How “Bad” Fats Affect Cholesterol

Selection of bad fat sources

Saturated and trans fats are both unhealthy fat sources that can wreck havoc on your cholesterol levels when consumed in excess.

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Your body makes all the cholesterol you need, and if you eat a diet high in unhealthy saturated and trans fats, you can add to your cholesterol total and potentially hasten the buildup of fatty plaques in your arteries.

Fats were once considered the bane of healthful diets. To stay healthy or lose weight, you needed to follow a low-fat eating plan. Indeed, saturated fat and trans fat have remained dietary pariahs, primarily because of their negative effects on cholesterol.

But, there’s no need to be completely fat-phobic. Not all fats are created equal, nor are they equally bad for you. In fact, some fats are good for you, and the 2015-2020 Dietary Guidelines for Americans do not set a limit on total fat intake. Rather, the key is to switch from bad fats to healthful fats.

The Bad Fats

Saturated fats have been shown to increase total cholesterol and LDL levels. Most of the saturated fat you consume comes from animal products like beef, pork, lamb, poultry with skin, many processed meats (e.g., bacon, hot dogs, bologna, salami, sausage), and full-fat dairy products, such as cheese, butter, ice cream, and whole milk. Some oils derived from plants—for example, coconut oil, palm oil, palm kernel oil, and other tropical oils—also contain saturated fat.

The Dietary Guidelines for Americans recommend limiting your intake of saturated fat to no more than 10 percent of your daily calories (about 22 grams of saturated fat for a 2,000-calorie-a-day diet) and trans fat to as close to zero as possible. The guidelines panel noted that “dietary advice should put the emphasis on optimizing types of dietary fat and not reducing total fat.” The American Heart Association (AHA) suggests trimming your saturated fat intake even further, to less than 5 to 6 percent of your daily calories, or about 11 to 13 grams of saturated fat if you eat 2,000 calories a day.

To cut down on saturated fat, replace fatty meats with skinless poultry, avoid processed meats and fried foods, substitute low-fat or fat-free dairy products for full-fat versions, and use unsaturated fats (such as olive, canola, soybean, and corn oils) instead of lard or butter. Read the Nutrition Facts label on the foods you buy and choose products with no more than 2 grams of saturated fat per serving.

Most trans fat is manufactured during a process called hydrogenation, which makes liquid fats (oils) more solid and increases their shelf life. Partially hydrogenated vegetable oils are the source of about three-quarters of the trans fat in the American diet. Trans fats are especially harmful because they can increase LDL cholesterol, reduce beneficial HDL cholesterol, promote inflammation, and possibly contribute to insulin resistance.

In 2015, the U.S. Food & Drug Administration (FDA) ruled that partially hydrogenated oils are no longer generally recognized as safe and set a deadline of June 18, 2018, for them to be removed from the food supply. This deadline applied to the majority of uses for partially hydrogenated oils, and most manufacturers have complied with the FDA action. However, to allow extra time for products made before June 18, 2018, to move through the distribution process, the FDA extended the compliance deadline to Jan. 1, 2020, for these foods. The FDA also extended until June 18, 2019, the deadline for manufacturing of foods with specific petitioned uses of partially hydrogenated oils and set Jan. 1, 2021, as the deadline for those products to work their way through distribution.

So, trans fat in the form of partially hydrogenated oils, although greatly reduced, has not yet been eliminated completely from the food supply. (Trans fat occurs naturally in small amounts in some animal foods.) Historically, some of the products containing the highest amounts of trans fat have included cakes, pies, doughnuts and other bakery items, as well as frostings, non-dairy creamers, microwave popcorn, and stick or tub margarine.

Carefully read the ingredients list of any food product you purchase, not just the Nutrition Facts label. As long as a product has less than 0.5 grams of trans fat per serving, the manufacturer can claim it has zero grams of trans fat, according to FDA regulations. Avoid products containing “partially hydrogenated” oils, especially if that term appears near the top of the ingredients list.

The Friendlier Fats

Fats, in general, have received a bad rap, but not all fats are bad. While trans fat and saturated fat can adversely affect your heart health, unsaturated fats—monounsaturated fatty acids (MUFAs) and polyunsaturated fatty acids (PUFAs)—have a beneficial effect. MUFAs—found in olive and canola oils, avocados, seeds like chia and flaxseed, and many nuts and nut butters—help maintain a healthy cholesterol balance and are part of healthy eating patterns like the Mediterranean and DASH diets, which have been shown to reduce the risk of heart disease.

PUFAs include omega-3 and omega-6 fatty acids, which your body can’t produce on its own but needs for good heart and brain function and overall health. Good sources of omega-6s include several vegetable oils (corn, soybean, safflower, and sunflower), most nuts, and sunflower seeds.

The main omega-3s—eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)—are abundant in fatty fish. Omega-3s help reduce triglycerides, and some studies suggest they may protect against abnormal heart rhythms, or arrhythmias.

Fatty fish are the best source of omega-3s, but you also can get them from plant sources. Flax and chia seeds, as well as canola and soybean oils, are good sources of alpha-linolenic acid (ALA), an essential omega-3 fatty acid that your body can convert to EPA and DHA, although only a small proportion of ALA is converted.

Nevertheless, these ALA foods are generally healthy options and are easy to incorporate into your diet. Simply sprinkle flax or chia seeds on your cereal or low-fat yogurt and use canola or soybean oils when you prepare salad dressings.

MUFAs and PUFAs are perhaps most beneficial when used to replace saturated or trans fats. However, even these healthy fats should be consumed in moderation. Each gram of fat contains 9 calories, compared with 4 calories for every gram of carbohydrate or protein, so eating too much of any fat can promote weight gain.

The Dietary Guidelines for Americans recommends that your total fat consumption should not exceed 20 to 35 percent of your daily calorie intake—about 44 to 78 grams of total fat for a 2,000-calorie-per-day diet—and most of that total should be unsaturated fat.

For more information on steps you can take to lower your cholesterol, purchase Managing Your Cholesterol from

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UHN Staff

University Health News is produced by the award-winning editors and authors of Belvoir Media Group’s Health & Wellness Division. Headquartered in Norwalk, Conn., with editorial offices in Florida, Cleveland, Pittsburgh, … Read More

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