Vegetable oil alternatives to butter may not reduce heart disease risk, according to research published in the British Medical Journal.
The study, which was carried out by the US National Institutes of Health, found that although people who avoid butter have lower cholesterol levels, they appear to be at greater risk of an early death.
The researchers, from the universities of North Carolina and Illinois, looked at data gathered in the Minnesota Coronary Experiment, where one group of hospital patients were fed a diet rich in saturated fats from milk, cheese and beef, while another group were given a higher amount of corn oil and polyunsaturated margarine instead.
The study was originally intended to show that replacing saturated fat with polyunsaturated fat from vegetable oils would protect against heart disease.
The latest analysis of the data, however, found that while there was a ‘significant reduction’ in cholesterol levels, the death rate of those on the diet increased, and that there was ‘no evidence of benefit’ to heart health.
The researchers say there has been an ‘overestimation of the benefits of replacing saturated fat with vegetable oils’.
Other researchers have come to the opposite conclusion, and say the difference in findings could be explained by the fact that many people who cut down on saturated fats eat more refined carbohydrates, which are also a risk factor for heart disease.
Nutritionists and health experts have criticised the study. Walter Willett, the chairman of the nutrition department at Harvard, said the research was ‘irrelevant to current dietary recommendations that emphasise replacing saturated fat with polyunsaturated fat’.
In Britain Dr Alison Tedstone, chief nutritionist at Public Health England, told the Daily Mail: ‘The evidence shows eating too much saturated fat raises your cholesterol levels, increasing your risk of heart disease. We are all eating too much saturated fat. This can mean too many calories leading to weight gain and obesity.’
A common way the media tends to over-simplify issues is in the vilification or glorification of a specific food substance. ‘Fat is the enemy! No wait, sugar is the enemy!’ It just isn’t that simple.
Many foods, when consumed in excessive quantities, can be harmful, but are perfectly safe when consumed sensibly. For some time the negative view of saturated fat has been challenged and we are starting to realise that things are not as simple as we once thought. This is certainly a study which forces us to question previous assumptions about fat. Perhaps its biggest limitation is that the information came from subjects who were in a nursing home or one of several inpatient mental health facilities (which potentially introduces many confounding factors), and their diet was controlled only while they were being studied in these settings. MB
Research score: 3/5