I like to believe I can update my beliefs when presented with new evidence or a better interpretation of the same body of evidence, rather than clinging to my old beliefs. In the next two posts, I’ll discuss two examples where that has happened. Years ago, I argued that butter may make positive contributions to health. My thinking has gradually evolved since then, and I now think less refined forms of dairy are preferable to butter. Here’s why.
The whole food heuristic
Heuristics are simple rules that get us most of the way to the truth. One of the most valuable heuristics in nutrition is also one of the simplest: eat minimally refined foods. This single-handedly eliminates nearly all of the calorie-dense, nutrient-poor ingredients and foods that contribute to obesity and noncommunicable disease. The whole food heuristic is not only supported by a large and growing body of evidence, it’s also consistent with evolutionary considerations and common sense.
Food refining is a continuum. For example, when considering sugar, whole fresh fruit is a minimally refined source, while white sugar is a maximally refined source. Fruit leather and fruit juice are somewhere in between. Where is butter on that continuum? It’s not as refined as liquid seed oils, which are typically solvent extracted, degummed, bleached, and deodorized. It doesn’t require industrial technology to produce. But it’s certainly much more refined than milk, the whole food it’s derived from. To illustrate this, consider that typical milk only contains 3-4 percent fat by weight when it comes out of a cow. Making butter is a process of concentrating a small fraction of milk by 30-fold. And as a result, a wide variety of nutrients are separated out and calorie density increases greatly.
Dairy fat may still have nutritional value, but why not eat it in a less refined form that is more nutritious and less calorie-dense?
Circulating lipoproteins influence cardiovascular disease risk, and LDL is a particularly important one. Things that increase the number of LDL particles, and/or their total cholesterol cargo (called LDL cholesterol) tend to increase cardiovascular disease risk. The evidence supporting this is now extremely strong (1, 2).
As it turns out, butter increases LDL cholesterol and particle number more than most other fats (3, 4, 5, 6). While butter also increases “good” HDL cholesterol, recent drug trials have questioned the causal relevance of increasing HDL cholesterol, meaning that it may not actually protect you from an increase in LDL cholesterol (7).
Recent evidence suggests that the effect of dairy fat on LDL cholesterol depends heavily on the context in which the fat is delivered. Less refined forms of dairy such as yogurt, cheese, and cream have little effect on LDL cholesterol, even when they deliver the same amount of dairy fat as butter (8, 9, 10, 11)! Some research suggests that this is due to a protective substance in less refined dairy foods called the milk fat globule membrane, which is lost during the butter-making process (12).
Face it: the main reason we eat butter is that it tastes amazing. And this is no surprise. Butter is one of the most calorie-dense foods in the world, and the human brain likes calories (for an explanation of why, see my book The Hungry Brain). Most of us eat too many calories, and butter isn’t helping.
Fat isn’t automatically fattening, but research suggests that it can be fattening when it meets two criteria: high calorie density and high palatability. Butter gets near-maximal scores on both. Why not get the same nutrients and more from yogurt, which is less calorie-dense, less extreme in palatability, more sating per calorie, and therefore more likely to favor a healthy calorie intake?
The whole food heuristic is probably the simplest and most effective diet rule we have, and it suggests that whole sources of dairy should be healthier than butter. Research in the areas of cardiovascular disease and appetite control are increasingly supporting this prediction.
That said, butter isn’t toxic, and if you want to use a little to saute onions or mix into steamed vegetables, I doubt it will have much negative impact on an otherwise healthy diet. But extra-virgin olive oil is probably better for cardiovascular health, and if you choose to eat dairy, it may be preferable to focus on less refined forms of it, particularly yogurt.