Monounsaturated Fat Versus Polyunsaturated Fat

Most health professionals recommend that we include more unsaturated fats than saturated foods in our daily diet. In terms of unsaturated fats, the choices are either monounsaturated or polyunsaturated fats. Here is how they compare to each other in terms of chemical structure, typical food sources and health benefits.

Monounsaturated Fat

A monounsaturated fat has a single double bond in the fatty acid carbon chain. The remaining carbon atoms in the chain are linked by a single bond. The designation "unsaturated" means that the fat molecules contain less than the maximum amount of hydrogen atoms because of the double bonds. Monounsaturated fats are liquid at room temperature and semi-solid or solid when chilled. They have a higher melting point than polyunsaturated fats and a lower melting point than saturated fats.

Polyunsaturated Fat

A polyunsaturated fat has two or more double bonds between carbon atoms in the fatty acid chain. Like monounsaturated fats, they are solid at room temperature and thicken when chilled. They have a lower melting point than monounsaturated fats. Some polyunsaturated fats are omega-3 and omega-6 fatty acids, essential fatty acids that our bodies cannot produce but are vital for normal metabolism. Such fats must be acquired through diet.

Food Sources

Monounsaturated fats are found in a variety of fruits, nuts, and vegetables. Common food sources include avocados, olives, canola oil, corn oil, grapeseed oil, peanut oil, safflower oil, sesame oil, almonds, cashews, macadamia nuts, peanuts, hazelnuts, and pecans. They can also be found in animal products such as cod, red meat and whole milk. For example, beef fat is about 50% unsaturated fat.

Polyunsaturated fats are primarily found in fatty fish, nuts, and seeds, but also in algae, leafy greens, and krill. Plant-based food sources include pumpkin seeds, safflower oil, sunflower seeds, sunflower oil, corn oil, soybeans, soy oil, soy milk, cottonseed oil, hazelnuts and walnuts. Good fatty fish sources herring, mackerel, salmon, trout, and tuna.

Health Considerations

Compared to saturated fats and trans fats, monounsaturated and polyunsaturated fats are both considered "good" fats from a dietary health perspective because they are good for your heart, cholesterol levels, and overall health. They may also decrease the risk of type 2 diabetes. Polyunsaturated fats appear to have a health advantage over monounsaturated fats, especially those that are rich in omega-3 fatty acids (commonly found in fatty fish). These compounds reduce the risk of coronary artery disease and may also protect against irregular heartbeats and help lower blood pressure levels.

Shelf Life

Both types of fat turn rancid much quicker than saturated fats although monounsaturated fat will last longer than polyunsaturated fat. Most oils that are high in unsaturated fats - mono or poly unsaturated - will typically spoil within several weeks at room temperature. They will turn rancid even faster if cooked.