It's actually worse than I thought. The new guidelines are based on a report from the Scientific Advisory on Nutrition Committee. I'd read the report before but I hadn't read the studies cited by the committee. Foolishly, I'd assumed SACN would would have fairly represented the science. In fact, not only do the studies offer no support for the arbitrary 5% guideline, many of them flatly contradict the whole sugar=poison narrative.
Here's a summary of them, in the order they are listed in the SACN report...
Drummond and Kirk (1998) advised one group of men to reduce their fat intake and another group of men to reduce both fat and sugar. After six months, the men who had only been advised to reduce fat intake had lost the most weight. The authors conclude that ‘it is surprising that many dietary guidelines recommend a reduction in sugar.’
Drummond et al. (2003) used the same methodology as above but this time neither group succeeded in reducing their fat intake. Although the men who were told to reduce their sugar intake did so, they compensated by consuming more calories from other carbohydrates and therefore did not reduce overall energy consumption.
Reid et al. (2010) gave a litre of sugary drinks to a group of overweight women every day and gave a litre of artificially-sweetened drinks to another group of overweight women. They were not told whether their drinks had sugar in them or not. Those given the sugary drinks increased their overall energy consumption in the first week but, surprisingly, energy intake then fell and within four weeks it was lower than it was when the study began – despite sugar now making up 20 per cent of these women’s daily calorie intake. This was because they reduced their consumption of fat, protein and non-sugar carbohydrates, totally offsetting the extra sugar. They did not gain weight.
Saris et al. (2000) divided 398 obese men into three groups. One group was given a diet low in fat and high in sugar while another was given a diet low in fat and high in complex carbohydrates. The third (control) group ate a normal diet. After six months, both low-fat groups had lost weight, with the high complex carbohydrate group losing the most. The authors note that ‘[i]n the search for dietary factors associated with the development of obesity, sugar intake is commonly proposed. However, epidemiological and experimental data do not support this idea.’
Aeberli et al. (2011) split their subjects into six groups and gave five of them soft drinks with varying degrees of sucrose, fructose and glucose. The control group was advised to reduce fructose intake. The researchers found that ‘total energy intake did not differ significantly between the baseline and any of the 6 interventions.’ It is not clear what relevance this has to the question SACN sought to answer.
Brynes et al. (2003) split seventeen men into four groups and gave each group different diets. Those on the high fat diet spontaneously consumed more calories, those on the high sugar diet did not.
Poppitt et al. (2002) split 39 people into three groups in the same way as Saris et al. (2000) above. Both low-fat groups lost weight, with the high complex carbohydrate group losing the most. The authors conclude: ‘A high sugar intake has been proposed as a causal factor in the etiology of obesity. The results of epidemiologic studies, however, oppose this view and are supported by our current trial. Despite a considerable increase in sugar intake, there was no evidence of weight gain in the LF-SC group.’
Njike et al. (2011) gave one group of men two cups of sugary cocoa a day and gave another group two cups of sugar-free cocoa a day. After six weeks neither group had lost weight compared to a group of men who were given a placebo, although the sugar-free cocoa ‘had a modest, favorable influence on waist circumference’. Overall sugar consumption was not measured.
Raben et al. (2002) split 41 overweight people into two groups. One group was given a very high sugar diet (28 per cent of daily energy), mostly in the form of soft drinks. The other group was given a large quantity of artificially sweetened soft drinks. Both groups were told that their supplements were artificially sweetened and they could eat whatever they wanted. Unsurprisingly, the high sugar group consumed more calories and gained weight, but the additional calorie intake was entirely due to the extra sugar. Energy intake from other food fell, partially offsetting the additional sugar calories.
Reid et al. (2007) gave half their subjects a litre of Irn-Bru a day. The other half were given Diet Irn-Bru. Specially branded bottles were marked ‘sugar’ or ‘diet’ but these were deliberately incorrect 50 per cent of the time. Subjects given the sugary drinks increased their overall energy intake, with calorie consumption rising by around half the amount of that contained in the drinks, ie. they partially offset half of the calories by reducing consumption of fat, protein and non-sugar carbohydrates. There was surprisingly little weight gain, perhaps because all the women were on a low fat diet. ‘Overall,’ the authors conclude, ‘there was no evidence that sucrose was a unique or problematic substance.’
SACN built a meta-analysis out of these studies and concluded that people shouldn't consume more than 5% of their calories from sugar, despite the fact that the studies are not comparable, most of them didn't measure sugar intake as a percentage of calorie intake and those which did measure it didn't in any way imply a five per cent limit.
It's junk science, plain and simple. Do read the whole article.
