Boris Johnson is wrong to worry about a milkshake tax - evidence shows it would work

Boris Johnson claims to have come to the defence of people on low incomes with his plan to put a stop to so-called “sin taxes” on high-sugar, fat and salt foods.

Such government interventions “clobber those who can least afford it”, the Tory leadership candidate said when asked if extending a tax on sugary drinks to milkshakes could help tackle Britain's obesity problem.

Johnson conceded that obesity costs the NHS “absolutely billions” but said he wants evidence that taxes on unhealthy foods "actually stop people from being so fat.”

Well the evidence so far suggests that “sin taxes” do work. We have known for years that large rises in taxes on tobacco - alongside public health campaigns - have been associated with significantly reduced consumption. Now it is becoming clear the same effect happens with unhealthy foods.

In Chile, Mexico, the US and here in the UK, academic research shows that where sugar taxes have been introduced they have lowered consumption of sugary drinks which are known to cintribute to obesity and related illness.

Perhaps more importantly, taxes also change the behaviour of big food businesses, says Professor Corinna Hawkes director of the Centre for Food Policy at City, University of London.

For example, in the UK dozens of drinks have had their formulations changed to reduce sugar to avoid extra tax. As a result we are consuming less sugar without even realising it, says Professor Hawkes.

The UK introduced a tax on sugary soft drinks in April last year which added about 25p to the cost of a 2 litre bottle of Coke.

The early results show that it has had a modest effect in reducing consumption of sugary soft drinks. The effect would likely have been larger if the tax had been larger, says Professor Hawkes.

In the US city of Philadelphia, which put a significantly larger tax of around $1 on a $1.49 bottle of sugary drink in 2017, the results were more marked with sales dropping 51 per cent within the city limits.

Even taking into account those die-hard soda fans who drove out of town to avoid the tax and get their sugar fix, sales dropped 38 per cent.

Total volume sales of taxed beverages in Philadelphia decreased by almost 3 billion litres after the tax was implemented with the average adult reducing the number of times they drink soda by 10.4 times per month.

Of course, this means nothing if people simply replace a drink covered by the tax with something equally unhealthy. On this, the study was less clear-cut, recording a “slight” reduction in overall sugar consumption, with larger reductions for African-American adults.

Chile brought in 18 per cent tax to high-sugar drinks in October 2014 at a time when the country was found to consume more sugary drinks per capita than any other.

Researchers found a “highly significant decrease” of 21.6 per cent in the volume of sugary soft drinks purchased.

Seeing this success, the government went further. In 2016 it put restrictions on cartoon food packaging, stopped schools selling unhealthy foods and banned promotional toys. Foods high in salt, saturated fat, sugar and calories large black cigarette-style warning labels.

Professor Hawkes believes that sugar taxes have also changed behaviour in more subtle ways while shifting the debate onwards and making people think more carefully about their food choices.But what about Johnson’s claim that such taxes “clobber those who can least afford it”? A tax on high-sugar, salt and fat foods will disproportionately hit poorer households because they spend a higher proportion of their income on these items.

But counterbalancing this is the fact that these groups are also far more likely to suffer from diseases caused by these foods and the reduction in quality of life that they bring.

Every week there are 169 amputations due to diabetes, along with 600 strokes, 530 heart attacks and almost 2,000 cases of heart failure.

It is the public purse as a whole that receives the biggest clobbering from this with the cost to the NHS predicted to soar to £17bn. A 2011 estimate put the cost to the wider economy at £23.7bn.

Professor Hawkes says we should ensure that any so-called sin tax does not “make what is already quite a difficult life more expensive” for low-income households.

That means combining tax measures with others that increase equality and allow access to high quality healthy food for people of all income levels.

In this context, perhaps Johnson could have more impact on the lives of those on low incomes by looking again at his policy of slashing taxes only for the richest per cent of earners rather than presenting himself as a defender of the freedom to drink milkshakes.