A Guide to Good Fats vs. Bad Fats for Your Heart

For years, there have been heated debates about the relationship between the fat you eat and health, particularly cardiovascular health. One thing is clear — not all fats are created equally. This means that the kinds of fat you eat may matter more than the amount. 

Researchers have studied how dietary fats affect heart health by looking at the way they change cholesterol and triglycerides levels. So, first, let’s review what cholesterol levels mean for your health. In general, it’s best for your heart to have:

• Low levels of “bad” cholesterol, also known as low-density lipoprotein (LDL)

• High levels of “good” cholesterol, also known as high-density lipoprotein (HDL)

• A high ratio of good to bad cholesterol (because good cholesterol helps your body get rid of bad cholesterol)

• Low levels of triglycerides

Let’s go through the different types of fat in food, and how each one affects your health. We’ll also dive into how each type of fat affects different cholesterol levels. We've ordered the four main types of fat from most healthy to least healthy.

1. Polyunsaturated fats

Polyunsaturated fats (PUFAs) are generally heart healthy. Scientists believe that PUFAs act on the heart, blood vessels, and blood in different ways to achieve these healthy effects. There are two groups of PUFAs: 

• Omega-3 PUFAs: These are in oily fish, such as salmon, herring, mackerel, and trout. These fats are also in fish oil supplements. A certain type of omega-3 fat is also in plant foods, like walnuts, canola oil, soybean oil, hemp, chia, and flaxseed. 

• Omega-6 PUFAs: These are in safflower, sunflower, and corn oils. 

Research shows that omega-3 PUFAs can lower triglycerides, especially in people with higher triglyceride levels. Researchers aren't sure about the differences between consuming omega-3s as supplements versus whole foods. But most scientists agree that there’s benefit in eating 1 to 2 servings per week of seafood (as long as it’s not deep fried).  

Similar thinking applies to omega-6 PUFAs. There’s some concern that omega-6 PUFAs are broken down into a substance that can cause inflammation. Despite this, most research studies and reviews have shown that eating omega-6 PUFAs can help the heart.

There has also been debate about the ratio of omega-3 to omega-6 fats in a person’s diet. While many sources may suggest eating more omega-3 fats, a safe approach is to eat omega-3 and omega-6 fats in moderation to keep your heart healthy.

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2. Monounsaturated fats

There are two groups of monounsaturated fats:

• Plant-based monounsaturated fats: These heart-healthy fats can be found in olive oil, nuts, nut butters, and avocados. They protect against heart disease since they decrease bad cholesterol and triglycerides, but maintain or even increase good cholesterol.

• Animal-based monounsaturated fats: These fats come from red meat and dairy. Studies have shown that this type of fat is less protective for a person’s heart. This may be because these foods also contain saturated fat, which reverses the healthy effects. More research is needed to be sure.

But one thing seems clear: Eating PUFAs and/or monounsaturated fats from any source is better than eating only saturated and trans fats.

3. Saturated fats

Saturated fats are naturally present in animal products, including meat, butter, and cheese. But there are different families of saturated fats found in different foods. And they have different effects on cholesterol and triglyceride levels:

• Saturated fat in red meat (oleic, stearic, and palmitic acid) and dairy products like butter (palmitic acid) increase bad cholesterol.

• Saturated fats in plant sources, such as coconut oil (lauric acid), may improve the cholesterol ratio by lowering LDL and increasing HDL. But it’s still unclear if coconut oil should be recommended for heart health. The general recommendation is to use it sparingly if you have high cholesterol.

Many large studies haven’t found a link between how much total saturated fat people eat and their risk for heart disease. And there is a growing body of research that suggests that saturated fats have earned a worse reputation than they deserve.

Despite this, the American Heart Association recommends limiting saturated fat to no more than 5% to 6% of total daily calories. And the 2020-2025 Dietary Guidelines for Americans recommend keeping total saturated fats below 10% of total calories.

4. Trans fats

Trans fats are considered to be the most harmful for your health. They can be found naturally in some foods. But the main source of trans fats in foods is through the partial hydrogenation of saturated fats. This happens during the industrial processing of food. 

Trans fats (also called “partially hydrogenated oils” on nutrition labels) are commonly found in:

• Margarine spreads

• Fried foods like donuts

• French fries

• Mozzarella sticks 

• Industrially produced baked goods like cakes, biscuits, cookies, and crackers

Trans fats have harmful cardiovascular effects. They raise bad cholesterol and lower good cholesterol. Because of their extreme health risks, in 2018 the FDA declared trans fats to be unsafe, leading to their removal from the food supply.

Comparison of the 4 main types of fat

We just went through a lot of information. So here’s a summary of the four main types of fats, including their food sources and their effect on cholesterol, triglycerides, and heart health.

It’s important to remember that fat is an important part of a heart-healthy diet. A low-fat diet is not the solution to reducing cholesterol levels or protecting heart health. 

Studies have shown that very low-fat diets increase triglyceride levels and decrease good cholesterol. This increases the risk of heart disease. 

So it’s the type of fat that you eat and the other foods in your overall diet that play the biggest role in cholesterol levels and heart-disease risk.

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Written by:

Cherilyn Davis, MD

Cherilyn Davis, MD, is a board-certified pediatrician in NYC. She's held local and national roles at the American Medical Women's Association, including board member of the physician division and physician chair of social media.

Edited by:

Katie E. Golden, MD

Katie E. Golden, MD, is a board-certified emergency medicine physician and a medical editor at GoodRx.

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