Nano Girl Michelle Dickinson: Keep an eye on UK sugar tax

Research shows that just one can of soda a day can increase your risk of dying from heart disease by almost one third.

This week, the UK announced its war against sugary drinks with a 25p (53c) a litre tax on soda. Based on the science available, should we follow suit?

At more than 85 million litres consumed a year, New Zealanders love their fizzy drinks. Easily accessible in supermarkets, cafes, fast-food chains and dairies, and offered in child-attractive bright colours at affordable prices, it's easy to see how we rank 9th out of 18 developed countries for soft drinks consumption.

Making up 24 to 28 per cent of the total sugar consumed by 5- to 18-year-olds, a large proportion of our young population's sugar intake is from fizzy drinks. With one litre of cola containing around 27 teaspoons of sugar, it's easy to see how almost one-fifth of the total sugar intake of New Zealand adults comes from non-alcoholic beverages.

What are the risks associated with drinking so much sugar? A 2012 study in the American Journal of Clinical Nutrition shows that it leads us to consume more calories than we realise, which can lead to weight gain.

Reading labels on the back of many food items at the supermarket will show high sugar levels in processed foods - not just soft drinks - including a simple can of baked beans. The big difference is that beans, unlike soda, contain fibre and so require chewing, which initiates a series of digestive reactions in your body, slowing down the release of the sugar in your bloodstream and causing you to feel fuller faster.

Several studies show statistically significant evidence of increased weight gain from soft drink consumption. Fizzy drinks have been identified as one of the most significant contributors to obesity and other associated health issues such as type-II diabetes, cardiovascular disease and dental cavities. Research shows that just one can of soda a day can increase your risk of dying from heart disease by almost one third, and your risk of developing type-II diabetes by more than 25 per cent.

The 2015 World Health Organisation guidelines suggest that "free sugars", including those found in fizzy drinks as well as any sucrose, glucose, honey, syrups and fruit juices, should make up less than 10 per cent of our daily energy intake. The average adult consumes 2000 calories a day, so that equates to 53g, 13 teaspoons or just one 500ml bottle of cola a day total sugar consumption.

There is a strong case for reducing our intake of soft drinks, and monitoring our sugar intake overall. The next question is whether or not a tax as imposed by the UK Government is an effective mechanism to drive this change. It will be interesting to watch the data in the UK as the policy takes effect.

Countries that have tried it to date, including Mexico and Denmark, have seen only small reductions in sugary drink consumption.

Proponents of the tax argue that the increased tax revenue collected could be invested in sports or nutrition education programmes, and that a sugar tax would entice manufacturers to produce alternative cost-competitive products by reducing cheap sugar fillers or shifting to sweetening with natural plant-based sweeteners. As yet, there is insufficient evidence to draw a conclusion in my view.

From the data we have to date, a sugar tax is unlikely to be the silver bullet that solves New Zealand's growing obesity troubles. I think we need to monitor what happens in the UK closely, and consider what actions we can take - education, supply control, labelling, taxation and other options open to us - to improve our statistics. Thirty-five per cent of New Zealand adults and 22 per cent of children are overweight. We should not be one of the top three fattest countries in the world.

Dr Michelle Dickinson, also known as Nanogirl, is an Auckland University nanotechnologist who is passionate about getting Kiwis hooked on science. Tweet her your science questions @medickinson