October 16, 2017

expert reaction to study looking at sugary drinks levy and sales of sugary drinks in jamie’s italian restaurants

Publishing in the Journal of Epidemiology & Community Health, researchers have evaluated the changes in sales of non-alcoholic beverages in Jamie’s Italian restaurants in the UK following the introduction of the sugar tax on sugar sweetened drinks.

Prof. Susan Jebb, Professor of Diet and Population Health, University of Oxford, said:

“This study provides the first evidence in the UK of the effects of a price rise on sales of sugar-sweetened beverages in a restaurant setting.  Given the ‘real-world’ implementation of this initiative the study is based on a pragmatic interrupted time series rather than a stronger research design, so findings are indicative rather than conclusive.

“Nonetheless this is a careful analysis and shows a greater than anticipated fall in sales which is encouraging news for public health ahead of the introduction of the soft drink industry levy next year.  Surprisingly, and unlike the experience in some other countries, there was also a decline in low- and no-sugar drinks which is harder to explain.  The gap in the paper is data on alcohol sales, since any compensatory increase (which may or may not have occurred) would be of considerable concern given the potential contribution to energy intake and health harms.  Businesses will also want to understand more about the likely impact on turnover.”

Prof. Richard Tiffin, Professor of Applied Economics and Director of the Centre for Food Security, University of Reading, said:

“This study is in line with earlier studies in which changes in purchases match the price increase.  These are quite large price increases, and the changes in consumption are not sufficient to have a meaningful impact on obesity.  Measures that are specifically targeted at those with the worst diets are likely to be more effective.”

Prof. Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said:

“This study needs careful interpretation.  It does provide good statistical evidence that the pattern of consumption of non-alcoholic drinks in Jamie’s Italian restaurants changed after the beginning of September 2015.  That was that date that the 10 pence levy on sugary drinks was introduced.  But even though the title of the paper and the top lines of the press releases don’t mention it, the study and the content of the press releases make it clear that there was a lot more going on than just the price increase.  The menu was redesigned, it explained that the proceeds of the levy would go to a Children’s Health Fund, new drink products were introduced, and Jamie himself appeared in a television programme about sugar.  So we certainly can’t be sure that the fall in consumption of sugary drinks was entirely, or even mainly, caused by the extra 10p.

“The researchers do provide some circumstantial evidence that the 10p played a role in the reduction in consumption, but they (rightly) make it clear that a study like this can’t prove what caused what.  Actually it doesn’t even establish that any of the specific changes at Jamie’s Italian restaurants had anything to do with the lower consumption – for instance, the researchers had no data from any other restaurants, and maybe consumption fell there as well.  Jamie Oliver isn’t the only person to have been on TV pointing out the health consequences of too much sugar, and the general publicity that sugary drinks are bad for health is likely to have had some general effect on consumption.

“It’s interesting that, in this study, the consumption of fruit juice from the children’s menu fell as well – indeed it fell by rather more than the consumption of the sugar-sweetened drinks, while consumption of fruit juice from the main menu went up.  Maybe the numbers of children going to the restaurants changed, relative to the numbers of adults – the researchers couldn’t tell because they had no data on whether customers were adults or children.  Maybe things would have been clearer if they had had data over a full year after the change, rather than just from September to February.

“It certainly seems plausible to me that these changes at Jamie’s Italian restaurants did cause a reduction in consumption of sugary drinks, and that the 10p levy played an important role – but there’s a big difference between plausibility and convincing scientific evidence, and I support the researchers’ call for more investigation, in other restaurants, and with a longer follow-up period, to try to pin down more clearly what really works.”

* ‘Change in non-alcoholic beverage sales following a 10-pence levy on sugar-sweetened beverages within a national chain of restaurants in the UK: interrupted time series analysis of a natural experiment’ by Laura Cornelsen et al. was published in the Journal of Epidemiology & Community Health on Monday 16 October 2017.

Declared interests

Prof. Susan Jebb: “Prof Susan Jebb is employed by the University of Oxford and receives no personal funding from the food industry.  Susan Jebb is conducting research into the treatment of obesity, some of which include support from WeightWatchers, Slimming World and the Cambridge Weight Plan.  Susan was the independent Chair of the Public Health Responsibility Deal Food Network and was a science advisor to the Foresight obesity report.  From 2007-10 she was the principal investigator for a research study funded by the food industry to investigate the potential for a functional beverage to help weight loss.  The results of this work have been published: http://www.ncbi.nlm.nih.gov/pubmed/23920353”

Prof. Richard Tiffin: “I am Science Director of Agrimetrics, a government-funded data centre that works with businesses across the food system. I have been involved for many years in UK research council and industry-funded studies into the effects of taxation on patterns of consumption, including one study that was funded by a soft drinks manufacturers’ association.”

Prof. Kevin McConway: “I am about to become a member of the Science Media Centre Advisory Board.”