You’re in the kitchen about to saute red peppers and pea pods for a stir fry and you need to choose an oil, but which one? Olive oil? Canola oil? What about coconut oil?
The options are endless, but which is the healthiest? Maybe you shouldn’t be adding oil at all? Don’t Americans eat too much fat anyway? Are tropical oils really better than vegetable oils? Why is this so confusing?
Low-fat diets have been recommended and followed since the 1980s, but in the last set of Dietary Guidelines for Americans (DGA), 2015-2020, all Americans were encouraged to eat fewer foods containing saturated fat. This isn’t the same as a prescription for a low-fat diet, which sometimes means replacing oils with carbohydrates, which could actually elevate LDL cholesterol (the “bad” cholesterol) and distract people from eating and enjoying healthy fats.
What’s the moral of this story? Unless a physician or registered dietitian/nutritionist has prescribed a low fat diet for a specific purpose, eat and enjoy unsaturated oils guilt-free and try to aim for a dietary pattern focused on quality and appropriate portions.
What is a “nutritious oil”?
Cooking oils are usually liquid at room temperature and are made of a mix of unsaturated fatty acids called monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA). They come from plant or fish sources. The exceptions to this are coconut oil, palm oil and palm kernel oil, which are mostly made of saturated fatty acids.
Animal and dairy fat are also mostly saturated fats because they’re solid at room temperature. Saturated fat has been linked to elevated LDL cholesterol levels and increased risk of heart disease.
The American Heart Association recommends lowering the amount of saturated fat in your diet by replacing it with better-for-you unsaturated fats, the MUFAs and PUFAs.
A brief chemistry class
Fat is made up of triglycerides, or a glycerol molecule with three fatty acids attached. Fatty acids can be divided into two categories: unsaturated fatty acids and saturated fatty acids. Saturation refers to how the fatty acid’s carbon molecules connect with each other. Saturated fats have no double bonds -- only single -- meaning all carbons are matched with other carbons. They are orderly and fall in line with each other making a nice, neat solid fat at room temperature.
Unsaturated fats, on the other hand, like MUFAs and PUFAs, contain one or more double bonds, which makes them bendy and liquid-y at room temperature. PUFAs are home to a special subset of fatty acids — omega-3s and 6s — important for a variety of human functions. Omega-3 oils are also being researched in connection with infant health, cancer prevention, Alzheimer’s disease, cognitive function and rheumatoid arthritis. Omega-6 oils provide energy and contribute to cell structure.
There are two PUFAs the body needs but can’t make -- called essential fatty acids, omega-6 linoleic acid (LA) and omega-3 alpha-linolenic acid (ALA). ALA can be converted to EPA and DHA (also omega-3s), which are usually only available in fish and other marine sources. If it’s not possible for a person to include fish in their diet, then ALA-containing oils become very important in order to make EPA and DHA. Higher ALA oils include flaxseed, canola and soybean oil. ALA is primarily thought to be beneficial in reducing the risk of heart disease by maintaining normal heart rhythm and pumping.
Each oil contains all three types of fat — saturated, poly- and mono — in differing proportions and this is what gives each oil its unique characteristics. Generally speaking, unsaturated fats lower bad cholesterol and triglyceride levels, reduce the risk of cardiovascular disease, and are linked to an over-all lower cause of death. Promising new areas of research for fats include diabetes and metabolic syndrome.
Which oil is best for me?
Penny Kris-Etherton, Ph.D., registered dietitian and distinguished professor of nutrition at Penn State University, has this advice: “Virtually all liquid vegetable oils are preferred over solid fats. So, canola oil, soybean oil, corn oil and olive oil (among others like sunflower, safflower, cottonseed and nut/peanut/seed oils) are recommended. The oils that are higher in PUFA — like corn oil vs. olive oil — will lower LDL cholesterol more and olive oil (extra virgin) is known for its bioactives that have health benefits. Beyond choosing a liquid vegetable oil for taste, there are other benefits (LDL-C lowering) that could guide purchasing decisions.”
Partially hydrogenated oils containing trans fatty acids (TFA) had been used in the commercial food industry in response to the low-fat diet craze. They help maintain a product’s shelf life and were viewed as healthy replacements for saturated fat. Research now shows that man-made TFA are detrimental to human health. Replacements for trans fats include high oleic oils, fully hydrogenated oils (high in stearic acid) and tropical oils (mainly palm oil). The impact these oils have on health has not been substantiated either pro or con and requires more research.
There are many studies that compare the health benefits of different oils but it’s not practical for consumers to switch oils based on the results of each new study or trend. Key— choose unsaturated oils that fit your budget and culinary needs. Unsaturated, “better-for-you” oils include canola, corn, olive, peanut, safflower, soybean and sunflower. If a product is sold as a “vegetable” oil it will contain these oils or a blend of them. Higher-end, specialty vegetable oils that also contain appreciable amounts of poly- and mono-unsaturated fats include sesame, avocado, almond, flaxseed, hemp and walnut oil. Oils are usually excellent sources of vitamin E and have other naturally occurring antioxidants.
The best choice? Your favorite unsaturated oil as part of an overall food-based approach to health!