The greatest effect would be seen in urban areas with young populations, add researchers on behalf of the healthy weight campaign group.
Food Active is calling on the UK to introduce a tax on these drinks, following implementation of taxes in France, Hungary, Norway, Denmark, Samoa, Mexico, and some US states.
The study notes 30% of soft drinks consumed in the UK are diet varieties and - with aspartame stated as safe by the European Foods Safety Authority (EFSA) – asks ‘might drinks with artificial sweeteners therefore represent the lesser of two evils?’
How many soft drinks are consumed?
In the UK there has been a continuous increase in the proportion of people who are overweight or obese since the 1980s, report researchers.
The study modelled the potential impact of a 20% sugary drinks duty on local authorities in England between 2010 and 2030. Researchers synthesised data from the British National Diet and Nutrition Survey, drinks manufacturers, Office for National Statistics, and previous studies.
The National Diet and Nutrition survey estimates the average proportion of calories per day coming from sugar sweetened beverages (SSB) varied between 0.8% in men over 65 years old, to 4.9% in men aged 11-18.
People in Britain consume on average 145ml sugar sweetened drinks a day according to this survey. However, manufacturer data suggests 480mls a day – around 3 to 4 times as much. This can be attributed to wastage or under-estimation by consumers, suggest researchers.
Researchers believe a 20% duty on sugary drinks could result in approximately 2,400 fewer type 2 diabetes cases, 1,700 fewer stroke / coronary heart disease cases, 400 fewer cancer cases, and gain some 41,000 quality adjusted life years (QALYs) per year across England.
A 30% duty would result in around 3,600 fewer diabetes cases, 2,500 fewer stroke/coronary heart disease cases, 700 fewer cancer cases, and 61,000 QALYs.
“Our study suggested that a 20% duty on sugary drinks could substantially reduce the burden of diabetes, cardiovascular disease and common cancers,” wrote Brendan Collins, one of the authors, in the study. “There could be additional cash savings of approximately £15m from the reduction in healthcare costs for treating obesity related diseases.
“This is only considering the direct healthcare costs and not the human and productivity costs which would be much greater.”
Other research suggests a 20% duty would generate £276m in revenue in the UK, while a 20p per litre duty on SSBs could raise £1bn per annum.
“The national target for reduction in calories in ‘Healthy Lives, Healthy People: a call to action on obesity in England’ [a 2011 Department of Health document] is for a 100 kcal reduction per person per day, so this reduction in SSB consumption would represent 1% to 13% of this reduction,” added Collins.
Researchers acknowledge the study depends on the accuracy of the data used, and parameters such as wastage may not have been taken sufficiently into account.
The study also treated sugar calories as the same as other calories, although they point to evidence that suggests calories from SSBs may have a greater effect than other calories.
“There is a risk that a duty may have a smaller effect than anticipated because the SSB producers or vendors absorb some of the cost of the duty; this depends on the producer surplus (profit),” said Collins.
“The consumer surplus (the excess that people are willing to pay) is already factored into the price elasticity. However, in our preparatory insight work, some young people said that the price of the sugary drinks that they bought varied by so much that they were used to paying whatever price was charged.
“There is also the issue of how to address 'meal deals' and other promotions where SSBs are currently included as options in other purchases. People might also switch to bulk buying or cheaper products. However, an excise duty based on volume or amount of sugar would mitigate this effect. “
30% of soft drinks consumed in the UK are diet, but people are still concerned about artificial sweeteners, said Collins.
“There are perceptions that artificial sweeteners, in particular aspartame, are bad for health and can cause cancer, which are mainly fuelled by discredited research. In December 2013 the European Food Safety Authority clearly stated that aspartame was regarded as safe for all populations, including children and pregnant women, the only exception being individuals with phenylketonuria.
“Might drinks with artificial sweeteners therefore represent the lesser of two evils?”