Plant Oils Are Not a Healthy Alternative to Saturated Fat
There seems to be a long held, widespread belief that saturated fat causes bad health, especially heart disease, perhaps some cancers and other ailments. This belief has often been used to defend vegan and vegetarian diets. Unfortunately, this is a weak defense. Not only does this misguided argument illustrate the importance of relying on sound science for food and health recommendations, it undercuts the very important health message portraying the benefits of consuming whole, plant-based foods.
Now, for some specifics. Saturated fat is much more common in animal-based foods, thus inferring to most people that this is a big reason why consumption of these foods should be minimized or avoided. This story became prominent in the 1950s-1960s when comparing the health value of diets in the Mediterranean area with ‘Western’ diets commonly used in the U.S. and U.K. Diets higher in saturated fat have been shown in many studies to be highly correlated with higher rates of heart disease and certain cancers. In contrast, polyunsaturated fats (PUFAs), mostly found in plants, if anything, is inversely correlated (more PUFA, less disease) and, as a consequence, have been considered healthier.
So it went: ‘down with saturated fat-laden butter and lard, up with plant oils!’ I remember well that phase playing out in the marketplace. But also at that time, if we were to use the healthier, but liquid plant oils (more PUFAs), this presented a practical problem. People wanted fats that were solid, not liquid, at room temperature because they wanted to use this ‘oil’ to spread on their bread, like butter. To correct that problem, a chemical process was devised to bubble hydrogen through the unsaturated oil to convert them to a saturated fat, making them solid at room temperature. Unfortunately, this process led to the formation of a mostly synthetic saturated fat, now known as trans-fat. And you know this story. Evidence emerged to show that this unnatural form of fat causes heart problems.
The evidence that saturated fat is a major cause of heart disease, and possibly certain cancers, arises primarily from studies showing a high correlation between saturated fat-laden diets with more heart disease. This is a classic case where correlation does not necessarily mean causation, a serious misinterpretation. Blindly accepting saturated fat as the causation of heart disease was a mistake. It is not biologically plausible, and this relationship should have been questioned. Let me further explain.
Although typically ignored, dietary saturated fat (and its fat companions: dietary cholesterol and total fat) is also highly correlated with animal protein-based diets. But seriously, who would dare to question protein, the bastion of animal-based foods? For over a century, compelling evidence (in rabbit experiments) showed very specifically that animal-based protein, was MORE effective than dietary cholesterol in raising blood cholesterol and causing ‘heart disease.’ Later, evidence, both in animal and human studies showed that this protein effect on blood cholesterol and early atherogenesis (cardiovascular disease) referred to animal-based protein, not plant-based protein. In short, animal-based protein is more hazardous than lipids (cholesterol and fatty acids).
Then, there’s another twist that is very important to consider. Unsaturated fat (PUFAs) are susceptible to tissue damaging oxidation, and saturated fat is not. Oxidation brings into consideration the formation of chemically reactive oxygen (as ‘reactive oxygen species, ROS) that causes aging and increases cardiovascular disease and cancer. For example, plant oils experimentally promote cancer much more than does saturated fats—that’s right. This is an experimental observation that is at least 30-40 years old.
From a practical perspective, however, this mainly refers to added oils-isolated from plant sources. It does not refer to the oil within those plant-based foods because plants contain lots of antioxidants to keep the tissue damaging effects of ROS under control. In my opinion, this is a primary reason for avoiding consumption of added oils. Another reason for avoiding these oils is their contribution to total calorie intake which displaces, in effect, the consumption of calorie containing whole, plant-based foods.
It should be emphasized, however, that excess saturated fat in the diet, although not causal, is a very good indicator of an unhealthy dietary practice. It indicates the dietary presence of saturated fat-laden, animal-based food (meat, milk and eggs) and for many, the presence of added fats like saturated fat-laden butter and lard derived from milk and meat, respectively. It does not say that saturated fat is the cause of diseases promoted by these foods.
Focusing on fat as the main culprit of an unhealthy diet is seriously misguided for a variety of reasons.
- It detracts from the health problems caused by animal-based foods, which primarily owe their unhealthy properties to their protein content far more than their content of lipids like cholesterol or saturated fat. Animal-based protein not only stimulates mechanisms (e.g., higher ROS) that lead to diseases like cancer and heart diseases, it also depresses mechanisms designed to protect us from those diseases. Increasing, in turn, the consumption of animal-based foods decreases the consumption of whole, plant-based foods that protect us from heart disease and cancer. If this recommendation is primarily tied to saturated fat, a false premise, it is much easier to discredit it—and this is in fact happening!
- Blaming the prohibition of animal-based food on a false saturated fat (or cholesterol or total fat) argument actually led to attempts over several decades to remove fat, especially saturated fat, from these foods—as in skimmed milk and many other low fat products—and create a healthier alternative. Little or no health gain has been noted.
- Shifting to a healthier alternative to saturated fat, as with the use of plant oils (e.g., oleomargarine) and related synthetic products causes us to jump from the frying pans into the fire (almost literally!) only to suffer more and die earlier.
- Falsely focusing on saturated fat as a health villain, a widely held view, allows food and health policy boards to make relatively useless propositions on a relatively trivial concern thus diverting their attention away from what they ought to be doing.
I have been concerned with this topic since the 1970s. To this day I cannot accept the saturated fat proposition. Since then, this position on saturated fat (and cholesterol) has almost become a biblical verse, so to speak. In those days I was making the same point, with less supporting evidence. I predicted that public focus on dietary cholesterol and saturated fat (as causes of heart disease and/or cancer) would someday come back to haunt us, and, so it goes.
Copyright 2019 Center for Nutrition Studies. All rights reserved.