In a new book, Jennifer McLagan questions scientific basis for the low-fat diet and opens up our menus.

Fat finds itself in and out of fashion more frequently than flares and leggings. One minute we are being urged to avoid it and told that very low-fat diets are the way to go; the next we are encouraged to gorge on it, Atkins-style. Throughout fat’s fluctuating popularity, there has been one constant: that saturated animal fats are bad, bad, bad for the heart and we consume too much of them at our peril. But is even this accepted wisdom a big fat lie? That is the case argued in a controversial new book by a leading Canadian chef and food expert. She suggests that saturated fat’s killer reputation is wholly undeserved.

In Fat: An Appreciation of a Misunderstood Ingredient, Jennifer McLagan not only questions the scientific basis for a low-fat diet, but argues that many of our health woes have arisen from our attempts in recent years to cut down on butter, lard, suet and other saturated animal fats. She argues we should be eating more, not less, of them. “You can’t live without fat,” she says. “It gives us energy and boosts the immune system. Some fats have antimicrobial properties, others lower bad cholesterol. Your brain is made of fat and cholesterol, as are the membranes of your cells.”

McLagan claims that much of the bad rap surrounding saturated fat stems from flawed studies that were carried out between the 1950s and 1970s, mostly by the American physiologist Ancel Keys. It was Keys who first came up with what is known as the diet-heart hypothesis, after some of his research showed that a high intake of animal fat not only raised cholesterol levels but was strongly linked to heart attacks. His findings prompted medical experts around the world to change dietary recommendations to those that are still heavily promoted today: in short, cut down on animal fats for the sake of your heart.

Certainly, it is almost impossible to find nutrition health campaigns that advocate eating more animal fat. Even those behind the Atkins diet, who once encouraged followers to eat fatty foods, are now promoting a toned-down plan, with more lean meat and fish than sausages, cheese and bacon. Recent research into what has been dubbed the “eco-Atkins” approach at the University of Toronto showed that a low-carbohydrate diet in which animal protein was replaced by vegetable sources, such as soy, wheat (gluten) and nuts, not only reduced weight but lowered blood pressure and cholesterol more effectively than other diets. “We took out the saturated fat and cholesterol and put in vegetarian protein sources,” says Dr David Jenkins, a professor of nutritional sciences, who led the research. “We know that nuts lower cholesterol and prevent heart disease, and soy is eaten in the Far East, where they don’t get much heart disease. So these foods can be put together as protein and fat sources.”

However, there are many who remain sceptical about fat’s role in heart disease, claiming that gaping holes existed in the research that led to saturated fats being branded a killer. In one of his landmark studies, for instance, Keys looked at animal-fat consumption in seven countries. Although he found a high intake was a strongly linked to heart disease, the data wasn’t rock solid, and in three of the countries studied there was no clear link. Other researchers have failed to show animal fat is as harmful as we are led to believe. In one of the largest government-funded research programmes in America, the Women’s Health Initiative study, carried out at the Fred Hutchinson Cancer Research Center in Seattle in 2006, a diet low in total fat and saturated fat was shown to have no impact in reducing heart disease among nearly 49,000 women who took part.

Glenys Jones, a nutritionist at the Medical Research Council’s human nutrition research department in Cambridge, says that saturated fat does have an undeservedly poor reputation. “There are different forms of saturated fat, and the fat in red meat, for example, is a form called stearic acid, which isn’t linked to heart disease,” she says. “Other forms, such as the fat in butter, have a much stronger association, and, of course, too much of any fat will result in obesity, which is itself a risk factor for heart disease.” Such confusion, McLagan says, means that “nobody has ever been able to prove the supposed link between a diet high in animal fat and cardiovascular disease, and that’s why we have people such as the Inuit, who eat a lot of animal fat and who do not have high rates of heart disease”.

Over the past 30 years, McLagan says, the move away from saturated fat has had no effect on lowering the incidence of cardiovascular disease. What happened instead, she says, is that people switched to margarine and spreads made from trans fats, which have since been found to be more harmful than saturated fats in causing diabetes and obesity. Our preference for vegetable oils has brought additional health issues. While fish oils are rich in heart-healthy omega-3 essential fatty acids, most vegetable oils, including sunflower and corn oil, are high in the much less beneficial omega-6, of which we already consume too much — the average UK diet has an omega-3 to omega-6 ratio of 1:10, whereas the recommended ratio is 1:3. “An excess of omega-6 has been linked to a range of killer diseases,” says McLagan. “Too much of it also inhibits our uptake of omega-3 from food.” And, after fish oils, what, according to McLagan, is one of the best food sources of omega-3? You guessed it: animal fat.

So what are we to do? Bridget Benelam, a nutrition scientist at the British Nutrition Foundation, agrees that negotiating the fat maze is not easy. “It is really difficult to prove causal links between diet and disease,” she says. “It is accepted that there is enough evidence that excessive amounts of saturated fat increases the risk of heart disease. But it is only one of the factors. We don’t need to avoid animal fat completely and there’s no reason why we can’t have moderate amounts of it in our diet.”

This is not a green light to gorge on bacon sarnies and fried bread. Too much fat will still make you put on weight, and Benelam stresses that, on average, our intake of saturated fat is one-fifth more than the upper limit set by the government. “Sometimes health messages get distorted and misinterpreted,” she says. “The truth is that nobody has ever said people should cut out animal fats completely. The aim should be to reduce overall fat intake to within healthy limits. Then you can enjoy a little butter on your toast.”

FACE THE FACTS

1 The current UK health recommendation is to get no more than 35% of your total calorie intake from fat. No more than 11% of that total should be saturated fat derived from animals.

2 The recommended upper limit for women is a daily total of 70g of fat (20g of which can be saturated) and for men 95g (30g of which can be saturated).

3 Trying to determine fat content from food labels can be confusing. For instance, the terms ‘light’ and ‘lite’ have no legal definition and can actually refer to the colour of a food. For a food to be labelled ‘low fat’ it must contain no more than 3g of fat per 100g.

4 Learning to decipher fat figures yourself is the safest bet. According to the Food Standards Agency, a high-fat food contains 20g or more of total fat (5g of saturated fat) per 100g. Look instead for low-fat foods containing 3g of total fat (1.5g of saturated fat) or less.

5 ‘Be wary of claims that a food is 90% fat free,’ says Louise Sutton, a dietician at Leeds Metropolitan University. ‘It does not mean it is a low-fat food because the remaining 10% of that product is fat. And in some cases, low-fat foods are high in sugar.’

Sunday Times Style - 12/7/09