They called it Formula 47 in the US, after the total cost in cents of a burger, fries and milk shake in 1960. Formula 47 was a blend of rendered beef fat and vegetable oil, which, when used to fry shoestring slices of Russet Burbank potatoes, imparted a flavour so rich and appetising that it helped McDonald's, the restaurant selling the fries, to become the world's dominant fast-food chain. But that story turned into a cautionary tale whose lessons extend into the home kitchen. Health advocates blamed Formula 47 fries for raising customers' cholesterol, so in 1990 the Golden Arches switched to what people assumed was healthier - 100 per cent vegetable oil. The new oils were good fats that had been altered - hydrogenated - for flavour retention and longer shelf life. But that made them even more damaging to cardiovascular health than the saturated fats had been thought to be.
Some public-health experts now blame the trans fats in hydrogenated oils for tens of thousands of premature deaths. According to a recent study review by the Harvard School of Public Health, trans fats may increase your risk of a host of chronic diseases and also promote weight gain. So McDonald's and others have once again reformulated their oil, using vegetable-oil blends that are free of trans fats.
In short, oils aren't as simple as they seem. If you cook with the wrong oil, you may be sabotaging your health. To protect your body, ease your mind, and please your palate, follow these rules.
Don't rely on vegetable oil
Corn, soybean, and other vegetable oils have high levels of omega-6 fats. These polyunsaturated fats aren't bad when they're balanced with plenty of omega-3 fatty acids, such as those found in abundance in oily fish such as salmon and mackerel. But that often isn't the case in the typical western diet, though active people tend to have fairly healthy diets. "We now consume 20:1 omega-6 fats to omega-3s," says Jonny Bowden, author of The 150 Healthiest Foods on Earth. "Our inflammatory factory is overstaffed, and our anti-inflammatory factory is understaffed."
A high intake of omega-6 fats relative to omega-3 fats increases inflammation, which may increase your risk of heart disease, diabetes, and cancer, according to a 2008 review of studies by the US Center for Genetics, Nutrition and Health. There are plenty of other choices.
Expand your tastes
Not all fats are created equal. Experts say the most nutritious way to go is with a few different cooking oils to help balance your intake of omega-3 and omega-6 polyunsaturated fats, as well as saturated and monounsaturated fats. "Old Mediterranean cultures had olive oil on salad, fish at night, and then cow or goat butter or cheese, and they were more or less accidentally coming up with the one-to-one-to-one ratio," says KC Hayes, a fats researcher at Brandeis University, in Massachusetts.
Here's an easy way to balance your diet: match fats to the cuisine you're cooking. If you're making a spaghetti sauce from scratch, use a drizzle of olive oil to sauté the onions. Try coconut or peanut oil when you're whipping up an Asian stir-fry. Start an omelette by melting a little butter. The greater the variety of nonhydrogenated fats you incorporate into your diet, the better. A moderate intake of all types of nonhydrogenated fat is best, according to the American Heart Association. Wait, did we just say butter?
It's ok to use butter
Here's great news. "The health scare surrounding saturated fat and cholesterol was overblown," says Walter Willett, chairman of the department of nutrition
at Harvard University. A 2010 review of 21 studies, published in the American Journal of Clinical Nutrition, found no conclusive evidence that dietary saturated fat is associated with an increased risk of coronary heart disease, stroke or cardiovascular disease. According to
a review in the European Journal of Nutrition, a diet high in fat from dairy products such as butter may raise levels of large LDL cholesterol, which is considered relatively harmless, while having no effect on levels of potentially harmful small LDL cholesterol.
Margarine, the once-sainted substitute, usually contains at least 80 per cent vegetable oil, and that oil often contains trans fat. Butter also has trace amounts of naturally occurring trans fats, but not enough to cause concern. So you can use butter; just don't go overboard, a caution that applies to any fat. Butter is known to be an excellent source of conjugated linoleic acid, which may be a cancer-fighting nutrient, according to scientists in Ohio State University.
That doesn't mean you should kick traditionally healthy oils, such as canola
oil and olive oil, out of your kitchen. You just have to bear in mind that butter and other nonhydrogenated natural fats are not as bad as nutritionists once thought them to be. But there's one caveat. Because there always is.
Go easy in the kitchen
Oils typically contain 100 to 125 calories per tablespoon - all of them from fat - so use them sparingly. Cook smart. Usually, one tablespoon of any oil is enough to coat the pan you're using. Any more is overkill.
At the supermarket, limiting dangerous fats is easy: you can simply check labels to find products without partially or fully hydrogenated oils or trans fats. It means spending a little more time in a supermarket than seems sensible, but it is worth the effort. At restaurants, it's a little harder, though you can always ask your waiter to find out for you, and try to ignore the expression that says anything from "Are you serious?" to "What's hydrogenated?" Or, even better, use our chart (below) to cook healthier, tastier meals at home.