Not so long ago, fat was the mortal enemy in the fight for good health. All fat was considered bad, especially for cardiovascular health. Today, the situation is more nuanced. Science has determined that all fats are not created equal.
In fact, some types of fat actually promote better health – even heart health. “There are good fats and bad fats,” says Sandra Arévalo, the director of community and patient education at Montefiore Nyack Hospital and a certified diabetes educator. Good fats help keep blood vessels and arteries smooth and flexible, she says. Bad fats stick to the walls of arteries and veins, causing clots that narrow the pathways blood follows in the circulatory system, a condition known as atherosclerosis.
It’s important to know the difference between good and bad fats, in large part because cardiovascular disease is the leading global cause of death, accounting for 17.3 million deaths per year. The American Heart Association presidential advisory on dietary fats and cardiovascular disease recommends lowering the intake of dietary saturated fat – one of the bad kinds – and replacing it with polyunsaturated vegetable oil – a good kind. According to the AHA, this substitution can reduce cardiovascular disease risk by about 30%, similar to the reduction achieved by statin treatment.
Good Fat vs. Bad Fat
There are many different types of fat. Your body makes its own fat from extra calories, and fat comes in foods you eat. Fat is essential to your health. It is “a major source of energy,” Arévalo says. “Fats help you absorb some vitamins and minerals, and they help build cell membranes and the sheaths surrounding nerves. They are essential for blood clotting and muscle movement.”
But some types of dietary fat play a role in cardiovascular disease, and all fats are high in calories and can contribute to weight gain. They also are a source of inflammation.
The evidence suggests it is smart to select healthier fats and avoid the less healthy ones. But how do you choose?
“An easy way to separate good from bad fats is looking at their consistency. Bad fats like lard are solid at room temperature, while good fats like olive oil are liquid,” Arévalo says. The solid, bad fats come in two main types:
- Saturated fat. This comes mainly from animal sources of food, such as red meat, poultry and full-fat dairy products like butter. Saturated fats raise total cholesterol and low-density lipoprotein cholesterol levels, which may increase your risk of cardiovascular disease. (LDL cholesterol is often called “bad” cholesterol.)
- Trans fat. Most trans fats are man-made from oils in a process called partial hydrogenation. Partially hydrogenated trans fats can boost total blood cholesterol, LDL cholesterol and triglyceride levels while also lowering high-density lipoprotein cholesterol, all of which can increase your risk of cardiovascular disease. (HDL cholesterol is sometimes called “good” cholesterol.)
Good types of dietary fat are primarily unsaturated fats:
- Monounsaturated fatty acids. These are found in many types of foods and oils. Eating foods rich in monounsaturated fatty acids instead of saturated fats has been shown to improve cholesterol levels, which can decrease your risk of heart disease and also of type 2 diabetes.
- Polyunsaturated fatty acids. Found mostly in plant-based foods and oils, these fats also improves blood cholesterol levels.
- Omega-3 fatty acids. Omega-3 is a type of polyunsaturated fat that appears to be especially beneficial for heart health. These fats help reduce chronic inflammation, which can lead to or progressively worsen heart disease, says Wesley McWhorter, a registered dietician, doctor of public health and director of culinary nutrition for the Nourish Program at the University of Texas School of Public Health. Omega-3, found in abundance in fatty fish like salmon, tuna, trout, mackerel, sardines and herring, and also in some plant sources like flaxseed, vegetable oils (canola, flaxseed, soybean) and nuts and other seeds, may decrease the risk of coronary artery disease.
How Much Fat Is OK?
The 2015-2020 Dietary Guidelines for Americans, from the U.S. Department of Agriculture and the U.S Department of Health and Human Services, recommend the following targets for healthy adults:
- Total fat: 20% to 35% of daily calories.
- Saturated fat: 10% or less of daily calories.
This means that if you eat 2,000 calories per day, 400 to 700 calories should come from fat, Arévalo says. “That translates into 45 to 75 grams of fat per day, of which only 4.5 to 7.5 grams should come from saturated fat.”
The guidelines also recommend that you avoid trans fat and replace saturated fat with healthier monounsaturated and polyunsaturated fats.
The Mayo Clinic offers these tips to eat healthier fats:
- Avoid trans fat. Check food labels for the amount of trans fat or partially hydrogenated fat listed.
- Use oil instead of solid fats. For example, you should sauté with olive oil instead of butter, and use canola oil when baking.
- Eat fatty fish. This includes eating salmon and mackerel, instead of meat at least twice a week to get healthy omega-3 fatty acids. Bake or broil seafood rather than frying it.
- Choose lean meat and skinless poultry. You should also trim visible fat and skin from meat and poultry.
- Snack wisely. Many processed snack foods are high in fat, especially solid fats. Be sure to check food labels for saturated and trans fats. Even better, pick whole fruits and vegetables to snack on.
- Don’t get bogged down in the details. Most foods contain different kinds and amounts of fat. Choose foods that contain unsaturated fats instead of those that contain saturated or trans fats. For example, canola oil contains some saturated fat but is mostly a monounsaturated fat. Butter, on the other hand, contains some unsaturated fat but is mostly a saturated fat.
“It’s about dietary patterns,” says McWhorter, a spokesperson for the Academy of Nutrition and Dietetics. “If you have wonderful oils but also eat lots of highly processed foods, what good is it?” Most of us don’t count calories or grams of fats. Instead, when you have a plate of food, look carefully at what it is made up of. “Does it have good vegetables on it, what oil is it cooked with? Your main focus is looking at your diet holistically,” McWhorter says.
