Saturated Fat: Not Quite So Bad After All

The common wisdom about healthy eating, among nutrition experts as well as the public, is almost always called into question eventually. Not so surprising, since it’s hard to tease apart the health effects of individual nutrients (say, vitamin E or protein) or even specific foods (margarine or eggs), which are consumed as part of complex diets that change over time and interact with genetic, environmental, and lifestyle factors. Thus, the job of giving dietary advice takes some hubris, or perhaps wishful thinking, as well as the ability to take one step back after taking two steps forward.

Case in point: For years fat was seen as public enemy No. 1, until studies found that low-fat diets do not improve the odds of preventing disease or losing weight. Dietary cholesterol was feared as much as fat, until it was discovered that most people can eat an egg or two a day without increasing their risk of heart disease. Okay, so total fat intake and dietary cholesterol are not the main problems, but at least we’re certain that saturated fat (found primarily in animal products such as meat, butter, and milk) is the leading dietary culprit behind high blood cholesterol, “clogged” arteries, and heart disease. Right? Well, maybe not.

Though saturated fat raises LDL (“bad”) cholesterol, this is offset somewhat by the fact that it mostly increases levels of larger LDL particles, which are now known to be less dangerous than smaller ones). This finding comes in part from research by Dr. Ronald Krauss, director of Atherosclerosis Research at Children’s Hospital Oakland Research Institute, a member of our Editorial Board, and coauthor of our 2010 Wellness Report Controlling Your Cholesterol. Dr. Krauss and his colleagues discussed this and other evolving research concerning saturated fat in an article in the American Journal of Clinical Nutrition in March.

Not so black or white
The effect of saturated fat on blood cholesterol, like many other nutritional matters, varies from person to person, depending on genetic factors, body weight, and even gender (cutting down on saturated fat tends to lower LDL more in men than in women). It also depends on where the fat comes from. The saturated fat in chocolate, for instance, is composed of different fatty acids than that in beef and appears to be more neutral in its effect on blood cholesterol levels. And foods contain other substances besides saturated fat that also affect the risk of heart disease. Thus, it’s hard to generalize about isolated nutrients when context is so important.

The key point, according to Dr. Krauss, is not that saturated fat is completely off the hook, but rather that it’s essential to focus on what you eat in place of the saturated fat. If you cut down on certain types of foods, you end up eating more of something else. And when people reduce saturated fat, they tend to replace it largely with refined carbohydrates, such as white breads, pasta, and sugary baked goods. Unfortunately, this tradeoff often has an adverse effect on blood cholesterol—lowering HDL (“good”) cholesterol and increasing triglycerides and the more dangerous, smaller LDL particles. Switching to foods containing trans fat is an even worse step.

On the other hand, replacing saturated fat with polyunsaturated fat (as in most vegetable oils and margarine) improves cholesterol levels. It also significantly reduces the risk of heart disease, according to a recent Harvard analysis of eight clinical trials in the open-access journal PloS Medicine. Fiber-rich foods—notably vegetables, fruits, and whole grains—are also good substitutes for animal fat. So are nuts and fatty fish; the latter supplies polyunsaturated fats called omega-3s, which are particularly heart-healthy.

Keep in mind: All fats and high-fat foods are high in calories. So whatever dietary changes you make, be certain you don’t end up consuming more calories, since weight gain and especially obesity have adverse effects not only on cholesterol levels, but also on nearly every aspect of cardiovascular health.

UC Berkeley Wellness Letter, June 2010

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