Doctor, doctor - can I have a fag and a chip butty now?

RED FACES should be in abundance among the heart specialists and health charities at the moment.. After 20 years of scolding us about the risk of tobacco and cholesterol, they have got their come-uppance. The world's largest and longest study of heart disease, published a week ago, has shown that these risk factors are, apparently, irrelevant.

It was an astonishing finding and it came from an impeccable source - the World Health Organisation's "Monica" project which has compared the health records of 38 populations in 21 countries over the last two decades. Preliminary results presented at the European Congress of Cardiology in Vienna showed that heart disease rates were declining in most populations but there was no link - no link at all - with the standard risk factors of smoking, blood pressure and cholesterol.

You might have expected such a finding to provoke an outbreak of soul searching amongst the scientific establishment. Every doctor and health educator who has ever issued nannying advice to people to cut down on fags and chip butties had received a sharp reminder that causes of heart disease are far from simple. But no. The statement issued by Professor Brian Pentecost, medical director of the British Heart Foundation, said bluntly: "The unexpected findings in no way detract from the current health messages, such as stopping smoking and eating less fatty foods."

Call me old fashioned but I had always thought that the difference between medicine and witchcraft was that medicine relied on hard scientific evidence. For the medical director of Britain's leading heart charity to airily dismiss the findings of the world's largest heart study as "in no way detracting" from current health advice fair takes the breath away.

Let me stress this was no back-of-the envelope job. Indeed the British Heart Foundation itself contributed almost pounds 900,000 towards its cost. The Monica researchers studied 150,000 heart attacks and 180,000 risk factor records and the results were sent to a data centre in Helsinki for analysis. That showed that there were large differences in the rate of decline in heart disease in different centres even where they had similar trends in risk factors.

For example, in the decade from 1985-94, north Glasgow had the worst heart disease rate in the world for women and the second worst for middle- aged men (after north Karelia, Finland). Yet over the 10-year period the risk factors of smoking, blood pressure and cholesterol declined as fast in Glasgow as in any other population. Despite this fall, the heart disease rate actually rose among women and there was only a small decline among men.

Where does this leave us? If Professor Pentecost is to be believed, exactly where we were before. He said: "Heart disease is known to have many possible causes. The way in which these combine to affect over all risk is highly complex. The effect of a reduction or removal in risk factors are likely to vary across individuals." Professor Hugh Tunstall-Pedoe, one of Monica's driving forces and the director of the cardiovascular epidemiology unit at the University of Dundee, at least acknowledged that the results were "a bit of a surprise". But his efforts to explain the findings - difficulties in standardising measurements across the different countries, the long time lag before risk factors take effect - have a hollow ring to them. These problems should have been clear 20 years ago and if the researchers thought they were likely to invalidate the study why did they proceed with it?

To muddy the waters further, he offers a startling analogy to explain why no effect of smoking and cholesterol were found in the Monica study. "If you get eaten by a crocodile when you are expecting lions and tigers it does not mean that big cats have rubber teeth."

This raises more questions than it answers. All these years we have observed people carried off in their thousands by heart disease to an early death and we have assumed they were eaten by the lion of tobacco or the tiger of cholesterol when in fact many more died in the jaws of the crocodile of ...what?

Professor Tunstall-Pedoe offers no suggestions but implies that there is something out there in the jungle (a virus, perhaps?) which is more dangerous than lions or tigers but still unidentified.

L The viral theory has some backers. This would fit with the epidemic nature of heart disease in the West which rose sharply in the Sixties and Seventies and has declined in most countries since the 1980s as the Monica project has shown.

A second theory, as Professor Pentecost has suggested, is that wealth may improve survival. The Monica project showed that those countries where there was the most rapid increase in new treatments for heart disease were also those in which death rates were falling fastest. However, it was impossible to tell which treatments, if any, were most effective.

It is unclear, in other words, whether it is the quality of medical care that counts or some other factor associated with it. The countries with the best medical care tended to be the wealthiest and it may be that the material quality of life played as big a part in reducing death as the treatments themselves.

There are two lessons from the Monica study. The first is that despite decades of research and the expenditure of hundreds of millions of pounds there is still a great deal we do not understand about the fist-sized pump at the centre of our being. Yet to judge by the scientists' response to the finding you would think that it was all cut and dried. Just cut out smoking, check your blood pressure, reduce your cholesterol and you will be spared. As many people - some of them eminent heart specialists, themselves - who have led blameless lives and subsequently suffered heart disease know, it simply is not true.

The second lesson follows from the first. You cannot avoid heart disease in the way that you can avoid, say, lung cancer. If you do not smoke then the chances of your getting lung cancer are very, very small. But you may still succumb to heart disease even if you avoid smoking, drink a glass or two of claret, bicycle to work and follow all the other advice issued over the past two decades. It is clearly wise to heed the findings of earlier studies and steer clear of the lions and tigers but scientists do us a disservice if they fail to warn us that crocodiles may be about, too.