Oops: A Retraction on UK Soft Drink Taxes

An amicable discussion about evidence for the effectiveness of soft drink taxes can be, well, somewhat taxing. Scientists with genuine curiosity about this subject often seem harder to find than true believers. But disappointment has come for those true believers. Because some of the evidence to back their firm beliefs in soft drink taxes recently crumbled in the UK. The BMJ this month retracted a 2021 paper, explaining:

“The authors identified an error in the paper that, when corrected, altered the main messages of the paper.

“The authors themselves identified the problem and alerted the journal and readers about inaccuracies arising from the way in which the data were prepared for analysis.”

Errors Multiply

Back in 2021 when this paper was first published, soda tax fans greeted it enthusiastically. The authors were claiming a ten percent reduction in sugar consumed from soft drinks by UK households. “UK’s sugar tax hits the sweet spot,” wrote Alexandra Jones, Jason Wu, and Kent Buse in a BMJ editorial at the time. Now, BMJ has retracted that editorial, too.

No matter. There are plenty more articles still pushing the message that these soft drink taxes work well in the UK. In fact, earlier this year, some of the same authors from the now retracted article published an analysis of the association between implementation of the UK tax and the prevalence of obesity in primary school children.

As we noted at the time, they made some rather bold claims about “positive health impacts” even though they could only find a correlation in girls aged 10-11 years. But that was enough to generate headlines saying the “soda tax slashes obesity rates in young girls.”

In making the leap from a correlation to inference of causation, those authors cited the now retracted analysis of an association between the tax and soda consumption as support for plausibility. In this way, the false conclusion in the retracted article lives on through another publication.

Party Poopers Sending the Wrong Message

When we point out these leaps of faith, the believers express annoyance. “I am worried that you are sending the wrong message,” said wrote one esteemed researcher when we raised questions about a different study.

We truly do not want to be a party pooper. But we would like to see more critical thinking about the effects of soda taxes on obesity and health. Casting about for data to support a pre-ordained conclusion does not help with the credibility of public health research. Nor does it help us find strategies that will benefit population health.

Click here for more about this retraction, here and here for further perspective.

Soda Fountain, painting by William James Glackens / WikiArt

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December 12, 2023