Friday, November 03, 2006

Trans fat

Health officials in New York are planning to prohibit the city’s restaurants from serving food with more than a minute amount of partially-hydrogenated fat, or trans fat. This is based on research which suggests that these fats, frequently used in cooking oils and baked goods like cakes, biscuits and doughnuts, can have a negative effect on cholesterol levels while not having any particular nutritional value other than calories. Trans fats seem to raise levels of ‘bad’ LDL cholesterol, in much the same way as saturated fat, but also seem to lower levels of ‘good’ HDL cholesterol. Dr Walter Willett from Harvard University has estimated that if artificially-produced trans fats were removed from the American diet, up to 228,000 heart attacks could be prevented each year.

There are many ingredients in our diet which add little to the nutritional value of food but which are added to improve the flavour, texture or other qualities: including sugar, salt (beyond the relatively small amount we need to survive), spices, oils, butter and so forth. Trans fat falls into this category, improving the texture of certain foods while being more stable than many of the alternatives. If we are going to ban it, we should make sure we're doing it for a good reason.

The problem is that the claims made about this 'artery-clogging' fat seem out of all proportion to reality. It certainly appears to be the case that eating more trans fat and saturated fat increases cholesterol levels – but the link between cholesterol and heart disease is a lot more tenuous than we're usually led to believe. In fact, as Malcolm Kendrick points out elsewhere on spiked, 'no clinical trial on reducing saturated fat intake has ever shown a reduction in heart disease'.

The link between trans fat and heart disease seems to be equally weak. As Steven Milloy has pointed out on his website, most of the studies done seem to be produce results which are not statistically significant or the association is weak. It is certainly not the kind of data that would justify the removal of a useful food product from restaurants as New York's health officials propose – and makes a mockery of Willett's figures on heart attacks. The irony is that when saturated fat became dietary public enemy number one thirty years ago, one of the alternatives widely suggested was trans fat.

We should stop listening to those health campaigners who have made a career out of scaring us about our food. Trans fat is highly unlikely to shorten our lives, but scare stories like this one will certainly make them more miserable.

Fear of margarine: the trans fat myth, Junkscience

The Great Cholesterol Myth, by Malcolm Kendrick