Those who grew up in the Seventies will remember campaigns portraying butter as a nutritional villain and margarine as a saint. But last month, a study in the British Medical Journal revealed that while those who avoided butter in favour of healthy vegetable oil spreads saw their cholesterol levels drop, the result didn't translate to a lower risk of heart disease or premature death.
Indeed, butter has come back into vogue in recent years and market analysts Mintel says sales are growing by four per cent a year. Does this mean lashings of the stuff - along with other forms of saturated fat, such as ghee, lard and meat dripping - are back on the menu?
The study, a reappraisal of data from a randomised controlled trial from 1968 to 1973, looked at 9,570 participants who replaced saturated fat in their diets with vegetable oil, which is rich in linoleic acid, a polyunsaturated fat. While the vegetable oil group saw cholesterol levels drop by 13.8 per cent, it failed to have the same effect on their risk of death; in fact, they actually had a higher risk than those who consumed the butter.
Though critics attacked the study for using old data and failing to take into account other risk factors for heart disease, it adds to a growing body of evidence questioning what we think we know about saturated fat. The Scientific Advisory Committee on Nutrition is rethinking its guidelines and is due to report back in 2017.
Current advice has it that our saturated fat intake should be no more than 11 per cent of our diet. That amounts to about 20g a day for women (equivalent to a buttered croissant for breakfast, and meat bolognese for dinner) and 30g for men (a grilled beefburger, and a bacon, egg and cheese sandwich).
But even Public Health England (PHE) concedes that it is time for a rethink on these recommendations. "There have been several papers suggesting the current guidelines are not correct," says Dr Louis Levy, chief nutritionist at PHE. "Having said that, Britons are still eating about 12.5 per cent of their diets from saturated fat, and that's worrying."
In response to the British Medical Journal study, Caroline Jary, director of Unilever spreads in the UK, said: "Overwhelming evidence from the past five decades confirms that reducing intake of animal fats such as from bacon and butter and replacing them with oils and fats from plants, like those found in our spreads, contributes significantly to heart health."
The dark side of cutting out all fat?
Trying to eliminate fats from our diets has led us to replace even healthy fats with sugars and other simple carbohydrates that may be worse for us, says Dr Nita Forouhi, from the Medical Research Council's epidemiology unit at Cambridge University, who has studied the role of fats and disease for more than 20 years.
"Supermarkets have hundreds of products that are low fat, but for added taste and palatability contain refined carbohydrates, mostly sugar," she says.
Saturated fats, says Dr Forouhi, are not the villains previously thought. One extensive study from McMaster University in Canada last August found no evidence that eating higher amounts of saturated fat raised the risk of death - but it did find that eating more trans-fats was linked to increased risk of death and heart disease.
"The real villains in our current understanding of risk of obesity, heart disease and type 2 diabetes are the industrially produced trans-fats," says Dr Forouhi.
Since most artificially produced trans-fats have been removed from foods that used to contain them, such as commercial margarines, intake in the UK has fallen to about 0.7 per cent of our diets, well below the recommended limit of two per cent.
Look for the word "hydrogenated" on the label, says Dr Levy, which means the oil has been treated with hydrogen and pressure to harden it, a process that creates trans-fatty acids. "You can also inadvertently create trans-fats at home if you fry at high temperatures and then reuse the oil," he says.
Fat and heart disease
Dr Forouhi says small amounts of butter are not associated with increased risk of heart disease. "Some studies have looked at butter in relation to heart disease, and there is no evidence that it's linked to an increased risk because it's eaten in such small amounts," she says.
However, large amounts of saturated fats from fatty and processed meats have been linked - it's important we replace these with heart-healthy fats, not refined carbohydrates, she says. "The evidence shows we should be replacing about five per cent of the saturated fat in our diets - from sources such as fatty and processed meats - with more polyunsaturated or monounsaturated fats."
The Predimed study, which looked at the effects of a Mediterranean diet on large populations in Europe, found that people who supplemented their diets with a handful (30g) of raw, unsalted nuts each day, or added extra virgin olive oil to salads, had a staggering 35-48 per cent reduction in their heart disease risk.
"We need to move away from the idea of consuming single nutrients to thinking about eating more heart-healthy foods," says Rick Miller, spokesman for the British Dietetic Association. That means a combination of saturated, polyunsaturated and monounsaturated fats for heart health.
"These include omega-3 fatty acids from fish such as salmon, herring and tuna, or plant-based sources such as walnuts, flaxseed and canola oils, avocados, olives and olive oils, and dairy products such as whole milk and eggs," he says.
"Butter seems neither bad nor good, and the evidence is unequivocal at present, so spread thinly on a nice piece of crusty bread, it's fine."