Polyunsaturated fats are essential fats the body can’t make and needs to obtain from the diet. They are usually in liquid form at room temperature or when refrigerated.
The two main categories of polyunsaturated fats found in foods are omega-6 fats and omega-3 fats.
Omega-6 fats provide readily available energy to the body as well as essential fats the body needs but cannot create. Three main types of omega-6 fats are found in foods: linoleic acid (LA), arachidonic acid (AA), and conjugated linoleic acid (CLA).
Linoleic acid is the key source of polyunsaturated fats in the diet and is found in the food supply in sunflower, safflower, corn, cottonseed, and soybean oils. Arachidonic acid is found in small amounts in meats, poultry, and egg yolk, and conjugated linoleic acid is found in butterfat and meat.
Omega-3 fats also provide our bodies with energy and essential fats. They’re also linked with heart health and other benefits.
Three different types of omega-3 fats are found in foods: eicosapentaenoic acid (EPA) and docosapaentanoic acid (DHA) are long-chain omega-3 fats found in fish, and alpha-linolenic acid (ALA) is a short-chain fatty acid found in plant foods. Here are some common food sources of each:
• EPA and DHA: Cold-water fatty fish such as salmon, tuna, trout, mackerel, herring, and oysters
• ALA: Soybean oil, canola oil, flaxseed oil, flaxseeds, walnuts, and tofu
In the body, very small amounts of ALA can be converted to EPA and DHA. Several foods and beverages, including ready-to-eat cereals and dairy foods, are also fortified with EPA, DHA, and/or ALA, although the amounts contained in such products are often small.
Foods rich in polyunsaturated fats provide energy to the diet. Many foods rich in polyunsaturated fats also provide other key nutrients. For example, vegetable oils are good sources of vitamin E, and fish and shellfish are rich in high-quality protein and the following vitamins and minerals:
• Vitamin D – Salmon, mackerel, sardines, and tuna (canned)
• Potassium – Halibut, haddock, salmon (sockeye), and clams
• Iron – Clams, oysters, and sardines
• Magnesium – Halibut and Pollock
• Calcium – Sardines, pink salmon, ocean perch (Atlantic), blue crab, clam, and rainbow trout
Several studies show that replacing saturate fats with foods rich in polyunsaturated and monounsaturated fats without increasing total calories can lower bad LDL cholesterol levels and help prevent heart disease and stroke.
Omega-3 fats have been found to confer some important health benefits. EPA and DHA, the omega-3 fats found in fish, support important functions in the brain, blood vessels, and the immune system. Studies suggest that EPA and DHA might reduce the risk of cardiovascular disease, diabetes, and prostate cancer. There’s evidence that consuming about 1 gram of EPA or DHA from supplements or fish can decrease the risk of death from cardiac events in people who have heart disease.
EPA and DHA can also protect your eyes from macular degeneration, support visual and neurological development in infants (the omega-6 fat arachidonic acid is also believed to play a role in this), and protect against preterm birth.
Some countries recommend lowering intakes of linoleic acid (an omega 6 fat) because they believe that high intakes can negate the benefits of EPA and DHA and increase the risk of inflammatory, immune, or other disease and conditions. Americans currently consume more than 10 times as much omega-6 fats as omega-3 fats. Although no expert recommendation to reduce linoleic acid has been made in the United States, it’s prudent to follow the healthy eating guidelines as outlined by MyPyramid, and to increase omega-3 fats by consuming more fish to boost nutrient intake and improve the overall quality of the diet. As with all fat (no matter what types of fatty acids they contain), too much can contribute to excess calorie intake and increase the risk for obesity or being overweight and related diseases and conditions.
Macular degeneration is the progressive deterioration of the macula (the back part of the retina) that can cause blindness.
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