Learning the best ways to use oils is an essential part of making healthy food at home. From healthy frying to baked goods, choosing the best oil for a given dish is essential to preparing healthy, flavorful food. As much as its been bashed in the media, cooking oil is essential for tasty, healthy foods. It helps retain moisture and adds flaky, tender texture. It also provides fat,which is an essential part of healthy eating. Choosing the most best vegetable oil for a given dish requires weighing the health benefits of the oil against what it contributes to the recipe. Cooking temperature, flavor, and contribution to texture all come into play.
Oils are derived from either plant or animal sources, with the term broadly used to describe blends of chemical substances, broadly referred to as fats. Fats and oils share a common chemical structure, and are differentiated primarily by their melting point. Fats are solids at room temperature, while oils are typically liquids.
Both can be broken up into two classes; saturated or unsaturated. Unsaturated fats can be further divided into mono- and poly-unsaturated types. Chemically speaking, these compounds are the result of combining fatty acids with glycerol. Primary differences between them are the chain length of the fatty acid portion (i.e. the number of carbons), and their geometric arrangement in 3-dimensional space. When it comes to cooking healthy, the chef’s choices are limited based on thermal stability; that is, how long it will be exposed to high temperatures, and what temperatures they will see. Polyunsaturated types are usually the least stable to high heat, by virtue of having the greatest number of double bonds, followed by monounsaturated, and then saturated. Since most cooking oils are derived from naturally occurring sources, each has its own unique contribution to health, texture, and flavor in the kitchen.
Saturated Oils
Chemically speaking, oils high in saturated fats have no double bonds along the fatty acid chain. Most prevalent among animal sources, saturated oils generally have higher melt points than unsaturated types, which means they are more likely to be solids or semi-solids at room temperature. Generally speaking, when we hear news about the dangers of a high fat diet, the focus is on saturated oil and cholesterol. These are most prevalent in animal-based sources, like lard and suet.
The lack of unsaturation (double bonds) along the fatty acid chain raises the melting point of saturated oils, improves their stability to high temperature cooking by raising the smoke point and increases long term storage stability. Partially hydrogenated cooking oils are those in which some, but not all, of the double bonds have been synthetically removed. This increases the degree of saturation, making the oil behave more like a saturated type. The process of hydrogenating lengthens the time it will take for an oil will go rancid. Hydrogenating also creates trans fats which have been shown to raise cholesterol.
Recipes that call for saturated fats usually take advantage of the melting point or thermal stability. Baked goods that are flaky often contain saturated fats that are “cut” in with a fork, rather than being blended. By dispersing small chunks of it throughout the flour, as the bread rises, the fat melts, leaving a small globule of rich, fatty goodness that is responsible for the flaky texture.
While the most common sources of saturated fats include animal-based fats and partially hydrogenated oils, there are some vegetable-based cooking oils that contain higher concentrations of saturated fats. The most common are palm, coconut, and palm kernel oil. These saturated vegetable oils are often used to replace partially hydrogenated types in food products. This allows producers to label the product as being free of trans fats, or free of partially hydrogenated oils. One example is the use of palm oil in separation-free “All Natural” peanut butters. The palm oil, which is a solid at room temperature, thickens the mixture. This prevents liquid oils from rising to the top of the jar during storage.
Unsaturated Oils
Unsaturated types are, by contrast, those which have one (mono) or more (poly) double bonds along the fatty acid chain. These oils are generally liquids at room temperature, and are more often obtained from plant-based sources. Often referred to as omega-3 or omega-6 acids, polyunsaturated oils can be told apart by the location of the double bond within the molecule. Precursors to many important substances in the body, many polyunsaturated oils are considered essential oils, because they are necessary for proper growth, and can only be obtained through a healthy diet. These can not be synthesized by the body. Monounsaturated types usually behave similarly to saturated fats, in that they promote insulin resistance and have been positively correlated with breast cancer. However, monounsaturated oils have shown the potential to reduce both LDL levels and cholesterol. Monounsaturated fats offer the advantage of being suitable for high temperature cooking, with some level of health benefits.
Most of the research into the health benefits of polyunsaturated types suggest that consuming an excessive amount of omega-6 to omega-3 oils is linked to negative health effects, including breast cancer, prostate cancer, heart attack, and stroke. Unfortunately, traditional Western diets seem to be weighted heavily toward omega-6 types, to the tune of as much as 10:1. This skewing is easily explained by the move from saturated fats to vegetable-based oils for frying and cooking. Seed and vegetable oils such as those from canola, corn, cottonseed, sunflower, and safflower all tend to be biased toward omega-6 fatty acids.
Omega-3 types are thought to be among the most healthy of the unsaturated types. Research has associated omega-3′s with reduced heart rate, reduced risk of atherosclerosis, lower triglycerides, and lower overall blood pressure. There are indications that cooking with omega-3 fats may improve brain and eye function, and several studies are examining the potential for omega-3′s to reduce a host of psychological disorders. Despite all their health benefits, there are downsides. A diet rich in omega-3′s may increase the effectiveness of blood thinners, raise blood sugar levels, and interfere with blood sugar lowering medications, which makes them a less than ideal when cooking for diabetics.
Unfortunately, the best sources of omega-3 types are cold-water fishes such as tuna, flounder, grouper, cod, and salmon. Few vegetable-based sources are rich in omega-3′s, which makes them hard to produce using industrial methods. Couple this with the fact that most polyunsaturated oils decompose rapidly at high temperatures, and the problems become apparent.
The most commonly cited plant source of omega-3′s is flax seed oil, but even at that lacks the most healthy form of omega-3. Other vegetable sources include canola, walnuts, grape seed, pecans, and hazel nuts. Fats accrued from grass-fed animals tend to be richer in omega-3 fatty acids than their grain-fed counterparts as well. Polyunsaturated types are quite fragile, and oxidize rapidly at high temperatures, which destroys the health benefits. These types even decompose at room temperature in the presence of oxygen. Most experts suggest storing them sealed, in the refrigerator, to preserve their benefits.
The following table displays some of the most relevant information for looking for a healthy oil. Of importance are the ratio of saturated fat to omega-6 and omega-3, the smoke point and the combustion temperature. Cooking methods that make use of higher temperatures and longer times require higher smoke points to avoid decomposition.
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As you can see, when you’re looking at choosing a healthy oil, there is no straightforward answer. The “best” choice depends heavily on the demands of the recipe, and the heat profile it will see. Unfortunately, those that are the most healthy are, usually speaking, less thermally stable. But, with some changes in diet and behavior, we can seek to insert some of the healthier omega-3 fats in place of other, less healthy oils.
Written by Greg. Updated December 2011.
References
- “Saturated Fats” American Heart Association. Accessed November 2011.
- “Saturated Fats” Center for Disease Control. Accessed November 2011.
- “Polyunsaturated Fats and Monounsaturated Fats” Center for Disease Control. Accessed November 2011.
- “Dietary Fats. Knowing Which Fats To Choose” MayoClinic.com. Accessed November 2011.
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