When I was a kid in the 1970s, one of the biggest debates in our household had to do with what we should spread on our toast. On the one hand, butter had been a staple of the American diet for centuries, but experts recently had begun to push margarine as a healthier substitute. Butter, after all, was full of “unhealthy” saturated fat; indeed, it contained more saturated fat than just about anything else in the typical Western kitchen at the time, although cheese, cream, and other dairy products (as well as certain nondairy animal products) came close. On the other hand, margarine was made in a lab from “healthier” vegetable fats: the unsaturated fats found in (for instance) soybean or safflower oil.
There was just one problem: at room temperature, vegetable oils are liquid. No one wants a soggy, wet piece of toast. To make margarine solid, food scientists subjected vegetable oils to a process called hydrogenation, in which hydrogen gas was mixed with the oils while exposing them to a metal catalyst and subjecting them to heat and pressure. This process created oils that were solid at room temperature and, at least at first, tested quite well in marketing research. Many people, even cardiologists, began to push margarine as a “hearty healthy” substitute for butter. It became the spread of choice in the Carroll household.
Of course, today we know “hydrogenated oils” by another name: “trans fats.” And now we know they’re terrible for us ?— ?even worse than saturated fats. Yet the margarine-induced assault on butter continues to this day and has led people to spurn many of its saturated-fat cousins as well.
The impact of this low-fat craze on our health has been dubious, to say the least. It turns out that alternatives to saturated fats ?— ?including, but not limited to, trans fats ?— ?are not nearly as good for us as we were led to believe. And there’s another wrinkle. Those saturated fats we thought were so bad for us? They actually might not be.
The truth about trans fats
By the 1990s, evidence was building that trans fats carried a significant risk of coronary heart disease. Today, they’ve been found not only to increase levels of low-density lipoprotein (the “bad” cholesterol ?— ?more on this in chapter 3) but to also decrease levels of high-density lipoprotein (the “good” cholesterol). By both lowering LDL and increasing HDL, trans fats have about twice the negative impact as saturated fats. And that’s not all. Trans fats also increase triglycerides, fats that our body can use for energy but that are also thought to be associated with cardiovascular disease.
Unlike many other areas of nutrition science, there is some high-quality research to support the conclusion that trans fats are bad for our health. In 2006, the New England Journal of Medicine published a huge review article that began to sound the death knell for trans fats. The researchers conducted a meta-analysis of twelve randomized controlled trials of trans fatty acid consumption through 2005. They found that compared to eating saturated or unsaturated fats, eating trans fats significantly increased pretty much all the risk factors for coronary heart disease. Trans fats also appeared to increase the markers of inflammation in the body and decrease the effectiveness of the cells that work to keep the blood vessels clean. On a per-calorie basis, trans fats increased the risk of coronary heart disease more than any other nutrient.1
Throughout this book, I discuss how the dire warnings we hear about many ingredients seem to be overblown. I don’t take that approach with trans fats, however, because the evidence against them is pretty damning.
I’m not alone in this conclusion. In recent years, artificial trans fats have been almost entirely eliminated from the American diet. Months before the study in the New England Journal of Medicine was published, the Food and Drug Administration ruled that companies had to start explicitly labeling how much trans fats their foods contained. Fast-food retailers such as McDonald’s and Burger King began eliminating artificial trans fats from their products, and the tiny amounts that remain occur naturally in meat and cheese. New York City banned them in restaurants in 2007, and the Centers for Disease Control and Prevention argued that removing trans fats from the U.S. food supply could prevent about 20,000 heart attacks a year and 7,000 deaths from cardiovascular disease. In response, the FDA issued a Federal Register notice announcing that the agency believes that trans fats are not “generally recognized as safe.” Such a notice allows a period of time for people and businesses to comment and offer opinions and evidence as to why the determination should not result in a ban. Nothing convincing came of this, and in 2015 the FDA finalized its determination that trans fats are generally not recognized as safe.
In the butter versus margarine debate, the Carroll family should have stuck with butter. And that’s not the only match in which butter appears to win out. It seems that not only are saturated fats much better for us than trans fats, but they also may not be that much worse for us than a range of other fats ?— ?including many that have been championed as “healthier” alternatives.
You read that right: butter, and the fats it contains, are not only likely to be part of a healthy diet, but they may actually be better for us than many alternatives. Frustratingly, the evidence to prove this has been out there for decades. It just hasn’t been given a fair shake until very recently.