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, 

Time to dig into some facts about fats. Fats play a crucial role by providing energy, facilitating cellular function, protecting organs, regulating temperature, absorbing nutrients, and producing hormones. There are different types of fats, and they can vary by chemical structure. As you noted, these different fat types typically fall into two categories, those that are considered "bad fat" and those that are considered "good fat". However, the differences between these kinds of fats are more complex than simply being "good" or "bad." Unsaturated fats—whether mono- or polyunsaturated—are often thought of as the most effective when it comes to supporting your health, and saturated or trans fats are typically what you want to reduce or avoid. The great news is that food nutrition labels can help you to take the guess work out of understanding what fats are commonly found in many of the foods you eat. Read on to learn more! 

To help you figure out the pros and cons of the different types of fats you consume, you may first be interested in understanding the difference between the types of cholesterol. This is because cholesterol—a type of fat naturally produced in the liver—is directly impacted by the different types of fats you consume through food. The body uses cholesterol to build cells and hormones. Cholesterol is carried through the blood on lipoproteins—another type of fat naturally produced in the body. These lipoproteins can be broken up into two kinds: low-density lipoproteins (LDL) and high-density lipoproteins (HDL). Too much LDL can cause plaque buildup on blood vessel walls which can increase the risk for heart disease and stroke. On the other hand, HDL can bring cholesterol back to the liver to be removed from the body, lowering the risk of heart disease and stroke. 

In addition to LDL and HDL, triglycerides are yet another form of naturally occurring fat that can change levels based on the types of fat a person consumes. Triglycerides are extra fat that the body stores when that fat isn't used immediately. The body often pulls on these triglyceride reserves to provide energy. Similar to LDL and HDL, some types of fats consumed through food can increase triglycerides, while others can lower them. 

Now that you have some background on naturally occurring fats, it will be easier to recognize how the different types of fat may be affecting your health. To begin, “good fats”, also known as unsaturated fats, are generally liquid at room temperature but can begin to solidify if they’re cooled. These fats can be broken down into two subtypes: 

  • Monounsaturated fat is found in olive, canola, and peanut oil, avocados, nuts, and seeds. Studies show that it improves cholesterol levels, which can then reduce heart disease risk. There’s also evidence that monounsaturated fats may prevent insulin resistance and help control blood sugar for those with type 2 diabetes. 
  • Polyunsaturated fats are differentiated from monounsaturated fat based on the chemical bonds in the fat. Two of the most common polyunsaturated fats are omega-3 and omega-6. Omega-3 fatty acids are a type of fat that the body can’t produce naturally. However, the body can use them to produce hormone-like substances that have anti-inflammatory properties. Sources of omega-3s can include fatty fish, flaxseeds, walnuts, and canola or soybean oil. Omega-6 fatty acids can be found in corn, soybean, cottonseed, sunflower, and safflower. Polyunsaturated fats can improve blood cholesterol levels, regulate blood sugar, reduce triglycerides, and regulate blood pressures. 

On the other hand, “bad fats” can be found in a variety of forms, but are still generally broken down into two types: 

  • Saturated fats are mainly found in meat products but can also be found in dairy products (i.e., milk, butter, cheese, dairy and grain-based desserts) and in certain oils (e.g., coconut, palm, and palm kernel). The American Heart Association recommends consuming less than ten percent each day, as too much saturated fat can increase LDL levels. 
  • Trans fats are created when hydrogen is added to vegetable oil. When this happens, it becomes solid at room temperature. It was discovered that trans fats raise LDL while lowering HDL, making these substances harmful for heart health. Because of this, the United States has banned the use of trans fats in food. Additionally, food manufacturing companies are 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 on the nutrition facts label. That means, even if the label reports no trans fats, words such as "partially hydrogenated" or "hydrogenated" in front of the word “oil” on the ingredients list can still indicate if any may be present. These fats are typically found in fried foods, baked goods, and margarine to name a few. 

When it comes to understanding nutrition labels, it can be important to note that the amount of unsaturated fats is sometimes listed in a separate line. However, it’s most commonly listed out as a separate line for both trans and saturated fats and it can be calculated by subtracting the two from the total fat. It may also be helpful to note that omega-3 and omega-6 fatty acids generally aren’t listed individually on the nutrition facts label. 

Here’s to hoping this information was helpful and can provide you with more insight into what you’re eating. This way you can make more informed choices about what types of fats you're consuming. 

Happy eating, 

Last updated Nov 24, 2023
Originally published Mar 22, 2002

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