It was the best nutritional news anyone had read in a long time: experts were wrong to say that people should avoid butter and other saturated fats! One British newspaper even put together a “shopping list” that included cake, pie, lard and fatty cuts of meat.
Sorry, but not so fast.
In the past few years, nutritional science has developed a much more nuanced view of fat. We know it’s not all bad, and that some fats are very good for your brain and overall health. The low-fat craze of the ’80s and ’90s seems silly in retrospect. But that doesn’t mean you should be putting butter on everything.
The researchers who caused those giddy headlines were just criticizing a decision that was made decades ago — a decision that was wrong, but only because it was based on incomplete evidence available at the time. Back then, randomized studies had shown that trading saturated fat from animals for vegetable oils lowered your cholesterol. People thought that was good, but as the new study pointed out, it didn’t prevent heart attacks. Clearly, we were missing an important piece of the puzzle — but an expert panel went ahead and recommended people cut out these fats anyway. (That said, there was no evidence to recommend keeping saturated fat intakes high, given the increase in cholesterol.)
In recent years we’ve learned more. Different forms of evidence started to emerge in the 1990s suggesting that, if you replace saturated animal fats with vegetable oils, especially those with omega-3 fats, people would suffer less heart disease. These weren’t good-quality, randomized studies, but we were learning more about the heart-healthy value of omega-3 fatty acids found in canola and soybean oils.
Many of those older studies had used vegetable oil made from corn, which is high in omega-6 and very low in omega-3. A reanalysis of these studies in 2013 showed that replacing saturated animal fats with soybean oil instead of corn oil lowered heart disease. When the vegetable oil was high in omega-6s, there was no benefit, or sometimes the results were even worse.
That’s why I think it was and still is a good idea to at least partially replace butter, lard, tallow and “vegetable oil” with canola or soybean oil for cooking. Olive oil is also great, although for other reasons such as high levels of phytochemicals or monounsaturated fat. You can now buy locally made virgin canola and soy bean oils that are rich in phytochemicals.
Cholesterol is not the only thing to worry about when it comes to nutrition and heart disease. Making sure you stick to the right amount of calories to avoid obesity is much more important than tinkering with types of fat.
And if we’ve learned anything from the fat-free craze, we know that demonizing one element of our diets doesn’t always work. It seems to give us a pass to eat too much of something else that’s unhealthy.
The early studies recommended reducing saturated fat, but didn’t consider the real-world results: the low fat foods were usually higher in refined starch and sugar, and similar in calories, which could be even worse. So let’s also not assume we can start eating all the chicken-fried steak we want. Moderation is key.
Yes, there’s contradictory information out there. But there’s one way of eating that has stood the test of time. Recent high quality studies support adopting a Mediterranean-style diet. It’s plant-based, but there’s some chicken and fish, a bit of cheese, butter and nuts. To me, that’s a realistic way of eating — not only because it’s delicious. You can stick to a diet that’s influenced by southern Italy, Greece and Spain. Or just eat based on the principles of fresh fruit and vegetables, grains, nuts, beans and legumes, with small amounts of meat and dairy.
The bottom line: Too much of anything is bad for you, and it’s much easier to overeat when your food is full of sugar and fat. It is much harder to overdo it on vegetables or even fruit. Keep in mind that, even in nutrition, the dose makes the poison.
Dr. Bazinet is associate professor in the Faculty of Medicine’s Department of Nutritional Sciences and a Canada Research Chair in brain lipid metabolism. Doctors’ Notes is a weekly column by members of the U of T’s Faculty of Medicine. Email questions or comments to email@example.com .