The prospect of a pill that can calm a disruptive child and improve intelligence has obvious appeal for parents. Those who read certain headlines this week could be forgiven for believing that such a concoction is with us. "Fish oil for every child," said the Daily Mail, declaring that "brain food supplements" of omega-3 fatty acids could soon be handed out in schools. Mark Henderson reports:
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The real story is more prosaic. The Food Standards Agency is reviewing evidence on the benefits of omega-3 fats, which some studies have suggested might improve concentration, behavioural disorders and learning. Alan Johnson, the Education Secretary, is awaiting the results "with interest". That's a fair distance from a national plan for supplements for all.
Behind this hyperbole lies some interesting science.
The way it has been misinterpreted shows the pitfalls of exaggerating the outcome of poorly designed studies and reputable but preliminary research.
Omega-3s are an important part of our diet. These fatty acids are critical to brain function and the hypothesis that eating more of them might be beneficial is physiologically plausible. So far the evidence for this is strongest in pregnancy: good research indicates cognitive advantages for babies whose mothers eat plenty of omega-3s.
The hype about these supplements, however, has emerged from studies that purport to show benefits among older children. Several schools have reported improvements on indicators ranging from exam results to behaviour. Very little of this work, however, meets standards that qualify as scientifically compelling.
Most of the research cited in support of omega-3s has lacked control groups, in which children are randomly selected to receive the real supplement or a placebo.
This makes it impossible to know whether the supplement or the belief that it might have positive effects is making the difference.
Just as importantly, few studies have been blinded. Proper trials are conducted "double blind", so that neither patient nor experimenter knows who gets the real treatment and who gets the dummy pill. This prevents doctors, or in this case teachers and psychologists, from taking a different attitude to children they know are on the supplement. When experimenters believe that a therapy will work, this influences the study group and the interpretation of data.
Double-blinding is particularly crucial when investigating traits such as behaviour, which rely on assessments that are partly subjective. When teachers know that children are getting supplements, they may treat them differently in ways that affect their conduct, or change how they categorise identical behaviour. The scope for substantial bias is obvious.
There have been five randomised, double-blind, placebo-controlled trials of omega-3s and childhood behavioural disorders that avoid these problems, and two trials found no effect at all. The largest and best, led by Alex Richardson, of Oxford University, included 117 children. Its results were intriguing; the supplements seemed almost as effective as drugs such as Ritalin for attention deficit hyperactivity disorder and deserve to be followed up. But with so small a sample size, and so few studies, it is impossible to draw definitive conclusions.
To Dr Richardson's credit, that is precisely what she has been saying throughout this past week. She is rightly concerned that over- interpreting interesting but preliminary findings makes it harder for researchers to persuade funding bodies that their work is credible science that deserves further support, and harder for parents and schools to decide whether it is worth buying expensive supplements.
Omega-3 fatty acids might indeed turn out to be cognitive enhancers that help children's educational development and behaviour, but we have to wait for the evidence.