The researchers from the British Heart Foundation Health Promotion Research Group at the University of Oxford and the Centre for Food Security at the University of Reading have published their findings in the British Medical Journal.
A typical sugary drink can contain six to 15 teaspoons of sugar
A tax on sugary drinks has been proposed as a public health measure for a number of reasons. Sugary drinks (soft drinks with added sugar such as fizzy drinks, squashes and cordials) have been shown to increase the risk of obesity, diabetes, cardiovascular disease and tooth decay. They only suppress appetite weakly, so consuming fewer sugary drinks is unlikely to result in an increased intake of other sources of calories. There are no beneficial nutrients in sugary drinks, so reducing consumption will not remove important nutrients from the diet. And from a legislative perspective, sugary drinks can be clearly defined, the researchers say.
The scientists used a large survey of shopping preferences of families in the UK to estimate how purchases of sugary drinks would change in response to a 20% increase in their price.
They also looked at how purchases of other drinks, such as orange juice, milk and diet drinks, might change in response to the price change. They then used this information to estimate the change in average calorie intake and obesity
The research suggests that purchases of sugary drinks would reduce by around 15% with people mainly switching to diet drinks and tea and coffee. The expected reduction in energy intake is 28 calories per person per week.
The researchers estimate this would reduce the number of obese adults across the population by 180,000 (with the number likely to be in a range from 110,000 to 250,000), or 1.3% of all obese adults in the UK.
The impact on obesity is likely to be much greater in younger adults who drink larger quantities of sugary drinks than older adults. On average, people aged 16-29 years drink around 300ml of sugary drinks per day, compared to just 60ml in those aged over 50.
The Oxford and Reading research team also investigated the effect on obesity among different income groups. The study indicates that there would be similar health gains across all groups, looking at the thirds of the population with lowest, middle and highest incomes.
The estimated increase in the amount people would spend on drinks would be an extra 9p a week (or under £5 a year) for those in the lowest income group. It would be 6p per week for those in the highest income group. The increase in expense is small as most people would react to the tax by purchasing fewer sugary drinks, the study suggests.
Dr Adam Briggs of the British Heart Foundation Health Promotion Research Group at Oxford University, and joint first author of the study, says: ‘Sugar sweetened drinks are known to be bad for health and our research indicates that a 20% tax could result in a meaningful reduction in the number of obese adults in the UK. Such a tax is not going to solve obesity by itself, but we have shown it could be an effective public health measure and should be considered alongside other measures to tackle obesity in the UK.’
Dr Oliver Mytton of Oxford University, and the other joint first author, says: ‘Younger adults and children consume much greater quantities of sugary drinks. This is a concern for their health, not only in terms of diabetes and obesity, but also tooth decay. Our work suggests that a sugary drinks tax would have a much greater impact, in terms of reducing obesity, in younger adults.’
Dr Mike Rayner, head of the British Heart Foundation Health Promotion Research Group at Oxford University, says: ‘Taxes on sugary drinks are moving up the political agenda in the UK and abroad. Increasingly, governments are recognising the health burden imposed by sugary drinks and that this burden can be reduced by measures to discourage consumption. Because sugary drinks do not provide any beneficial nutrition there are no downsides to reducing consumption levels in the UK using taxation.’
Professor Richard Tiffin of the University of Reading says: ‘Obesity is a ticking time bomb. Doing nothing risks condemning millions of people to poor health and an early grave. This is a complex battle in which a soft drinks tax could be a useful weapon, but on its own would not go far enough in the face of such a massive problem. Sedentary lifestyles, poor education, addiction to alcohol and tobacco, and poverty all play far more significant roles than fizzy drinks in causing bad health.
‘Taxing food is a big step, especially when spiralling bills are already making households poorer, and will make very little difference if people are unable or unwilling to make healthier choices elsewhere in their lives.’
A 20% tax would put around 12p on a 330ml can of fizzy drink bought in a supermarket or about 40p on a 2L bottle. A typical sugary drink can contain six to 15 teaspoons of sugar.