Tuesday, 21 July 2015

Those sugar guidelines are not what they seem

At The Spectator, I discuss last week's lowering of the sugar 'allowance'. Some people have said they can't access the site if they're using Chrome so here it is in full...

Like putting Dracula in charge of a blood bank’ is how Action on Sugar’s Simon Capewell described Ian MacDonald’s role as chairman of the Scientific Advisory Committee on Nutrition (SACN) last year. Professor MacDonald’s reputation as one of Britain’s leading nutritionists gave him no protection when Channel 4’s Dispatches programme devoted half an hour to attacking any scientist who receives grant funding from the food industry. Seemingly unaware that industry-government partnerships are the norm in diet research, Action on Sugar’s Aseem Malhotra accused MacDonald of being ‘in bed with the food industry’ and called for his resignation. Similar inferences and accusations were made in a British Medical Journal ‘investigation’ earlier this year.

We shall probably never know whether this smear campaign had any influence on the conclusions of the SACN report when it was released last week, but the campaigners certainly got what they wanted when MacDonald et al halved the recommended sugar intake from 10 per cent of daily calories to five per cent. A lower limit has been the holy grail for the anti-sugar movement for years (for reasons I recently discussed). The World Health Organisation let them down earlier this year when it kept the limit at ten per cent, but SACN played ball and the talk of Dracula and blood banks was conspicuous by its absence on Friday morning.

The pool of nutritional epidemiology is murky at the best of times, leading some academics to dismiss the whole field as pseudoscience, but if you are prepared to give it the benefit of the doubt, the SACN report provides a decent summary of the evidence to date. Taken together, it does not make happy reading for the anti-sugar/low-carb movement. SACN found an association, based on ‘moderate evidence’, between sugary drinks and type 2 diabetes, but it failed to support any of the other pet theories of the anti-sugar campaigners. For example, it found ‘no association’ between sugar and type 2 diabetes, ‘no association’ between sugar and blood insulin, and ‘no association’ between sugary drinks and childhood obesity. It also found no association between fructose (the bête noire of the anti-sugar lobby) and type 2 diabetes. As for the low-carb diet, SACN found ‘no association between total carbohydrate intake and body mass index or body fatness’, nor with type 2 diabetes or cardiovascular disease. By contrast, it found ‘some evidence that an energy restricted, higher carbohydrate, lower fat diet may be an effective strategy for reducing body mass index and body weight.’

You need to reach page 183 to find the only part of the 370-page report that made the headlines. SACN explained its decision to recommend reducing sugar consumption to five per cent of daily energy as follows:

‘To quantify the dietary recommendation for sugars, advice from the Calorie Reduction Expert Group was considered. It was estimated that a 418 kJ/person/day (100kcal/person/day) reduction in energy intake of the population would address energy imbalance and lead to a moderate degree of weight loss in the majority of individuals (Calorie Reduction Expert Group, 2011) … To achieve an average reduction in energy intakes of 418 kJ (100kcal/person/day) using this estimated effect size, intake of free sugars would need to be reduced by approximately five per cent of total dietary energy (418kJ/78kJ= 5.4) … A five percentage point reduction in energy from the current dietary recommendation for sugars would mean that the population average of free sugars should not exceed five per cent of total dietary energy.’

In other words, the average person consumes too many calories and if sugar consumption was reduced from 10 per cent of energy to five per cent of energy, people would eat 100 fewer calories (unless, of course, they compensated by eating more calories from other sources). This is the sole justification in the SACN report for changing the guidance on sugar. The mathematics is correct – 100 calories is roughly five per cent of an adult’s recommended intake. The logic is not wrong, it is merely trivial. If the aim of dietary advice is to get people to eat 100 fewer calories a day, similar edicts could be announced about any ingredient or food. Telling people to eat 25 fewer grammes of cheese a day would serve exactly the same purpose, but it would not tell us how much cheese it is safe to eat.

There is no difference whatsoever between saying ‘eat 100 fewer calories’ and ‘reduce your sugar consumption from 14 teaspoons a day to 7 teaspoons’. The latter, which has now been enshrined in official guidance, is merely one way of achieving the former. It is doubtful that even one person in 100 who saw last week’s headlines realises this. It is much more likely that they think scientists have found new evidence showing that consuming more than seven teaspoons a day is inherently dangerous, even toxic.

The clear implication from the new daily ‘allowance’ is that it represents the upper limit of a risk threshold, above which it is dangerous to stray. This is not what the SACN report says, and it is not their justification for changing their guidance, but it will be portrayed as the ‘safe limit’ by pressure groups forever more.

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