Impacts of the United Kingdom’s Soft Drinks Industry Levy: a systems-thinking informed systematic scoping review

Background Consumption of sugar-sweetened beverages (SSBs) is associated with weight, weight gain and incidence of a number of chronic diseases. The World Health Organization recommends taxation on SSBs to reduce consumption. In 2018 the United Kingdom introduced the Soft Drinks Industry Levy (SDIL), a tiered tax on manufacturers and importers of SSBs. We aimed to review the consequences of the SDIL across all potential outcomes, informed by a systems thinking approach, to understand the range and importance of its effects.Methods We undertook a systematic scoping review of empirical studies of the SDIL. We used a conceptual systems map of the hypothesised pathways of effect to inform data extraction and narrative synthesis. Findings are presented in an evidence map and their consistency assessed.Results 38 studies met our inclusion criteria. The SDIL was consistently associated with reformulation of soft drinks to reduce sugar content. It was also consistently associated with: reduced purchasing of sugar from eligible drinks without increasing purchasing of substitute products such as alcohol and confectionary; longer-term improvements in acute and chronic health outcomes; and reduced health and social care costs, with few negative economic impacts for industry.Conclusions By systematically mapping all outcomes evaluated, we have demonstrated the systemic and interconnected impacts of the SDIL. Further research should seek deeper understanding of how to evaluate such interventions as events in complex adaptive systems.Competing Interest StatementMW led and CPJ, MA, HF, JA, HR, AB, SC, OM, TLP, MR, NR, PS and RS contributed to the NIHR funded evaluation of the SDIL (NIHR 16/130/01) and HF, JA and MW co-authored papers from HFs PhD, some outputs from which are included in this evidence synthesis. The authors declare no other interests that may conflict with this study.Clinical Protocols https://osf.io/ztfaw/ Funding StatementThis project was funded by the NIHR Public Health Research programme (Grant Nos. 16/49/01 and 16/130/01). At the time this study was conducted CPJ, MW, RA, JA, MA were also supported in part by: Programme grants to the MRC Epidemiology Unit from the Medical Research Council (grant No. MC_UU_12015/6 and MC_UU_00006/7). MA is supported by the Wellcome Trust (218629/Z/19/Z). The views expressed are those of the authors and not necessarily those of the any of the above-named funders. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesI confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).YesI have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors