Teenagers ‘drink a bathtub of cola a year’? This gimmick helps no one

As any fool knows, height is measured in double-decker buses and land is measured in football pitches. If you are measuring a very large stretch of land it should be compared to Wales, or possibly Belgium, but there is no need to be more precise than that. It is a robust system of measurement that has served Britain well for years. But how should we measure volumes of fluid?

If it is a large body of liquid, an Olympic-sized swimming pool is the proper unit. For smaller quantities, you should use the bath. Most people have a bath tub, and everybody knows it can hold a hold a lot of water, so if you want to describe a reasonably large quantity of fluid there is no need to mess around with fancy-pants jargon involving ‘pints’ and ‘litres’, you can just say ‘enough to fill a bath’.

That was the approach of Cancer Research UK (CRUK) when they informed us that ‘Teenagers drink a bathtub of sugary drinks a year’. In a press release that the BBC grandly described as a ‘study’, CRUK took data from the National Diet and Nutrition Survey and estimated how many sugary drinks are consumed by 11- to 18-year-olds. The answer, they say, is just under two-thirds of a can per day. That doesn’t sound like a great deal — and it is significantly less than they were drinking five years ago — but it is more impressive when you multiple it by 365 and put it in a bath. So that’s what they did.

Jamie Oliver has spent the last year demanding little pictures of teaspoons on fizzy drinks to inform consumers about sugar content. Now we are being asked to visualise an entire year’s supply of fizzy drinks in a bath. The temperance lobby has recently been complaining that a three-litre bottle of strong white cider ‘has the same alcohol content as 22 shots of vodka’. But alcohol is measured in units and a shot of vodka contains exactly one unit, so why not say a strong bottle of white cider contains 22 units of alcohol? Why bring vodka into it?

There is nothing wrong with putting science in a context that people can understand, but it is doubtful whether the public are better informed by such gimmicks. What is our context for a bathful of fizzy drinks? Can any of us really visualise a year’s worth of any food or drink being piled up in a bath? What lesson would it teach us if we could, other than ‘gosh, that’s a lot of food and drink’?

Such antics do not illustrate important truths, rather they obfuscate them. We already have a perfectly good measure of human energy consumption in the calorie without having to resort to cutlery and washing facilities. Obesity is about calories in and calories out. Let’s focus on that.

The story this week is that teenagers drink ‘the equivalent of 234 cans [of cola] each year’, but they don’t really. The National Diet and Nutrition Survey found that 11- to 18-year-olds consume an average of 77 grams of sugar per day. Of this, 26 per cent (20 grams) comes from sugary drinks. That is a little more than half a can of cola and amounts to 80 calories. That’s the same as you would get from eating a slice of unbuttered bread.

Does this statistic disguise the fact that some kids consume more sugary drinks than average? Undoubtedly. Would there be less obesity if the 80 calories from sugary drinks — or from an extra slice of bread — were cut out of the diet? Quite possibly. But it remains a small and dwindling fraction of the 2,000 to 3,000 calories that teenagers need. Call it a bathful if you must, but it is still a drop in the ocean.