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Good Fats, Bad Fats, Worst Fats

Figuring out the Fats

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Olive oil has high levels of monounsaturated fats
Bruce Law/Stockbyte/Getty Images

Conventional wisdom on dietary fats has changed. Once, all fats were deemed unhealthy, and responsible for all manner of diseases, from cardiovascular disease to diabetes. But years of research have changed our thinking. We now start with the premise that all fats are not created equal—that there are good fats, bad fats, possibly-not-so-bad fats, and very bad fats. Let's take a closer look:

The Good: Unsaturated Fats

Even today, some people need convincing that the term good fats is not an oxymoron. These unsaturated fats help fight the very diseases that consuming excess fat was said to cause. Unsaturated fats are divided into monounsaturated fats and polyunsaturated fats, and both types are thought to have beneficial effects on cholesterol levels.

Monounsaturated fats help lower LDL (bad) cholesterol while also boosting HDL (good) cholesterol.

Polyunsaturated fats are also thought to help lower total and bad cholesterol. But monounsaturated fats tend to be favored over polyunsaturated fats because some research suggests that polyunsaturated fats are less stable, and can reduce levels of good cholesterol as well as bad.

But let's not ignore polyunsaturated fats. These are often a good source of omega-3 fatty acids, found mostly in cold-water fish, nuts, oils and seeds, and also in dark leafy greens, flaxseed oils and some vegetable oils. One kind of omega-3 fatty acid is an "essential fatty acid," which cannot be manufactured by our bodies, so eating these foods is the only way to get them. Omega-3 fatty acids are thought to lower blood pressure, combat LDL (bad) cholesterol, fight inflammation and protect the brain and nervous system.

Most cooking oils are made up primarily of unsaturated fats. When it comes to choosing cooking oils, each type of cooking oil varies in its ratio of monounsaturated to polyunsaturated fats. Two oils stand out for their high levels of monounsaturated fats: canola oil and olive oil. Other than nonstick cooking spray, these two oils should be in your pantry.

At the end of the day, a good fat is still a fat in terms of calories. Any labels on cooking oil that describe the oil as "light," are referring to the taste or color, not the fat or calorie content. All oils are 100 percent fat and are worth around 120 calories per tablespoon.

The Bad: Saturated Fats

Then there are the so-called bad fats—those apparently "artery-clogging" saturated fats from meat and dairy products. These fats are solid at room temperature. Saturated fats have been shown to directly raise total and LDL (bad) cholesterol levels. Conventional advice has been to avoid them as much as possible. However, a meta-analysis published in the Annals of internal medicine in March 2014 and another in the American Journal of Clinical Nutrition in early 2010 found no link between saturated-fat intake and increased risk of coronary heart disease or cardiovascular disease. Still, the Harvard School of Public Health, in a study published in March 2010, found that replacing saturated fats with an equal amount of polyunsaturated fats did indeed reduce the risk of coronary heart disease by 19 percent.

Perhaps, then, saturated fats may not be so bad after all, and they are certainly an important source of vitamins and minerals. Plus, some argue that coconut oil and palm fruit oil, which are plant-based sources of saturated fats, may actually be beneficial because their particular fatty-acid make-up means they are metabolized differently in the body. Stearic acid, found in animal products and in some foods such as chocolate, gets a pass because much of it is converted by the body into oleic acid, a monounsaturated fat. Thus, saturated fats may be more beneficial, or at least more neutral, than we think. Yet although there are more and more scientific studies suggesting this is the case, there is, paradoxically, no broad consensus on this yet, especially among those designing dietary guidelines. The advisory committee for the 2010 Dietary Guidelines for Americans suggests a reduction of saturated-fat intake to no more than seven percent of daily intake, and little recognition that a high intake of carbohydrates, which tend to replace saturated fats in people's diets, are a factor in rising obesity rates and associated health problems.

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