Good Fats vs. Bad Fats: Everything You Should Know About Fats and Heart Health

The word “fat” often has a negative connotation, but the body actually needs certain healthy fats to function properly. For example, fats are necessary to construct cell membranes, insulate nerves, and ensure 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.”

There are numerous types of fat — some good for us and some not. Scientific research about the health risks and benefits of fats is constantly evolving. The current evidence and guidance suggest we should focus our diet around consuming healthy fats and avoiding unhealthy fats.

Types of Fats

Dietary fats fall into three categories:

• Unsaturated fats These good fats are the type of fat you should eat the most of as part of a heart-healthy diet. There are two types of unsaturated fats: monounsaturated and polyunsaturated. Pecans, hazelnuts, almonds, sesame seeds, pumpkin seeds, olive oil, peanut oil, and canola oil have high concentrations of monounsaturated fats. Fish, flaxseeds, flaxseed oil, corn oil, soybean oil, and sunflower oil contain polyunsaturated fats. Omega-3 fatty acids — found in some types of fish, such as salmon and herring, and in plant products, such as soybean oil, canola oil, walnuts, and flaxseed — are a type of polyunsaturated fat that is thought to be particularly good for the heart.
• Saturated fats Animals are the primary source of saturated fats, with high levels found in beef, pork, and full-fat dairy products and medium levels in poultry and eggs. Some vegetable oils, such as palm oil, also contain a lot of saturated fat.
  Saturated fats are necessary for the body — but in small amounts. The Dietary Guidelines for Americans recommend that less than 10 percent of your daily calories should 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 at most should come from saturated fat.
• Trans fats These are the fats you may want most but shouldn’t have. Most unsaturated fats are liquid at room temperature. To make them solid, food manufacturers add extra hydrogen, making it a “hydrogenated,” or trans, fat. The highest levels of trans fats are found in baked goods, animal products, and margarine.

Effects of Non-Healthy Fats on the Heart

Trans fats are the worst type of fats for the heart, blood vessels, and overall body health. Consuming trans fats:

• Raises bad LDL levels of cholesterol and lowers good HDL levels of 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 (FDA) banned the use of partially hydrogenated oils (PHOs), the primary source of artificial trans fats, from processed foods. This policy led to a near elimination of artificial trans fats in the U.S. food supply by 2018.

But trans fats are not completely gone from foods, as they occur naturally in small amounts in meats and dairy products, as well as some edible oils.

Eating a meal high in saturated fats — say a large steak with 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.

The effects of saturated fats on the body has been the source of some controversy in recent years, as a handful of studies have questioned just how harmful saturated fats are. For example, a meta-analysis published in the American Journal of Nutrition concluded: “There is insufficient evidence from prospective epidemiologic studies to conclude that dietary saturated fat is associated with an increased risk of CHD [coronary heart disease], stroke, or CVD [cardiovascular disease].”

A highly publicized study published in 2014 in the Annals of Internal Medicine determined that diets high in saturated fat do not raise the risk of heart disease.

But that controversial conclusion was met with criticism, and American nutritional guidelines still recommend limiting the amount of saturated fats consumed daily to no more than 10 percent of your daily calories. The American Heart Association takes it even further and suggests that saturated fat make up no more than 5 to 6 percent of your daily calories.

The overarching guidance is that limiting saturated fats and replacing them with good fats, especially polyunsaturated fats, is what 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.

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 your risk of cardiovascular disease.

A review published in June 2015 in Cochrane Database of Systematic Reviews 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.”

Eating Fish for a Healthy Heart

Fish is a heart-healthy source of dietary protein that is low in saturated fat and high in 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 ¾ cup of flaked fish. This can help reduce the risk of cardiovascular disease.

The AHA cautions that some fish types may be high in environmental pollutants such as mercury, and therefore recommends that children and pregnant women avoid fish types that are thought to have the highest mercury levels (king mackerel, swordfish, shark, tilefish). The AHA also recommends varying the kinds of fish you eat to minimize effects of these environmental contaminants.

But for post-menopausal women and middle-aged men, the benefits of eating fish far outweigh the risk, as long as you abide by the recommendations established by the FDA and the Environmental Protection Agency.

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 fat, and make sure most of the fat you eat is good fat from fish, nuts, and healthy oils.