The Soft Drinks Industry Levy (SDIL) set to be introduced by the UK Government may have the unintended effect of increasing consumer consumption of alcohol, according to new research carried out by the London School of Hygiene and Tropical Medicine, Oxford University and Cambridge University.

The report published in the Journal of Epidemiology and Community Health was based on consumer data from Kantar Worldpanel which detailed household expenditure on food and drink in 2012 and 2013 from a national representative sample of 32,000 UK households.

The data included six million drinks purchases and incorporated 11 types of drinks: high-, medium- and low-sugar drinks, fruit juices, milk-based drinks, water, beer, lager, cider, wines and spirits.

It shows that increasing the price of medium-sugar drinks reduces the purchase of beers, lagers and wine across all income groups. Whereas increasing the price of low-sugar drinks causes an increase in the purchase of all drinks other than high- and medium-sugar drinks. Finally, raising the price of high-sugar drinks leads to an increase in the purchase of diet beverages, juices and lager, but a decrease in the sales of medium-sugar drinks and spirits.

The report concluded that increasing the price of soft drinks may alter purchase patterns for alcohol. Also, the evidence suggests that increasing the price of medium-sugar drinks could have multiple benefits as it could reduce the sales of alcohol–whilst the reverse is true when prices of low-sugar drinks are increased.

In terms of sugar taxation policy, the researchers state: “Increasing the price of [sugar-sweetened beverages] has the potential to both increase and decrease the purchase of alcohol, suggesting more nuanced price options across a range of beverages may be more effective than a single tax on high-sugar [ones].”

Lead researcher, Professor Richard Smith, dean of the Faculty of Public Health and Policy, London School of Hygiene and Tropical Medicine, said: “Taxing soft drinks may affect alcohol consumption because increasing the price of one type of product may also affect purchases of other more or less similar products as the relative prices change.

“This study indicates varied responses in alcohol purchases for at-home consumption if prices of soft drinks change. Particularly the study finds a strong case in ensuring that diet drinks are excluded from price increases to avoid increases in alcohol purchases. Although the study design does not allow us to disentangle the reasons for such associations, the evaluations of fiscal interventions should carefully monitor changes in wider outcomes not just immediate substitutes among non-taxed beverages such as water or fruit juice.”

The researchers acknowledge that further inquiries would need to be undertaken to understand the reasoning behind these purchasing habits, saying: “Although this analysis can highlight significant relationships between beverages purchased, it cannot explain why these relationships arise. This mixed picture indicates the complexity of estimating the impact of a single price increase.”

The SDIL was announced by former Chancellor of the Exchequer George Osbourne in his 2016 Budget speech as part of the UK Government’s child obesity strategy. It is a two band levy: the first band is relevant to drinks with more than 5mg of sugar per 100ml of liquid; the second band is for drinks with more than 8mg per 100ml. It is set to be introduced in April 2018.

The UK will not be the first country to introduce a ‘sugar tax’ as the SDIL has become known in the media. As part of efforts to combat health problems like obesity and type-2 diabetes, countries including Mexico, Thailand, Saudi Arabia, Hungary and France have already implemented a taxation on sugar-sweetened soft drinks.