A tad hard to swallow

Are omega-3 fatty acids really vital for our health? Over the past few years, we've read of the fantastic benefits of omega-3s, found in fish oils.

Recently, scientists reported that women who take fish-oil supplements reduce their risk of breast cancer by a third.

But while experts agree omega-3 pills can cut the risk of heart disease and are vital for brain development in the womb, opinion is divided over other benefits.

Tom Sanders, professor of nutrition and dietetics at Kings College London, and Professor Amanda Kirby, specialist in developmental disorders at the University of Wales, have dismissed many of the benefits of omega-3 pills.

However, according to neuroscientists and nutritionists, Britons' health is at risk as they aren't getting enough omega-3 from fish.

"There's an epidemic of brain and mental disorders in the UK, such as ADHD, depression and cerebral palsy," says Professor Michael Crawford of the Institute of Brain Chemistry at London Metropolitan University. "The evidence shows that the lack of omega-3 from fish in our diet is the main factor."

This clash of scientific opinion makes things confusing — do we need fish-oil pills or not? Take a look at the evidence to help you make the right choice.

Why do some experts dismiss fish-oil pills?

The reputation of omega-3s as a panacea has made them a popular supplement.

Found naturally in oily fish, such as mackerel and sardines, they are added to many foods, from eggs to orange juice, while capsules are found on chemists' shelves.

According to the Food Standards Agency (FSA), UK, say you can get enough from eating oily fish. But not everyone likes oily fish, so millions have taken omega-3 in a pill form.

Professor Sanders says we're wasting our money. The results of recent trials testing the benefits of fish-oil pills on the brain found them no better than a placebo.

A trial of 450 school pupils by Professor Kirby found no difference in reading, spelling or handwriting between those who got fish oil for a year and those on a placebo.

Another trial failed to show that fish-oil supplements kept elderly patients' minds sharp.

Other studies have proved equally disappointing. The results of a review of research into the benefits of omega-3s on children with ADHD were too inconsistent to draw any conclusions. A review of the effects on depression and mental health problems found no benefit.

Professor Crawford disputes this. Since the Seventies, he believed the rise in heart disease was down to lack of omega-3s.

"I predicted that a lack of good fats was going to eventually show up as damage to the brain. That is what is happening."

But haven't studies shown that omega-3 supplements don't boost mental performance?

"If you want to have a big impact on the brain, the crucial time is just before and after birth," Crawford says.

He dismisses the trial that found no effect on primary-school pupils.

"The benefit was measured in a wishy-washy manner," he says.

Robert McNamara, associate professor of psychiatry at the University of Cincinnati College of Medicine, gave 10-year-old boys a dose of either 1.2 grams of omega-3 fatty acids or a placebo every day for eight weeks.

Later, when he scanned their brains while they were doing a task requiring them to focus, he found the areas needed for attention were more active in those who had the fish oil but not the placebo.

Omega-3 supplements might also benefit adults at a risk of developing a psychotic disorder, a study published in the Archives Of General Psychiatry found.

Only 5 per cent of the patients who took 1.2 grams of omega-3 supplements daily became seriously mentally ill later, while more than a quarter of those in the placebo group progressed to severe psychosis.

So what are fish oils good for?

Even sceptics agree that some of the claims for fish oil have good evidence to back them up. The strongest of these is that omega-3s cut the risk of heart disease if you have had a heart attack.

It's also not disputed that fish oil is essential for unborn babies' brains. Evidence that it reduces pain and inflammation if you have arthritis is also strong.

The jury is out on other claims. Omega-3 supplements have been tried as a treatment for asthma but with limited success.

Results are better for macular degeneration, which damages the centre of the eye and can lead to blindness. In 2006, a study of more than 3,500 patients found those eating the most fish cut their risk of developing the disease in half.

How much fish oil do we need?

The FSA recommends eating two portions — or 240 grams — of fish a week, one of which should be oily.

But in Britain people eat an average of just 50 grams of fish a week, so this is an optimistic target.

But even that target might be too low. "There is no scientific basis for this amount," says Professor Jack Winkler, former director of the Nutrition Policy Unit at London Metropolitan University.

"This is only what the FSA thinks might be a minimal and achievable goal — not the amount for maximum nutritional benefit.

So should we be taking supplements?

Not according to the FSA. It says the evidence for supplements isn't strong enough.

However, even if people aren't eating enough fish to supply omega-3 fatty acids, we can make enough of the type of omega-3 found in fish (DHA) from a plant version (ALA), found in nuts, seeds, broccoli and leafy vegetables.

"Vegetarians, who generally have very low levels of DHA in their diet, also have low levels of heart disease," Professor Sanders says.

"We have a natural capacity for converting the ALA omega-3 found in plants into the DHA form found in fish," he adds.

But not everyone agrees.

Last year, Thomas Brenna, a professor of nutrition and biology at Cornell University, New York, produced a review of the evidence and concluded that most people could only convert less than 1 per cent of the plant version into DHA. Two years earlier, a Canadian review had come to the same conclusion.

That's not enough to get the equivalent of two to four fish a week.

Professor Sanders disagrees. "If you measure how much people convert when they're healthy, it will be small. But when the body needs DHA, it ramps up the conversion rate. And we have examined young girls with atrocious diets but their DHA levels are normal," he adds.

Who should take pills?

Experts agree that supplements can be taken by anyone who has had a heart attack.

It is advisable to get 7 grams of omega-3 from fish a week, which means eating four portions.

If they can't get that they can take a supplement of 1 gram a day.

However, other official bodies have put the amount needed to reduce heart disease risk at more than that.