RUNNING TO FAT

Press, 25 July 1984, Page 21

RUNNING TO FAT

JAMES LE FANU,

doctor and medical writer for

the London “Observer,” says we can relax —for the great majority of us, meat, butter and cream are perfectly safe.

The idea that eating less fat helps prevent heart disease has, by now, become a truism. What is lacking, however, is any real evidence that it is actually true. On the contrary, over the last 10 years the largest and most expensive medical experiment ever mounted has suggested that for the great majority of the population, eating fat makes no difference whatever. The theory which has dominated dietary thinking for so long is called the Diet-Heart hypothesis, and it involves the notorious scare word — cholesterol. The theory says that if you eat too much saturated fat, the kind found in meat and dairy products, then your body will in turn produce too much cholesterol, which is one of the fats made by the liver. The cholesterol, it is supposed, then accumulates and literally clogs up your arteries, making you more Gable to suffer heart disease. The whole idea began with the work of an American scientist called Ancel Keys, who examined the rates of heart disease in seven different countries during the 19505. He found two extremes in Japan and the U.S.A. Japan had a low rate of heart disease and the people Keys examined had a low consumption of saturated fats and a low level of cholesterol in the blood. By contrast, Americans ate more saturated fat, their cholesterol level was higher and they were more liable to heart disease. Keys’s discovery pointed the same way as another observation: around 5 per cent of the population has, often for genetic reasons, a high level of cholesterol in the blood, and these people also have a high rate of heart disease. It looks Gke an open and shut case, until the evidence is examined more closely. For example, Keys’s Japanese were 500 fishermen from a village in the north of the country and his Americans were 2,500 railway workers — two groups which have far more differences between them than what they eat. Indeed, the early studies only suggested that the more primitive a society, the less likely its people were to have heart problems. When two more similar countries, Scotland and Sweden, were

compared there was a five-fold difference in heart disease, though cholesterol levels were much the same. However, the weight of circumstantial evidence was enough to encourage many expert committees to recommend that if people wanted to avoid heart disease, they should cut down the amount of meat and dairy products they ate. But the proof was still missing. That could only come by testing the hypothesis over a number of years through reducing the amount of fat in the diet of middle-aged men and watching the rate of heart disease fall. So at the beginning of the 1970 s a series of “mass intervention” trials was organised. Over the years these involved over 60,000 men — the sex which has much the worse rate of heart disease. Together, they cost more than £lOO miUion. The biggest involved 48,000 men in five European countries and was conducted by the World Health Organisation. It reported last year. Another, with 12,000 American men, was called the Multiple Risk Factor Intervention Trial, snappily titled “Mr Fit.” It reported in 1982. The year before that a much smaller Norwegian study was published. In each trial the participants were divided into an “intervention” and a “control” group. The “intervention” men were encouraged to reduce the amount of fat in their diet by adopting new shopping, cooking and eating patterns and to stop smoking with assistance of hypnosis and aversion therapy. The control group received none of these attentions.

When the final report was published last year, it became clear that the Diet-Heart hypothesis was in big trouble. In the two largest trials there was absolutely no difference in the rate of heart disease or in the total number of

deaths. In the small Oslo trial of 1,200 men, though there was no difference in the over-all number of deaths, there was indeed less heart disease in the intervention group. But this result cannot be used to justify advising everyone to change their diet. AH the participants were drawn from that small group of 5 per cent of people in the West who have a high level of cholesterol in their blood in the first place, and so their experience is not relevant to the healthy majority. Even more important, the diet these Norwegians had to adopt in order to lower their blood cholesterol was so drastic as to be impractical as a general recommendation. It wasn’t simply a matter of substituting margarine for butter, but of having none at all, or the merest smear of margarine on bread. In their sandwiches there was to be no salami, ham, beef or egg, but fish or a vegetable filling. All meat was severely restricted; only low fat cheese was permitted, and there was certainly no cake, pastry or puddings. There is a great deal of saturated fat in the diet of all of us — around 40 per cent of our total calorie intake. To bring that figure down to the 30 per cent recommended by some doctors would mean the most massive changes in our eating habits, as the doubtless deprived Norwegians discovered. The fact is that the body’s homeostatic mechanisms are so powerfully designed to maintain constant levels of cholesterol in the blood that only fundamental changes in diet would make any difference. So, although doctors will advise their few patients with naturally high levels of blood cholesterol to adopt a low-fat diet, the difficulty in sticking to one which has any significant effect almost invariably means that they win need to be prescribed choles-

