New Scientists - Mexico’s sugary-drink tax was all fizz for very little pop

A much-heralded tax on sugary drinks in Mexico has had only a modest impact and shows much more is needed to turn the tide of obesity, says Tom Sanders, emeritus professor of nutrition and dietetics Mexico's sugary-drink tax was all fizz for very little pop

Mexico has been a much-vaunted testing ground for a nationwide tax on unhealthy sugar-sweetened drinks. Its consumption of these is among the highest in the world, so in 2014 the government decided to act and introduced a 10 per cent levy.

Health campaigners around the world have championed this experiment. In the UK, for example, calls to follow suithave been growing, backed by supporters such as celebrity chef Jamie Oliver. Now the first robust evidence on the impact of Mexico’s tax is in, and the gains look very slender.

A soda tax sounds like a good idea. Soft drinks are the main contributor to high intakes of free sugars, which include those added to food plus sugars found naturally in fruit juice, honey and syrup. A 330-millilitre can of full-sugar fizzy drink contains the equivalent of 9 sugar cubes.

We also know the replacement of sugar-sweetened drinks with water or non-caloric alternatives reduces weight gain, especially in children. High consumers of sugar-sweetened beverages are at increased risk of developing diabetes and cardiovascular disease.

In October, Public Health England, acting on advice from the UK government’s Scientific Advisory Committee on Nutrition, recommended free sugars contribute no more than 5 per cent of daily energy intake (equivalent to six or seven cubes). Current daily intakes in UK adults and teenagers are equivalent to 15 and 18 cubes respectively.

Then in November, the UK parliamentary Health Select Committee supported a proposal for a tax on sugary drinks following campaigning by 60 health organisations as well as Oliver.

At the time, evidence that this would reduce consumption and make a meaningful contribution to calorie reduction was scant. Modelling studies for Public Health England based on a 10 per cent price increase suggested a fall of 7.5 ml per day, which supplies less than 1 gram of sugar or about 3 kilocalories. Yet the select committee was told that the tax had been a success in Mexico.

However, evidence of its impact there, just published in the BMJ, is underwhelming. Purchases of taxed sugar-containing beverages fell by 12 ml per head per day and those of untaxed beverages (including fruit juice) increased by 36 ml/head/day.

The fall in taxed beverages was greater in the poorest households, at 35 ml/head/day, but even this is only equivalent to about 1 sugar cube (16 kcal) – a drop in the caloric ocean.

In addition, a sugar tax is likely to have a greater impact in Mexico than countries such as the UK, because Mexicans spend a greater proportion of their income on food and drink so a levy should bite more deeply.

Another problem is that while the soda tax debate has increased awareness of the hazards of consuming a lot of sugary drinks, it has detracted from nudging people to eat less and select a balanced diet.

The dental epidemiologist Aubrey Sheiham used the term “sweet nothing” to describe government inaction on cutting sugar intake. He was talking about tooth decay, a problem largely solvable with good oral hygiene and fluoride.

The UK government may well decide to do sweet nothing about sugary drinks, but the problem of reining in consumption of sugar as part of a wider strategy to curb obesity and diabetes remains urgent and unsolved.