A stroll down the cooking oil aisle of your local supermarket may leave you shaking your head. So many choices… olive, corn, canola, safflower. The list seems to go on and on. Which do you choose?
Before answering that question, it helps to know a bit about cooking oils in the first place.
Fats and oils are made up of "building blocks" called fatty acids. Each type of fat or oil is a mixture of different fatty acids:
- Saturated fatty acids are found primarily in animal sources such as meat and poultry, whole or reduced-fat milk, and butter. Some vegetable oils like coconut, palm kernel oil, and palm oil have saturated fats. Saturated fats are usually solid at room temperature.
- Monounsaturated fatty acids are usually found in vegetable oils such as canola, olive, and peanut oils. They are liquid at room temperature.
- Polyunsaturated fatty acids are found mainly in vegetable oils such as safflower, sunflower, corn, flaxseed, and canola oils. Polyunsaturated fats are also the main fats in seafood. They are liquid or soft solids at room temperature. Specific polyunsaturated fatty acids, such as linoleic acid and alpha-linolenic acid, are called essential fatty acids. They are necessary for cell structure and making hormones. The body does not manufacture its own essential fatty acids; they must be obtained from the foods we eat.
- Trans fatty acids are formed when vegetable oils are processed into margarine or shortening. Sources of trans fats in the diet include snack foods and baked goods made with partially hydrogenated vegetable oil or vegetable shortening. Trans fatty acids also occur naturally in some animal products such as dairy products.
Eating foods high in monounsaturated fatty acids, on the other hand, may help lower LDL cholesterol levels and decrease risk of heart disease. Eating polyunsaturated fats in place of saturated fats decreases LDL cholesterol levels.
While we should do what we can do stay away from saturated fats and trans fatty acids, taking in a combination of monounsaturated and polyunsaturated fats keeps us nutritionally balanced, says K.C. Hayes, professor of biology at Brandeis University.
Fats and oils actually play an important role in how our body works, adds Cindy Moore, MS, RD, director of nutrition therapy for the Cleveland Clinic and spokeswoman for the American Dietetic Association. "Fats and oils provide a concentrated source of energy for the body. Fats are used to store energy in the body, insulate body tissues, and transport fat-soluble vitamins -- A, E, D, and K -- through the blood. They also enhance the taste, aroma, and texture of food, and contribute to a feeling of satiety, or fullness."
Choose Oil Wisely
When choosing which oil to use, take two things into consideration -- food preparation and health, says Mark Kantor, PhD, associate professor in the department of nutrition and food science at the University of Maryland.
The dietary oils you're most likely to see on your grocery shelves are:
Certain fats and oils work better in certain recipes, says Kantor, also a food oil expert with the Institute of Food Technologists. So if a recipe specifically calls for a particular type of oil, chances are that's the one you should use. If, however, you're choosing an oil for everyday meal preparation -- to make a salad dressing, for example, or sauté a chicken cutlet, Kantor recommends either canola or olive oil.
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Both canola (the name is derived from the words Canadian and oil) and olive oil are high in monounsaturated fatty acids, Kantor says, while being relatively low in saturated fats.
Canola is a form of rapeseed that was specially bred in Canada by traditional plant breeding techniques to change the chemical composition of rapeseed. It has what is considered to be an almost ideal balance of omega-6 to omega-3 fatty acids, two essential fatty acids that are vital for health.
Olive oil has also received much attention in recent years for its protective qualities against heart disease and cancer. In study results published in The New England Journal of Medicine, for example, research conducted by the University of Athens Medical School and Harvard School of Public Health found that among 22,000 Greeks, those who followed a Mediterranean diet, which is rich in olive oil, lowered their risk of death from heart disease by 33% and their cancer rate by 24% compared with volunteers who ate other foods.
Specialty oils -- such as sesame or walnut - may lend an interesting flavor to your food, but are generally pricey, difficult to keep fresh, and may not have as many uses as canola or olive oils, says Susan Nitzke, PhD, RD, professor of nutritional sciences at the University of Wisconsin-Madison.
Flaxseed oil, another specialty oil, is rich in omega-3 fatty acids and is being studied for its beneficial or preventive effects on illnesses ranging from cardiovascular disease to macular degeneration (a disease that causes blindness as we age), does not stand up to high temperatures, making it best used cold, perhaps mixed in a salad dressing. Both canola and olive oils, on the other hand, can be used either for salad dressings or for cooking. (No matter what oil you buy, Nitzke adds, buy only enough to use in a short period of time; no oil stays fresh indefinitely.)
While oils are necessary to keep your body operating at peak performance, as with most things, don't overdo. Since oils are 100% fat, says Cindy Moore, unless you're not getting any other fat in your diet (and that's pretty unlikely), then you need to watch how much extra fat you're adding with oils. "There are certain beneficial components to oils, but a little goes a long way," says Moore, who advises limiting added oils by one to two tablespoons a day.
Oil for Health
It may soon be possible to use cooking oil without having to watch your calories or your cholesterol quite so much. At Montreal's McGill University, researcher Peter Jones recently completed two studies on a new blend of cooking oil that enables people to rev up their metabolism, lower their cholesterol, and in some cases, lose weight.
The oil that Jones and his team tested -- for the moment labeled Functional Oil -- was composed of 65% tropical oils, 12% olive oil, 7% canola oil, 7% flaxseed oil, 6% coconut oil, and 3% phytosterols (plant extracts). According to Jones, the male participants in two clinical trials lost an average of one pound over a month; female participants did not lose weight but did experience a faster metabolic rate. Both men and women were found to have significantly lower cholesterol levels as well -- more than 13% lower, compared with olive oil, which is said to reduce cholesterol levels by 4.5%.
Already on the market (but only in Chicago and Atlanta or online) is Enova, a cooking and salad oil originally developed in Japan and now being sold in the U.S.
The makers of Enova say it can be used in place of conventional oils for baking, sautéing, frying, and in salad dressings and marinades. It's made from soy and canola oils that have been processed to contain a higher concentration of diacylglycerols, which have been shown to have numerous health benefits, including reducing post-meal blood triglyceride levels and enhancing weight loss when compared with traditional oils.
In a study published in the American Journal of Clinical Nutrition, health experts at Maastricht University in the Netherlands reported new results from tests conducted in which Enova was substituted for regular vegetable oil in the diets of healthy women. With the Enova oil diet, there was a significant increase after only one day in the oxidation or burning of fat, and after the second day a significant decrease in the desire to eat. The researchers associated these benefits with the difference in composition between Enova, comprised mostly of diglycerides, and regular vegetable oils, the majority of which is triglycerides.