Saturated fat not the pure villain we think
Saturated fat developed a bad rap about 50 years ago when it became linked with elevated cholesterol levels and heart disease. That ushered in the era of the low-fat diet, which in hindsight turned out to be not so terrific.
Special to The Times
Confused about saturated fat? You aren’t alone.
Saturated fat developed a bad rap about 50 years ago, when it became linked with elevated cholesterol levels and heart disease. That ushered in the era of the low-fat diet, which in hindsight turned out to be not so terrific. Neither did swapping the saturated fats in butter for the trans fats in stick margarine.
The role of dietary fats in heart disease and other diseases is complex. One reason is fat in foods is generally a mix of saturated, polyunsaturated and monounsaturated, even if one type predominates.
Another is no fat or food exists in a vacuum. When considering fat, we also need to consider our overall diet.
Just as our bodies need some cholesterol, they also need some saturated fat for various body functions. What we think of as a single entity — saturated fat — is in fact a class of several fatty acids. These fatty acids have different effects on the body, some positive, some neutral, some detrimental.
Saturated fats are primarily found in animal foods (meat, dairy and eggs) as well as coconut oil, cocoa butter and palm and palm-kernel oils.
Major sources of polyunsaturated fats (the omega-6s and omega-3s) include vegetable oils (safflower, corn, sunflower).
Sources of monounsaturated fats include olive oil, avocado and macadamia nuts.
Science has established that saturated fat increases blood levels of low-density lipoproteins (LDL), aka “bad” cholesterol, and that a diet rich in polyunsaturated fat decreases LDL.
However, this is only part of the picture. Associations between intake of saturated fats and rates of heart disease have been noted for decades, yet no one knows exactly how saturated fats could cause heart disease (i.e., no physiological mechanism has been found).
The fact that eating saturated fat can increase LDL cholesterol isn’t the key, because what matters more than cholesterol levels per se is whether that cholesterol becomes oxidized. (Think of oxidation as rust in your body.) Oxidized cholesterol is a major player in plaque buildup in the arteries.
Another interesting point is that saturated fat is less likely to cause systemic (body-wide) inflammation than polyunsaturated fats. Inflammation is a known risk factor in heart disease, cancer and other conditions.
The stigma against saturated fat lingers despite recent research that puts it in a new light. Some of that research involves what happens when we reduce saturated fat and replace it with something else:
• Replacing saturated fat with polyunsaturated or monounsaturated fat lowers total cholesterol and the bad LDL, but can also lower high-density lipoproteins (HDL), aka “good” cholesterol.
• Replacing fat with carbohydrates has been shown to increase blood triglyceride levels as well as a small, dense type of LDL cholesterol particles that are more strongly linked to heart disease than total cholesterol or “regular” LDL. This is particularly true if refined carbohydrates, such as sugar and white flour, are a large part of the diet.
Next week: Sources of saturated fat, and tips on how to eat happily and healthfully with or without it.
Carrie Dennett is a registered dietitian/nutritionist with a master of public-health degree in nutritional sciences from the University of Washington. Her blog is nutritionbycarrie.com.