Best food groups: Nuts and seeds, and their oils
Also consider: Pecans, Brazil nuts, sesame oil, pumpkin seeds
What is polyunsaturated fat and why is it so important? Polyunsaturated fatty acids, or PUFA for short, contain at least two double bonds (poly) on its fatty-acid carbon chain. PUFAs are essential fatty acids (meaning our body can't make them), and include omega-3 fatty acids (EPA, DHA, ALA) and omega-6 fatty acids (linoleic acid). You'd probably know one if you saw one, as polyunsaturated fats are typically liquid at room temperature and even when they are refrigerated. One function of these in the body is to produce another type of fatty acid called arachidonic acid, which controls the signaling pathways that are responsible for regulating the body's warning system; namely, the inflammation response.
Did you know? PUFAs have been shown to reduce cholesterol levels, and in turn lower the risk for heart disease, when substituted for saturated fats.
How much is enough? As noted earlier, it is recommended to consume 25 to 35 percent of your calories from fat: no more than 10 percent of fat from saturated fat, with the rest split up evenly between polyunsaturated and monounsaturated fat. Polyunsaturated fats are pretty prevalent in the diet, so it is nearly impossible for someone of average health and appetite to be deficient in PUFAs. However, most health experts agree there is way too much omega-6 fatty acids and not enough omega-3s in the American diet.
A lot of literature on inflammation details the perils of overconsumption of omega-6s. These "diseases of civilization," which include type 2 diabetes, stroke, Alzheimer's disease, heart disease, and many others, have links to suboptimal distribution of healthy fats in our diet. That is, the high levels of omega-6s wouldn't be a problem if we consumed adequate levels of omega-3s to balance them out.
Supplements: Polyunsaturated fats are plentiful in the diet, but as mentioned earlier, most people would benefit from increasing their omega-3.
Did you know?
The number one highest source of polyunsaturated fat listed in the USDA reference 24 database is piecrust, due to its high fat content. It's great to know that Grandma's traditional lard crust has been replaced by healthier fats, but unless you have been living under a rock and didn't get the memo, piecrust is not considered a healthy food.
1. Walnuts and Walnut Oil
Walnuts are the richest source of omega-3s compared to any other nut, an excellent source of copper and manganese, and a good source of iron, magnesium, and phosphorus. Don't remove that skin. The skin contains about 90 percent of the nuts' phenols, which include phenolic acids, flavonoids, and tannins. Walnuts are also an excellent source of vitamin E, particularly a form called gamma-tocopherol, which a study showed may reduce the growth of colon cancer cells in vitro. Researchers from Penn State found that by adding a combination of walnut oil and walnuts to the diet reduced resting diastolic blood pressure even during times of stress.
The walnut is the oldest nut known to mankind, dating back to 7000 BC. English walnuts, which are the most commonly consumed walnut in America, were originally reserved only for the royal family in ancient Persia. English merchants transported the nuts for trade around the world, where they were referred to as "English walnuts," though they were never grown commercially in England. California produces most of the world's supply of walnuts.
2. Pine Nuts
Pine nuts are an excellent source of PUFAs, as well as other nutrients . . . . if you're not allergic to them . Moreover, the oil in pine nuts might be the best thing since paper napkins for controlling hunger: Researchers found that Korean pine nut oil stimulates two appetite-suppressant hormones called cholecystokinin and GLP-1. Women subjects who ingested the oil reported significantly suppressed appetite thirty minutes after ingestion!
3. Grapeseed Oil
Grapeseed oil has a smoke point of 420°F, making it an ideal cooking oil. Its high polyunsaturated content and clean, light taste allows it to be used as a salad dressing, mayonnaise substitute, or base in an infusion with a variety of spices. While this oil does contain 26 percent of one's daily dose of vitamin E, many of the polyphenols and antioxidants that are typically present are lost during the production process of most grapeseed oil products. In a study involving fifty-six participants, about 3 tablespoons of grapeseed oil was added to their daily diet. After three weeks, their HDL cholesterol levels rose by 4 points.
4. Sunflower Seeds and Oil
Refined sunflower oil's smoke point is 450°F, compared to its unrefined counterpart of 225°F, making the refined version perfect for deep-frying, and the unrefined great for dressings. There are a variety of forms of sunflower oil, varying in their polyunsaturated and monounsaturated fats, but all have low amounts of saturated fats. Traditional sunflower oil contains about 68 percent linoleic acid, whereas a newer hybrid version contains 60 percent oleic (a monounsaturated fat). Sunflower oil contains more vitamin E than any other vegetable oil, supplying nearly 40 percent of one's DV, not to mention it is the lowest in saturated fat. Out of three main types of sunflower oils, a variety called NuSun has the lowest concentration of saturated fat. A diet high in oleic sunflower oil and NuSun has been shown to improve an individual's cholesterol profile (boosting HDL cholesterol and lowering LDL), in addition to improving triglyceride levels.
5. Flaxseed Oil
Flaxseed oil, also referred to as linseed oil, contains both omega-3 and omega-6 fatty acids. This clear to yellowish liquid has numerous nonfood applications, such as in paint, wood finishes, and linoleum, and of course is also a nutritious food and dietary supplement. Flaxseed oil contains 26 percent of one's daily dose of vitamin E, which, as in walnuts, comes in the gamma-tocopherol form! Studies have found that fats in flax may reduce heart disease through several mechanisms, including making platelets less sticky, reducing inflammation, promoting blood vessel health, and reducing risk of arrhythmia, as well as having other health benefits.
6. Soybeans
Soy again makes the list, this time for being an excellent source of PUFAs . A Chinese study found that soybeans added to the diets of healthy volunteers improved immune and brain function.
7. Corn Oil
Besides being an excellent source of polyunsaturated fats, corn oil is also rich in plant phytosterols. Subjects who consumed commercial corn oil versus sterol-free corn oil had substantially lower cholesterol levels, which were attributed to the effects of phytosterols more than to the effects of the polyunsaturates in corn oil.
Source: USDA National Nutrient Database for Standard Reference, Release 24