At a family get together, my brother-in-law requested that I write an article on fats—margarine, oil and butter. There had been a heated debate in his camp office last week revolving around oil. One of his colleagues insisted that vegetable oil is as healthy as canola oil, and another said that she uses olive oil for everything. He asked that I write an article to help explain the difference between the various fats and how they should be used. So, Yigal, this one is for you.
Fat is an essential nutrient used by the body to dissolve certain vitamins and provide insulation and energy. Also, fats make up the main structural component of cell membranes. However, not all fats are equal. All fats contain fatty acids which are made up of a chain of carbons, oxygen and hydrogen atoms. The term saturated fat refers to carbon atoms which have as many hydrogen atoms as possible attached to them. Monounsaturated fat (MUFAS) refers to a fatty acid chain where in one place the carbons are not saturated with hydrogen and in polyunsaturated fats (PUFAS) the fatty acid chain has two or more places where the carbons are unsaturated.
All foods containing fat have a combination of saturated fats, MUFAS and PUFAS. The proportion of how much of the fat is saturated as to how much is MUFAS and how much is PUFAS makes a crucial difference both on food and on health. Fats in which the majority of the fatty acids are saturated are usually solid at room temperature. These fats, such as butter and shortening, tend to be more stable. The fat in dairy and meat as well as some tropical vegetable oils such as coconut, palm and palm kernel oil are also high in saturated fats. Oils such as sunflower, corn, safflower and soybean are high in PUFAS and tend to be liquid at room temperature. These fats are not as shelf stable as saturated fats. Canola and olive oil are oils high in MUFAS and are therefore not as shelf stable as saturated fats.
With an understanding of the properties of the various fatty acids it is now easier to understand trans-fats and how man-made trans-fats came to be. Trans-fat refers to a fatty acid which has hydrogen atoms added. The result is that vegetable oils can become more solid (margarine) and more shelf stable, which is ideal for snack foods and bakery items. The process of hydrogenating oil and turning it into margarine was originally done in a quest to find an alternative to butter. More recently, however, trans-fats have been under major scrutiny, because they raise cholesterol and higher intake is associated with higher risk of developing coronary heart disease, cancer, Alzheimer’s disease and diabetes. Interestingly, beef, butter and milk contain small amounts of naturally occurring trans-fat which do not seem to raise cholesterol levels or have the same adverse effects as man-made trans-fat.
Diets high in saturated fat, found in abundance in animal products, coconut oil, chocolate and other processed foods are also thought to be a risk factor for cardiovascular disease as well as certain cancers. Yet, diets high in monounsaturated fats can help reduce LDL cholesterol and may raise HDL cholesterol. (HDL cholesterol is known as the “good cholesterol” as it transports cholesterol back to the liver, and higher levels of HDL cholesterol may reduce risk for heart disease.) Olive oil, avocadoes and canola oil are all good sources of monounsaturated fat. Finally, polyunsaturated fats, found in nuts, seed, fish and many oils, can help reduce LDL cholesterol, but may also decrease HDL cholesterol. Omega three fatty acids, a type of PUFAS which are essential to our body, have been linked to a multitude of health benefits including reducing inflammation, the risk for heart disease and may help in the management of diabetes, arthritis and depression. While omega six fatty acids are also essential to our bodies, they compete with omega three for the same metabolic pathway making it imperative that our diet has the proper ratio between these two fatty acids. Because the current western diet is heavy on soybean and other vegetable oils rich in omega six, the crucial omega three fatty acids are not as easily utilized by our bodies. For this reason it is recommended to use more canola, flax seed and walnut oil and less vegetable oil.
By Shoshana Genack MS, RD