Gene-based designer diets on way

By JENNY FORSYTH

Cholesterol level still up despite your fat-busting diet? It may just be your genes letting you down.

For years, doctors have assumed that patients whose cholesterol levels fail to drop when they are placed on a fat-reduced diet are lying about what they eat.

But now Otago University researchers studying gene nutrient reactions have confirmed that some people's cholesterol level would not drop even if they followed their diets to the letter.

For similar genetic reasons, folate levels also differ between patients.

The research, which is still in its first stages, could ultimately lead to designer diets, with patients told how their bodies will react, based on their genetic profile.

If doctors knew a patient's cholesterol would not drop simply through a low-fat diet, they could prescribe drugs as well.

But Professor Jim Mann, winner of the Bristol-Myers Squibb Foundation award, worth $1 million over five years, says patients should not race out for more fish and chips just because their cholesterol level is not dropping.

"There is more than one reason for a fat-reduced diet than to reduce cholesterol levels.

"A diet low in saturated fat can help prevent heart disease, but fat levels are also linked to obesity, which is another major health issue."

Professor Mann, who is head of Otago University's nutrition department, says researchers at the University College of London are helping to identify the genes that stop cholesterol levels dropping.

Keeping cholesterol levels low is a vital part of national health because a population's average cholesterol level is the main factor determining rates of coronary heart disease.

Scandinavian research in 1994 found that there were 30 per cent fewer deaths among those taking statins, a cholesterol-lowering drug, than among those on placebos. A 1 per cent cut in the blood cholesterol level reduces the risk of coronary disease by 2 to 3 per cent in a lifetime.

"If you took 100 people and you changed the nature of fat in their diet, the response in terms of cholesterol is so standard you can predict it with a formula," says Professor Mann.

"Within that group there will be enormous individual variation from no change to dramatic change. We used to say that the people who had no change probably didn't do what we told them, but we've now found there are some people who do exactly what we say, and their change will be very small."

Professor Mann says the research could ultimately affect the diet industry.

"If someone were to go along to Jenny Craig or Weight Watchers, it would be wonderful to be able to predict whether they would do well if they stuck to it. Having said that, you can get some idea of that already by looking at your family ...

"Maybe in 20 years' time everyone will know their genetic profile, but at the moment you can't just run off a gene programme to look for clues. It's a very complex and expensive procedure."