Doubts were cast on the link between diet and cholesterol yesterday by Prof James McCormick of the Department of Community Medicine in Trinity College Dublin.
In his address to doctors, Prof McCormick said cholesterol "may not be the villain" in causing heart attacks. He said the link might not be as straightforward as they currently believed.
He spoke of the "difficulties and dangers of the ascription of cause" and the "fallacy of association", particularly in relation to coronary heart disease.
There was huge enthusiasm among the medical profession for lowering cholesterol, but Prof McCormick pointed out that cholesterol occurs naturally in people. "You may make a lot of it or not." There is an association between high cholesterol and heart disease, but cholesterol may simply be an indicator of some other abnormality of a person's fat breakdown.
Recently, he said, new studies with a group of drugs called statins showed for the first time a drug for lowering cholesterol that worked as well for people with high and low levels of cholesterol, perhaps working on some other factor not directly related to cholesterol.
Explaining his theory, Dr McCormick said there was acknowledged to be a link between smoking and cervical cancer.
"But the problem is that people who smoke cigarettes are not the same people as those who do not. It may be cigarette-smoking; it may be something else. Maybe people who smoke are more likely to get drunk, to have casual sex. Maybe there are other factors."
By the same token, he said, there may be unknown factors associated with cholesterol levels. Doctors, he said, do not know nearly enough. "It is a medical hubris." There was a belief that doctors knew a great deal which had led to medicine getting the status of religion. "Religion used to explain birth, death and the pain of the journey in between; now medicine is supposed to explain that."
In a session about "lying in practice", Prof McCormick said doctors had a problem being honest. "If you are honest you have to know what the truth is," he said, adding that doctors very often did not know.
Dishonesty ranges from outright lies, to unduly optimistic prognoses. It also includes exaggerating or diminishing the risk of actions in order to encourage compliance "with what we feel is in the patient's best interests".
Prof McCormick questioned whether "limited paternalism" was ethically justifiable. "I would guess that all of us from time to time have been unduly optimistic or less than fully honest in the best interests of the patient."
This, he said, was paternalistic, which was now unfashionable, but there were occasions when the doctor had to decide "in the best interests of the patient".
"If someone comes in with a tingling in the arm I might think it was MS. I would not say that at that stage," he said, adding that if he was asked he would tell the patient "but not at that moment" until further tests were carried out.