Good Fats vs. Bad Fats: Everything You Should Know About Fats and Heart Health
One type of fat protects your heart, the other puts you at risk of cardiovascular disease. It’s wise to know the difference.
The word “fat” often has negative connotations, but the body needs certain healthy fats to function properly. For example, fats are necessary for constructing cell membranes, insulating nerves, and ensuring that many vitamins, including A, D, E, and K, work the way they should.
“For many years all fat was vilified and was limited as much as possible by most people looking to lose weight,” says Kelly Kennedy, RD, a registered dietitian at Everyday Health. “But this is absolutely not necessary, and limiting fat too much can even pose risks to human health. Fats are an essential part of a healthy diet, and there are several healthy choices.”
Read on to learn more about the different types of healthy and unhealthy fats.
Types of Fat
There are several types of fat. Some are good for us, and and some are not. Scientific research about the health risks and benefits of fats is constantly evolving. The current evidence and guidance suggest that we should focus our diet around consuming healthy fats and avoiding unhealthy ones.
Dietary fats fall into three categories:
Unsaturated Fats
Put simply, unsaturated fats are the good fats. You should eat unsaturated fats as part of a heart-healthy diet. There are two types of unsaturated fats: monounsaturated and polyunsaturated.
Monounsaturated fats can be found in many nuts, seeds and oils, including:
Polyunsaturated fats are crucial for heart health. They provide nutrients to help develop and maintain cells, and they help to reduce the levels of bad cholesterol in your blood. This can lower your risk of heart disease and stroke. Polyunsaturated fats include omega-3 and omega-6 fatty acids, which are essential nutrients your body can’t produce on its own.
Omega-3 fatty acids are particularly good for the heart. They are found in abundance in some types of fish, such as salmon and herring, and in plant products, such as soybean oil, canola oil, walnuts, and flaxseed.
Saturated Fats
Animal foods are the primary source of saturated fats, with the highest levels found in beef, pork, and full-fat dairy products. Saturated fats are necessary for the body, but in small amounts.
The Dietary Guidelines for Americans recommends that less than 10 percent of your daily calories come from saturated fats, preferably from lean poultry and low-fat or fat-free dairy products. For people who consume 2,000 calories per day, only 20 grams of fat at most should come from saturated fat.
Poultry (especially the skin) and eggs also contain a pretty high amount of saturated fat. Some vegetable oils, such as palm oil, are also high in saturated fat content.
Saturated fats include:
Sausages, burgers, bacon
Pork, beef
Poultry
Whole-fat dairy milk, butter, and cheese
Cookies, pastries, and cakes
Pizza
Trans Fats
Trans fats are the most dangerous for your heart health. They do exist naturally, but food manufacturers also make them as part of their manufacturing process. This is because most unsaturated fats are liquid at room temperature. To make them solid, food manufacturers add extra hydrogen, thereby making it a “hydrogenated,” or trans, fat. They are dangerous and can clog arteries, increasing the risk of heart attack and death.
Trans fats can be found in:
Fried goods
Baked goods
Processed snacks
How Do Unhealthy Fats Affect the Heart?
Trans fats are the worst type of fat for the heart, blood vessels, and overall body health. Consuming trans fats:
Raises levels of low-density lipoprotein (LDL, or “bad”) cholesterol and lowers levels of high-density lipoprotein (HDL, or “good”) cholesterol
Increases the risk of heart disease and stroke
Contributes to insulin resistance and is associated with a higher risk of type 2 diabetes
In 2015, the U.S. Food and Drug Administration banned the use of partially hydrogenated oils, the primary source of artificial trans fats, in processed foods. This policy led to a near elimination of artificial trans fats in the U.S. food supply by 2018. In 2023 the rules were finalized.
But trans fats are not completely gone from foods, as they occur naturally in small amounts in meats and dairy products, as well as in some edible oils.
Eating a meal high in saturated fats — say a large steak with a potato salad loaded with eggs and mayo — can drive up total cholesterol and tip the balance to more LDL, or “bad” cholesterol. This, in turn, can cause blood vessels to narrow and prompt blockages to form in the arteries. Saturated fats also cause triglycerides (made from excess calories and stored in fat cells) to go up. High triglyceride levels increase the risk of high blood pressure, diabetes, and heart problems.
That said, saturated fats remain a topic of debate. Some studies indicate that saturated fat may actually be beneficial for overall health, or at least not as harmful as scientists have generally believed. However, the overarching guidance remains that limiting saturated fats and replacing them with good fats, especially polyunsaturated fats, improves cholesterol and lowers the risk of heart disease.
“There are always going to be studies on both sides of an argument, however, the current body of research suggests that saturated fat is not good for human health,” Kennedy says.
What Is the Good Kind of Fat?
Unsaturated fats are the good kind, and the healthiest of these are polyunsaturated fats. Fish is a heart-healthy source of dietary protein that is low in saturated fat and high in polyunsaturated fats, such as omega-3 fatty acids. The American Heart Association recommends eating two servings of fish per week. A serving is equivalent to 3.5 ounces of cooked fish or about three-quarters of a cup of flaked fish. This can help reduce the risk of cardiovascular disease.
Polyunsaturated fats have several health benefits. They are essential nutrients that build cell membranes, aid in clotting and muscle movement, and help with inflammation. They are also used to build the covering of nerves.
The bottom line is that you need healthy fat in your diet, and it does matter what kind of fat you eat. For cardiovascular health, limit your intake of saturated fat, avoid trans fats, and make sure most of the fat you eat is good fat from fish, nuts, and healthy oils.
Replacing Bad Fats With Good Fats
Replacing some saturated fat from animal sources with healthy fat from plant sources can reduce LDL and triglyceride levels and lower your risk of cardiovascular disease. A review study found that replacing saturated fats with polyunsaturated fats can lower your risk of heart disease.
Kennedy says there are easy ways to make these swaps. “For example, instead of cooking your food in butter, opt for olive oil instead,” she recommends. “Top a salad or sandwich with fresh avocado instead of bacon or cheese. Or choose peanut or almond butter to top whole-grain toast or a whole-wheat bagel, in place of butter or cream cheese.”
The Takeaway
Some fats are bad for your health, while others are good for it — and especially your heart. In general, try to limit or avoid trans fats and saturated fats from foods such as sausages, burgers, and other animal meats, while also ensuring that you eat plenty of healthy unsaturated fats. Some good sources include nuts, seeds, and fish. Healthy fats can help lower bad cholesterol levels and reduce the risk of heart disease. If you’re concerned about your heart health or want to learn more, talk to your doctor or a dietitian.
