri-Score.
Dario Dongo
References
(1) Rogers NT, Cummins S, Jones CP, et al., (2024). Estimated changes in free sugar consumption one year after the UK soft drinks industry levy came into force: controlled interrupted time series analysis of the National Diet and Nutrition Survey (2011–2019). J Epidemiol Community Health. 2024. DOI: 10.1136/jech-2023-221051.
(2) World Health Organization. Guidelines: Sugars intake for adults and children. 2015. Available: https://www.who.int/publications/i/item/9789241549028.
(3) Scientific Advisory Committee on Nutrition. Carbohydrates and health. 2015. Available: https://www.gov.uk/government/publications/sacn-carbohydrates-and-health-report.
(4) EFSA Panel on Nutrition, Novel Foods and Food Allergens (NDA), Turck, D., Bohn, T. et al. (2022) ‘Tolerable upper intake level for dietary sugars’, EFSA Journal, 28 February. Available at: https://doi.org/10.2903/j.efsa.2022.7074.
(5) Lara-Castor, L., O’Hearn, M., Cudhea, F. et al. and Global Dietary Database (2025). ‘Burdens of type 2 diabetes and cardiovascular disease attributable to sugar-sweetened beverages in 184 countries’, Nature Medicine. Available at: https://doi.org/10.1038/s41591-024-03345-4.
(6) Teng AM, Jones AC, Mizdrak A, et al. Impact of sugar-sweetened beverage taxes on purchases and dietary intake: systematic review and meta-analysis. Obes Rev. 2019;20(9):1187–1204. DOI: 10.1111/obr.12868.
(7) Scarborough P, Adhikari V, Harrington RA, et al. Impact of the announcement and implementation of the UK soft drinks industry levy on sugar content, price, product size and number of available soft drinks in the UK, 2015–19: a controlled interrupted time series analysis. PLoS Med. 2020;17(2):e1003025. DOI: 10.1371/journal.pmed.1003025.
(8) World Health Organization (2024). Fiscal policies to promote healthy diets: WHO guideline. Geneva: World Health Organization. ISBN: 978-92-4-009101-6
(9) Crosetto, P., Muller, L. and Ruffieux, B. (2024). ‘Label or taxes: why not both? Testing nutritional mixed policies in the lab’, Journal of Economic Behavior and Organization. Available at https://doi.org/10.1016/j.jebo.2024.106825
Dario Dongo, lawyer and journalist, PhD in international food law, founder of WIISE (FARE - GIFT - Food Times) and Égalité.
