Another wonder drug bites the dust. This time it's not a billion dollar pharmaceutical blockbuster like the painkiller Vioxx, but a humble food supplement. Those tubs of Omega 3 capsules can go in the bin - well, probably. A major review of the evidence in the British Medical Journal says the health benefits are not clear, but Omega 3 fatty acids, whether in oily fish or in supplements, do not prevent heart attacks or cancer.

I have to declare an interest here - I have never much liked mackerel or kippers and the thought of eel makes my stomach turn over. I also have an antipathy to swallowing any kind of pill. So my Omega 3 intake has probably been on the low side.

But I have real difficulties understanding why so many people jump with such ease and enthusiasm onto the supplements bandwagon. Yes, we all need omega 3, just as we all need vitamins A, B, C and D. But we don't need more than we get in a good diet. Eat enough fruit, vegetables, grains - and of course oily fish - and everything about our bodies will function as well as it's going to. After that, health is pretty much down to genes, smoking and drinking habits and exercise.

But there's an added temptation in the case of Omega 3. It's supposed to have an effect on the brain. Whisper the words enhanced intelligence in a middle-class household and watch mothers strip the local health food store. Add in Lord Robert Winston, everybody's favourite fertility doctor, who has been helping St Ivel advertise their Omega 3 enhanced milk, and you have a stampede on your hands.

Lord Winston justifies his cheque with the argument that children don't like oily fish. There are quite a lot of foods children don't like in my experience, but they need to get used to them - or are we happy with a diet of chips and milk, fortified with all the vitamins, minerals and Omega 3 we need?

The most interesting work with omega 3 has been the Durham study. Children from deprived backgrounds were given the supplement and their concentration appeared to improve. What does that tell you?

It may tell you that they were not eating a good diet. Omega 3 supplements may genuinely help them - but I for one would hope it was a temporary fix. What those children really need is more effort to tackle the deprivation that is the real cause of their poor diet and has profound and lasting consequences beyond inattentiveness in the classroom.