An important source of energy, fat is part of each cell in the body, making it necessary for life itself.
Too much of this nutrient, though, can lead to obesity and related health problems. The wrong kinds—especially saturated (largely from animals) and trans (manufactured) fats—can cause artery-clogging levels of LDL (lousy) cholesterol. These not-so-healthy fats remain fairly solid at room temperature and harden when refrigerated.
Other types of fat—mostly soft or liquid at room temperature—help to support HDL (healthy) cholesterol, fight chronic inflammation, and nourish the brain and eyes. Found in sea creatures and plants, these essential fatty acids (EFAs) are well worth exploring.
A Healthy Balance
EFAs consist of omega-3 and omega-6 fatty acids. Throughout most of history, humans have consumed a healthy balance of these—approximately twice as many omega 6s as omega 3s.
But with all the processed foods made with omega 6s in the United States today, that ratio has shifted to 17 to 1. “Major dietary studies have shown that when people are fed diets that lower this ratio, their death rates from heart disease fall significantly,” notes Artemis Simopoulos, MD, author of The Omega Diet. “If you have too many omega 6s, you can’t use omega 3s as efficiently.”
Omega 3s are anti-inflammatory, while “omega-6 fatty acids give rise to both pro-inflammatory compounds and anti-inflammatory compounds,” adds William S. Harris, PhD, director of the Metabolism and Nutrition Research Center of the University of South Dakota, Sanford School of Medicine.
Most experts recommend a Mediterranean diet, high in plant foods and omega-3-rich fish but low in saturated, trans, and omega-6 fats. Research finds this style of eating combats not only cardiovascular disease but also cancer, diabetes, and obesity.
Ready for an Oil Change?
Monounsaturated and polyunsaturated oils help improve cholesterol levels. Olive oil (a staple of the Mediterranean diet), almond, avocado, canola, hazelnut, peanut, and high-oleic safflower and sunflower oils are high in monounsaturated fats. Polyunsaturated oils include corn, flaxseed, pumpkin seed, soy, and walnut oil.
Besides fighting cardiovascular disease, omega 3-rich polyunsaturates appear to protect against rheumatoid arthritis and inflammatory bowel disease, while benefitting learning in children and psychiatric and neurodegenerative illnesses in adults.
To boost omega 3s, choose flaxseed, pumpkin seed, or chia oils. Of these, flaxseed oil has the highest omega-3 to omega-6 ratio (5:1).
Like fish oil, walnut oil has been found in randomized, controlled research to lower both LDL and total cholesterol, while decreasing triglycerides and raising HDL cholesterol. Polyunsaturated walnut oil has 10 percent omega-3 fatty acids.
Also consider hempseed oil, the only EFA with the ideal ratio of omega 6 to 3. Dark green in color with a smooth creamy texture and mild nutty flavor, hemp oil is excellent in salad dressings.
Pay attention to how culinary oils are produced, as some processes can remove nutrients or add unwanted substances.
Oils are extracted from plants by either pressing or refining. The traditional method for extracting the world’s earliest cooking oil (olive oil), stone pressing generates little heat and helps protect natural antioxidants. Hydraulic pressing, which extracts up to 70 percent of a plant’s oil, is typically used to produce extra-virgin olive oil, as well as avocado and walnut oils. Mechanical (or expeller) pressing applies no external heat, although the friction created in this process can raise the oil’s temperature. By contrast, cold pressing extracts oils at temperatures below 122°, making it best for borage, flaxseed, and wheat germ oils that are easily damaged by heat.
After extraction, oil can be further processed, or refined, to neutralize flavor or make it more stable, or less likely to oxidize and form free radicals. “Long-term use of oxidized fats can increase risk of arterial damage, cancer, inflammation, and premature aging of cells and tissues,” writes Margaret M. Wittenberg in New Good Food. While refining doesn’t affect EFAs, this added process can remove many antioxidants like vitamin E.
In the Kitchen
Smoke point, the maximum temperature to which oil can be heated before it starts to discolor and becomes damaged, varies greatly from one type of oil to another. “When oil begins to smoke, it releases carcinogens into the air and creates free radicals,” Wittenberg says. “These highly reactive molecules can cause cellular damage and breakdown,” leading to disease.
In general, you can use unrefined oils for recipes that call for low to moderate temperatures: baking at 320° or less, drizzling over cooked veggies or grains, mixing in salad dressings, light sauteing at 350°, and steaming.
Wittenberg recommends refined oils for higher-temperature baking, grilling, popping corn, sautéing over high heat, and stir-frying.
Refrigerating oils lengthens their lifespan. “When refrigerated, unrefined oils may keep for up to 14 months,” says Wittenberg, while refined oils may last up to 20 months.
Cold-pressed nutritive oils and those high in omega-rich polyunsaturates require refrigeration once they’re opened. Oils high in saturated fats, like coconut oil, are the exception, remaining stable at room temperature for as long as two years.
Monounsaturates like olive oil that you use frequently will last up to two months at room temperature (below 77°).
Because light can also cause oxidative stress, culinary oils benefit from packaging in opaque, nonreactive containers, or place clear containers in a dark pantry or fridge.