Monday, October 27, 2008


Many people believe that sugar (sucrose) intake causes behavioural problems. The two most common specific beliefs are that eating sugar causes worsened hyperactivity; or that eating sugar causes a rush of energy, followed by a plunge into fatigue as the sugar level "crashes".

In fact there have been a lot of very good studies looking at this, and the evidence is quite clear that sugar does not cause hyperactivity. There is an association between high sugar intake and antisocial behaviour, but the relationship is probably not causal. It is much more plausible that those with more antisocial behaviour in the first place happen to choose to consume more sugar.

In some of the prospective, randomized studies, in fact, individuals consuming sugar (instead of a placebo) did better, particularly in terms of learning tasks.

The evidence is also very clear that so-called "reactive hypoglycemia" is very rare, even in people who insist that they have it. However, there may be some individuals who become more irritable as their blood glucose level drops, even if the drop is not down to clinically hypoglycemic levels.

There is evidence that some individuals may respond adversely, in terms of their behaviour, to certain foods, but actually sugar is not a common such food, according to well-controlled studies.

I do affirm that moderating sugar intake, and also eating meals with a lower glycemic index, is part of overall good long-term health.

But most of the claims about sugar influencing behaviour adversely are part of a myth, not supported by clear evidence.

For an excellent review of the evidence on this matter, see this article by David Benton (May 2008):

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