How do we know the UK’s sugar tax is working?

The soft drinks industry levy came into effect in the UK in early 2018. The first study to investigate the effect of this “sugar tax” on individual-level consumption has just been published in the Journal of Epidemiology and Community Health . The headline finding is that adults reduced their daily added sugar intake by about two and a half teaspoons.

Using data from the annual National Diet and Nutrition Survey, the study summarised the amount of “free sugar” in people’s diets between 2008 and 2019. (Free sugar is added sugar – the sugar contained in honey, syrup and fruit juices.) The data included dietary information from almost 8,000 adults, who reported on all foods they consumed over four days using food diaries.

The findings suggest that a year after the sugar tax was introduced, adults reduced their daily free sugar intake by about 10.9g, and a reduction in soft drinks accounted for over half of this reduction. This translates to a reduction of around 40 calories daily, which if maintained, and assuming no other changes, could lead to 1.

5kg weight loss over a year. While this sounds impressive, it is important to remember that the study relied on self-reported measures of dietary intake and sugary drinks. It is well known that people often under-report their food intake, particularly foods that are perceived as unhealthy, such as those that are high in sugar.

The study tried to account for this by also looking at changes in dietary protein intake over the .