terol-lowering drugs as weH — or else have a normal diet and rely entirely on the drugs, Apologists for the hypothesis have attempted to explain away the results of aH these tests, by saying that the methods used were faulty. But as Michael Ofiver, Professor of Cardiology at Edinburgh University wrote in the “Lancet” last yean “The fact is that intervention appfied on a mass scale has not been shown to be of benefit against heart disease. It is no good saying that it might have been so had the circumstances of the testing been different, or that it might be so in the future.” Interestingly, while these very expensive trials were showing that dietary change can have no useful impact on heart disease, a natural experiment that costs nothing was pointing to the same conclusion. The incidence of heart disease in the U.S. has decbned by nearly a quarter over the last 15 years — across all ages, races, classes and in both sexes. Nobody is sure why, but to have been even partly attributable to diet-induced changes in blood cholesterol level would have required a revolutionary and uniform change in American eating habits. And that has simply not happened. The most recent report to endorse the low-fat diet as a means of preventing heart disease was published in Britain last year by the National Advisory Committee on Nutritional Education — N.A.C.N.E. This attracted a lot of controversy, especially because of allegations that the food industry, had contrived to suppress it. The N.A.C.N.E. report said, quite correctly, that expert committees “show a strong consensus of opinion that heart disease can be prevented by the reduction of total fat in the diet.” But since these committees all made their recommendations before the trial results were published, the expert evidence is simply out of date. Astonishingly, N.A.C.N.E. fails to mention the intervention trials at all. The lessons of the trials are that a reduction in fat intake may be of benefit to a small group of men — the unfortunate 5 per cent with

naturally high cholesterol levels — but they will almost certainly have to take cholesterol-lowering medication as well. For the rest of the population, it appears that fat reduction is both impractical and irrelevant.

The clue to why N.A.C.N.E. and other experts ignored the crucial evidence of the trials probably Ges in their professional role. Many are involved in the field of community health and are concerned with the prevention of disease rather than its treatment. Much disease is indeed preventable, but in their enthusiasm to expand their influence they have dodged the reaGty

of the hard scientific evidence. As Dr PhiGp Payne, head of the Department of Human Nutrition at the London School of Hygiene, says: “There is just as much danger of being manipulated by health professionals as by any other group who provide a service. Unless they justify their role, they wiU have no jobs, careers or money.” For their enthusiasm has had mischievous consequences, not least the fact that many healthy people have been bulbed into changing their diet, wrongly believing this will help prevent then- suffering disease in the future. It is also a threat to the reputa-

tion of the whole medical profession. J. R. MitcheG, Professor of Medicine at Nottingham University, noted when he recently reviewed and dismissed the claim that fat causes heart disease: “Over the centuries the pubbc has been given so many crazy admonitions by “leaders” of medical opinion that they cannot decide who to listen to or what they should do. If we fail in our duty to differentiate between what is known and has been proved and what is merely believed, then the harm from such false advice is to our credibility and to our self-esteem as scientists. The greatest of all foGies is to

bebeve passionately the palpably-not-true.’’ There are a few prosaic certainties about diet and illness. If you eat too much you will get fat, and that is bad for you. If you eat too many strawberries you might get a stomach ache. Some people find that their acne improves if they cut out chocolate. A good intake of fibre helps regular bowel function. But for healthy people there is no need to make changes in what they eat. This message might not make good television or sell many books, but it does have the outstanding virtue of reflecting proved scientific knowledge.