Facts about fats

Dear Alice,

I know it's necessary to have a certain amount of fat in your diet, but occasionally I hear about "good fat" and "bad fat." What is the difference? Is that the same as saturated/unsaturated? What foods have "good fat"? Can I tell by looking at the nutrition label on a food product which kind of fat I'm eating?

— Curious

Dear Curious,

The "good fat versus bad fat" you've heard about really refers to a particular type of fat's potential risks to your health. But, there’s more to fats than just health risk. Fats are a key component of a balanced, tasty diet and are essential for cell growth, providing energy, helping to absorb vitamins, and helping you to feel full. What is inherently present in the “good versus bad” discussion, though, is that while there are some similar components, fats aren’t created or behave in the same way. For instance, all fats have the same amount of calories, but they vary in their chemical compositions and effects on health. Saturated, monounsaturated, and polyunsaturated are found naturally and some trans fats are chemically-produced (but not all). Some fats, such as the unsaturated variety, are associated with benefits to your health, whereas others, such as the saturated and trans types are often linked to health risks. To help you figure out what types of fats are in the food you’re consuming, nutrition facts labels do indicate saturated and trans fat, helping you make decisions that are appropriate for you. Read on for more detail about each of these types of fat.

From a technical perspective, unsaturated fats are those that have a double bond between carbon molecules. These fats are generally liquid at room temperature, although they may begin to solidify if they’re cooled. These fats can be broken down into two subtypes:

  • Monounsaturated fat is found in olive oil, canola oil, peanut oil, and in most nuts and nut butters. It has been found to improve cholesterol levels, which can then reduce cardiovascular disease risk. There is also evidence that monounsaturated fats may benefit the insulin levels and control blood sugar for those with type 2 diabetes.
  • Polyunsaturated fats are separated into two major categories: omega-3 and omega-6 fatty acids. Polyunsaturated fats can help to improve blood cholesterol levels, regulate blood sugar, reduce triglycerides, and regulate blood pressure. Omega-3s are used by the body to produce hormone-like substances with anti-inflammatory effects. The sources rich in omega-3s are fatty fish, such as salmon, sardines, mackerel, herring, and rainbow trout, among others. Canola oil, walnuts, and flaxseed also contain some omega-3s. Omega-6 fats are found in oils such as corn, soybean, cottonseed, sunflower, and safflower.

The amount of unsaturated fats is sometimes listed separately on the nutrition facts label, but when it’s not, it can be calculated by subtracting the saturated and trans fats from the total fat. Omega-3 and omega-6 fatty acids generally aren’t listed individually on the nutrition facts label, though some foods may tout that they contain them.

Saturated fat is primarily found in high-fat cuts of meat, poultry with the skin, whole and two percent dairy products, butter, cheese, and certain oils: coconut, palm, and palm kernel. Only a small amount (less than ten percent of calories) of saturated fat is needed each day, but the typical American diet usually exceeds that amount. Too much saturated fat may cause a person's low-density lipoproteins (LDL), the cholesterol that can block arteries, to rise. You can look for the amount of saturated fats in a serving of food on the nutrition facts label, under the heading "Saturated Fat" below the larger heading of "Total Fat."

Trans fats are manufactured by chemically altering oils to make them solid at room temperature — though some also occur naturally. In the past, trans fats were widely used in foods as a replacement for saturated fats. Then it was discovered that trans fat, in addition to raising LDL cholesterol (as saturated fat does) it also decreases the level of high-density lipoproteins (HDL), which is responsible for bringing the LDL to the liver for clearance out of the body. All companies are now required to list the amount of trans fats on the nutrition facts label. However, there’s a caveat: products containing half a gram or less of trans fat per serving are permitted to report zero grams of it on the nutrition facts label. However, even if the nutrition facts label reports no trans fats, the ingredients list can still indicate if any may be present. If you see the words "partially hydrogenated" or "hydrogenated" in front the word “oil,” the food probably has a small amount of trans fat. They can be found in fried foods, baked goods, prepackaged foods, creamer, and margarine to name a few.

In general, the secret isn't to stay to one extreme or another when it comes to fat in your diet. Though it’s noted that too much saturated and trans fat may result in negative health consequences, consuming too much fat — no matter the type — may lead to health risks. Finding a balance is key. There’s no need to be "all or nothing" when it comes to fat in your diet, so here's to maintaining moderation!

Last updated Nov 29, 2019
Originally published Mar 22, 2002

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