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Miracle superfood or just a fishy snake oil?

IT'S A CURE for what ails you, say its fans -- and those who make supplements: omega-3, the oily fish-derived superfood.

The original Mr Dim But Nice, Bertie Wooster, put his butler Jeeves's keen intelligence and bulging forehead down to the amount of omega-3-rich fish he ate.

And if (presumably fish-eating) scientists are to be believed, it's all true. Omega 3, in some of the thousands of studies done on the fashionable wonder food in recent years, can help everything from psychosis to diabetes.

Melbourne University psychiatrist Paul Amminger gave fish-oil tablets for three months to 41 people thought to be at risk of developing schizophrenia, and 35 others received a placebo.

Only two of the fish-oil group had developed a psychotic disorder a year later, while 11 of the placebo group fell ill, reported the study published in the Archives of General Psychiatry.

And research in Aylesbury Jail by Professor John Stein of Oxford University, brainy brother of chef Rick Stein, found violent offences dropped 37pc when the prison diet was made high in multivitamins, minerals and essential fatty acids. In other words, your classic greens, grains and fish.

A 2007 study by Jill Norris, published in the Journal of the American Medical Association, found that children with a family risk of diabetes were 55pc less likely to develop the disease if they ate a diet rich in omega-3.

Joseph Hibbelin, who led research on omega-3's effects in lowering aggression for the US National Institutes of Health, says modern diets are simply deficient.

Hibbelin was also involved with Brian Hallahan, from Beaumont Hospital, in an experiment on using omega-3 on patients who repeatedly self-harmed.

They were reportedly just as impulsive and aggressive after three months -- but their depression, suicidal feelings and stress had improved significantly.

Hibbelin points out that if you eat a lot of omega-6 (another fatty acid, found in deep fries, ready meals, snacks and margarine) it edges out the good omega-3.

Hibbelin matched the rise in omega-6 consumption in 38 countries with rising murder rates. But in societies with high omega-3 consumption -- Japan, for instance -- he said there are low rates of murder and depression.

Wait a minute, though. Don't the Japanese have a massive suicide rate? And didn't they get a bit rough in Nanking and Burma in the 20th century, when they were eating just as much fish?

Not all supplements containing the magic omega-3 are the same. Nutritionist Alex Richardson told a newspaper making comparisons that Barlean's Omega Swirl is high in omega-3, but some other supplements aren't all that. Vegetarians should look for omega-3 pills made from algae.

Even dogs will have their day -- pet food multinational Dechra is about to launch an omega-3 enriched food, Specific, in Ireland.