Polyunsaturated Fat vs. Monounsaturated Fat: What's the Difference?

Polyunsaturated fat (PUFA) and monounsaturated fat (MUFA) are both types of healthy fats that, among other things, promote good cholesterol levels and offer other heart-health benefits. The difference between them starts on a molecular level.

Polyunsaturated fats have more than one carbon bond in their structure, known as a double bond, while monounsaturated fats have a single carbon bond. The body makes monounsaturated fats and gets them from your diet (e.g., avocado, olive oil). Polyunsaturated fats, on the other hand, can't be made by the body—they only come from foods (e.g., fish and nuts).

This article discusses the two types of unsaturated fats, including why they’re good for you, what foods have them, and how they differ from saturated fats.

What Are Unsaturated Fats?

Unsaturated fats are considered healthy fats. Research has found that including them in your diet can improve cholesterol, decrease inflammation, and stabilize heart rhythms.

These fatty acids are made of carbon atom chains that contain one or more double bonds, which reduces the amount of hydrogen atoms attached to the chain. Because of their structure, they’re usually liquid at room temperature.

In contrast, saturated fats are “saturated” with hydrogen atoms, meaning they have the maximum amount of hydrogen surrounding the carbon atoms. Saturated fats are typically solid at room temperature.

Saturated fats have long been thought to increase your risk of cardiovascular disease because they increase bad cholesterol (low-density lipoprotein, or LDL). However, research is showing that the link between saturated fat and cardiovascular disease may not be as clear as once thought. Conflicting research findings leave us with insufficient evidence that saturated fat by itself increases the risk of heart disease.

While research is still ongoing, the American Heart Association (AHA) recommends eating foods with unsaturated fat instead of saturated fat when possible. That’s because research has found that replacing saturated fats with unsaturated fats can decrease the risk of heart disease. In contrast, replacing saturated fat with refined carbohydrates did not show the same reduction in heart disease risk, and in some cases made it worse.

According to the AHA, both monounsaturated and polyunsaturated fats can lower rates of cardiovascular disease and all-cause mortality. These fats also help to decrease bad cholesterol and triglyceride levels, both of which contribute to heart disease.

Monounsaturated Fats

Monounsaturated fats have only one carbon-to-carbon double bond in their molecular structure. They help lower bad (LDL) cholesterol levels and help maintain the overall health of cells. 

Several healthy foods contain monounsaturated fats, including:

• Cooking oils, such as olive oil, sesame oil, and canola oil
• Peanut butter
• Nuts, including peanuts and cashews
• Avocados
• Olives
• Sesame seeds
• Healthy spreads labeled “high oleic”

Polyunsaturated Fats

Polyunsaturated fats have more than one double bond in their carbon structure. Much like monounsaturated fats, polyunsaturated fats can also help lower unhealthy LDL cholesterol. 

Polyunsaturated fats are essential for your body’s functions and play a role in building cell membranes and blood clotting. Your body can’t make polyunsaturated fats, so you have to get them from food.

There are two main types of polyunsaturated fats: omega-3 and omega-6 fatty acids. Your body needs both of these for brain function and cell growth.

Foods high in polyunsaturated fats include:

• Sunflower seeds and flaxseeds
• Cooking oils, including corn oil, safflower oil, and soybean oil
• Nuts, such as walnuts, pine nuts, and Brazil nuts
• Fatty fish, such as salmon, mackerel, herring, albacore tuna, and trout

Omega-3 Fats

Omega-3 fatty acids, a type of polyunsaturated fat, have been extensively studied regarding their effects on heart health.

Research shows omega-3 fats can lower triglyceride levels and slightly increase HDL (good cholesterol) levels. A 2016 study found eating fish high in omega-3 fatty acids at least twice a week significantly decreases blood triglyceride levels.

The following foods contain this specific type of polyunsaturated fat:

• Fatty fish, including salmon, mackerel, herring, sardines, and tuna
• Seeds, including flaxseed and chia seeds
• Walnuts
• Algae (e.g., seaweed, spirulina, nori)

The American Heart Association recommends eating at least two 3.5-ounce servings of non-fried fish every week to get the benefits of omega-3 fats.

Summary

You may tend to think of fats as being bad for you. However, your body needs some of the fat that we get from food, particularly healthy fats like unsaturated fats. While the jury is still out on saturated fats, most doctors still recommend replacing them with unsaturated fats when possible.

Both monounsaturated fats and polyunsaturated fats have heart-healthy benefits, including decreasing inflammation and improving cholesterol. Both offer health benefits and they’ve been found to decrease cardiovascular disease when they replace saturated fat in your diet.

Your physician or registered dietitian can help answer your questions about the types of fats to include in your diet.