It started in the 1950s with a case of mistaken identity. Saturated fats, researchers said, were the main cause of heart disease. The smoking gun? Fatty deposits in patients’ arteries and studies showing that people in Mediterranean countries – where people tend to eat more unsaturated fats like olive oil than saturated fats like butter – had a lower risk of disease.
By the 1970s the food industry responded. Their answer was trans fatty acids, or trans fats: unsaturated fats transformed by hydrogenation to fit convenient criteria. Once hydrogenated, for example, cotton or vegetable oils would be solid at room temperature to make margarine. Fats could be chemically tweaked to increase the shelf life of biscuits and cakes, or to avoid them from breaking down during the repeated reheating done in chip shops and restaurant
That these trans fats were made from unsaturated ones, the thinking went, meant they were healthier than saturated fats. It was a misconception supported by the medical community; and one which proved to be deadly.
The increased consumption of trans fats contributed to a peak of heart attacks and strokes during the 1980s and 90s. Eating them, it turns out, can also increase your risk of type-2 diabetes, so there’s little wonder that manufacturers, at the behest of governments, have been reducing the amount of trans fats in their products.
“There’s still no legal requirement for companies to label trans fats as such,” warns Chloe Miles, of the British Dietetics Association. “It’s important to check the ingredients lists. Look out for anything with partially hydrogenated oils or fats. The usual suspects are takeaways, pastries, pies, fried foods, cakes, biscuits and hard margarines.”
Ding dong, pseudoscience nutritionists proclaimed at the outing of trans fats, the witch is dead! But they fell into a dangerous trap: they started saying that saturated fats such as butter and coconut oil are good for you. This is by no means true. Though angelic compared with trans fats, eating too much saturated fat will damage your health by displacing healthier foods. Trying to replace saturated fats completely with low-fat options, though, means you’ll be eating more sugar and refined carbohydrates, which will do you worse, so saturated fats should be used wisely to make some healthy foods more satisfying.
The heroes are unsaturated fats from whole food sources. Olive oil, seeds, nuts, oily fish and avocados, if prioritised over saturated fats, can help you lose weight and avoid heart disease. And they may even protect against neurological disorders such as depression. The health benefits of these fats is a simple message that should not get lost in a complicated history.