Margarine is more likely to give you a heart attack than butter, as every newspaper has told you recently. As a result of this publicity, the makers of Flora Britain's best-selling margarine have quietly changed the formula to lower the level of tran
But what no newspaper has told you is that margarine manufacturers have been aware for 23 years that the polyunsaturated fats in their products can increase the risk of cancer.
Since 1971, 20 studies have come out indicating a link between polyunsaturated fats in margarine and cooking oils and cancer. (The first appeared in The Lancet 1971; I: 464, by M.L. Pearce and S. Dayton.) Professor Raymond Kearney of Sydney University stated in 1987 that vegetable oils, rich in linoleic acid, were "potent promoters" of tumour growth.
Two studies in 1991 from the US and Canada also confirmed that linoleic acid increases the likelihood of developing breast cancer. (The American Journal of Clinical Nutrition 1991, 53: 1064S. New Scientist, 7 December, 1991: 12). Linoleic acid constitutes nearly 40 per cent of margarines high in polyunsaturates.
The recent publicity, based on research by Harvard University, centres on trans fatty acids and their likely link to an increased rate of heart attack. The acids are produced by a hydrogenation process in vegetable oils to harden them to solid fat. They are also found in fast foods such as chips and doughnuts and in the vegetable oils contained in shortenings and biscuits. They account for up to 10 per cent of the content of margarine, although the new formula from Van den Berghs, the manufacturer of Flora, is thought to reduce that to just 1.5 per cent.
Researchers at Harvard reckon that the fat could account for six per cent of all deaths from heart disease, or 30,000 deaths a year in America alone.
An epidemic of heart disease can be directly linked to the introduction of partially hydrogenated fats in food, with the first major outbreak recorded in 1920. Before the First World War, when cheese and butter were a staple of the diet, death from coronary thrombosis was rare.
Nonetheless, researchers consistently linked heart disease to animal fats, found in butter, thus giving margarine manufacturers the licence to claim their products were better for your heart.
The Harvard findings are not conclusive, however. The National Heart, Lung and Blood Institute in the US said the link between trans fatty acids and heart disease has not been proven, and goes against the findings last year of the National Cholesterol Education Program, again in the US, which reviewed the same data and concluded that "trans fatty acids do not raise blood cholesterol to the rate that saturated fat does."
!AThe Lancet, 21 May 1994; The Times, 24 May 1994 and 1 June 1994; International Herald Tribune, 19 May 1994.