What Is Polyunsaturated Fat?

What It Is, Where It's Found, What it Does in Your Body

There are two main types of fats: saturated and unsaturated fats. What distinguishes them is their chemical structure.

Saturated fats have no double bonds in their chemical structure and are "saturated" with hydrogen atoms. Unsaturated fats, on the other hand have double bonds. Monounsaturated fats have just one double bond. Polyunsaturated fats have more than one of these bonds.

Those double bonds make the fat bendable, which is why polyunsaturated fats are liquid at room temperature and even in the refrigerator (saturated fats, on the other hand, are typically solid at room temperature).

The Two Types of Polyunsaturated Fats

There are two main types of polyunsaturated fatsomega-3 fats and omega-6 fats. Both of these types of fat are essential fatty acids, meaning the body cannot manufacture them and they must be taken in through diet.

Omega-3 fatty acids are found in oily fish (such as salmon and trout), nuts and seeds. Omega-3 fatty acids are thought to protect against heart disease, inflammation, certain types of cancer, diabetes, Alzheimer’s disease, and macular degeneration (a leading cause of vision loss).

Omega-6 fatty acids are found in nuts, seeds and vegetable oils, such as soybean, cottonseed, corn, sunflower, and safflower oil.

The ratio of omega-3s to omega-6 is important for health, with too much omega-6 in relation to omega-3s thought to lead to inflammation (which is at the core of chronic diseases, such as heart disease and diabetes).

What Polyunsaturated Fats Do for Your Health?

Replacing saturated fats with polyunsaturated fats can help reduce your "bad" LDL cholesterol levels, which in turn can lower your risk for heart disease.

An example would be to cook a fillet of fish in a bit of safflower oil rather than butter.

Oils that are high in polyunsaturated fats also are richin vitamin E, an important antioxidant.

The Problem with Polyunsaturated Fats

Although polyunsaturated fats are generally thought of as healthy, there are at least two possible exceptions to this statement.

One is that there is some evidence that polyunsaturated fat, in excess, can contribute to cancer risk. It is thought that the reason for this may be that polyunsaturated fats turn rancid more quickly than other fats. Therefore, it's recommended you properly store oils with high amounts of polyunsaturated fats. Store them in a cool, dark place before opening, and in the refrigerator after opening.

The other potential issue with polyunsaturated fats is that of the two main types of polyunsaturated fat, the amount of omega-6 fat that we tend to consume has increased dramatically in recent decades, while in general the amount of omega-3 fat we consume is lower. Some experts feel that this imbalance is contributing to inflammation in our bodies, and increasing the risk of such chronic diseases as arthritis, diabetes, and heart disease.

Foods That Are High in Polyunsaturated Fat

The biggest sources of polyunsaturated fats are found in various oils, including corn oil, soy oil, regular safflower and sunflower oils (i.e., not "high oleic" oil) and cottonseed oil.

Flaxseed oil is high in omega-3 fats. Other foods that have good amounts of polyunsaturated fats are seeds and nuts, oily fish, and foods made with oil, such as mayonnaise and salad dressing.

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