Things to Consider When Choosing a Fat or Oil

Type of Fat

When choosing fats and oils for use in the kitchen, it is critical to take into consideration the fatty acid composition, which refers to the percentage of polyunsaturated (which includes the omega-3 and omega-6 fats), monounsaturated and saturated fats found in the oil. Even though we tend to classify fats as one or the other (olive oil is monounsaturated, coconut oil is saturated, etc.), all fats are a combination of all three types of fatty acids, with the predominant type giving rise to its common classification. While all three types of fats are important for health, they are not all equally stable when exposed to heat during cooking. To say a fat is stable means it is more resistant to oxidation caused by heat, light, and oxygen. Oxidation is a process of breaking down and when this happens to an oil outside the body, before it has been ingested, the oil is said to be rancid. Consuming rancid oils increases free radical damage throughout the body.¹ Saturated fats are the most stable, while polyunsaturated are the least stable, and monounsaturated fall somewhere in between. So from the perspective of using oils appropriate for cooking, the general rule is, oils that are predominantly saturated are the most suited to cooking, oils that are predominantly monounsaturated are stable at low to medium heat*, but oils that are predominantly polyunsaturated should not be exposed to heat at all.

*Low heat is defined as 255-300°F and medium heat is defined as 325-375°F; 400°F and above would be high heat (http://www.onlineconversion.com/cooking_gasmark.htm)

Type of Processing

An oil’s journey to the grocery shelf is equally important to consider since some methods of processing can damage delicate fatty acids, resulting in an oil that is rancid. The first step for processing oil is to get the oil out of the raw material (nut, seed, fruit, grain or legume). Traditionally, humans consumed fats from animals, such as butter and lard, and oils like olive, coconut, fish, flax and palm that were easily extracted using slow-moving stone presses or rollers, which preserved the integrity of the fatty acids. Today, manufacturers who use mechanical means to extract their oils are using a modern version of the ancient oil press. If the mechanical extraction is done without the use of heat it is called cold-pressed (a.k.a. cold extracted); if heat is employed it is called pressed or expeller pressed. Chemical solvents (e.g., hexane) are also used as an extraction method. After extraction, the solvent is removed, and most companies claim that only trace amounts, if any, of the solvent remains in the oil. Once the oil has been extracted using one of these methods, it can be sold as is and labeled as unrefined. Unrefined oils tend to retain the color, flavor and nutritional characteristics of the raw material they were extracted from. The oil can also go on to be refined through further processing. In the refining process the oil is exposed to conditions that can damage the unstable fatty acids and render the oil rancid. After refining, the oil must first undergo bleaching and deodorizing (and sometimes degumming and winterizing) before it is considered fit for human consumption.² This process removes impurities—those  created by the refining process, but also valuable “impurities” such as antioxidants, chlorophyll, phytosterols, and lecithin.³ The refining process (in particular, deodorizing) also damages some of the delicate fatty acids, creating small amounts of trans fats.⁴ Refined oils tend to have a neutral taste and be light in color (e.g., vegetable and corn oil). Solvent- or chemical-extracted refined oils have become common because they are cheap to produce and, once the oil has undergone such extensive processing, it is more shelf stable, two traits which work in favor of manufacturers wanting to increase their profits. Chemical extraction and refining methods also increase yields of oils from raw materials that don’t yield much by more traditional methods. Refined oils not only contain damaged fats that are detrimental to our health, but they are also stripped of valuable nutrients, making them a poor choice for cooking.

Antioxidant Content

A high level of naturally occurring antioxidants found in some oils can help to prevent the formation of free radicals as oil sits on the shelf and while being used in cooking. Some oils, such as high quality, unrefined, extra virgin olive oil, are naturally high in antioxidants. These natural antioxidants help to make the oil more stable and thus more suitable for cooking.

Smoke Point

The smoke point of oil refers to the temperature at which an oil starts to visibly smoke. As oil reaches the smoking point, it produces toxic fumes and harmful free radicals. Smoke point is often used to determine which oils are best for which application and as a guide to know when an oil has been heated too high.  While this is somewhat helpful, from a nutritional standpoint, smoke point alone is not enough to determine which oils are best for cooking, especially because damage to the oil can start occurring before it reaches its smoke point.

Organic

If an oil bears the USDA organic certification symbol, the original raw ingredient (olives, coconut, sesame seeds, etc.) was grown in accordance with organic standards and is free of synthetic pesticides. Organic standards required to earn the USDA organic seal also prohibit the use of volatile synthetic solvents, such as hexane.⁵ For more information about the Organic Standards, please see the Customer Literature File Organics.

In general, for the healthiest and tastiest fats and oils, look for those that are cold or expeller pressed, unrefined, organic and come in a glass bottle, preferably a dark bottle that blocks out light, especially for oils that are high in mono- and polyunsaturated fats.

Below is a list of oils and fats with more specific information about each

Avocado Oil

Pressed from the avocado fruit, avocado oil has a fatty acid profile similar to olive with a high monounsaturated fat content. It too is high in antioxidants, making it appropriate for medium heat cooking. Avocado oil is also high in beta-sitosterols, which support healthy cholesterol levels and prostate health.⁶

Butter

This golden delicacy has been used for centuries. Butter is comprised mostly of saturated fat and is a valuable source of the fat-soluble vitamins A, D, E, and K. Butter from pasture-raised cows is also a good source of conjugated linoleic acid (CLA), a special fat that supports immune function and healthy weight management.⁷ Its lower melting point allows it to bestow wonderful texture to baked goods, but also makes it more likely to burn, so keep it for spreads, flavoring vegetable dishes, baking, and low to medium temperature sautéing.⁸ Look for dairy from animals that have been pasture-raised. Cows raised on pasture produce dairy that is more nutrient dense than dairy from conventionally raised cows. For more information, check out the Customer Literature Files Butter and for more information, check out this page.

Canola Oil

When it was first introduced to the US, canola was hailed as a “healthy” alternative cooking oil because of its higher percentage of monounsaturated fats. Today, there is much confusion surrounding canola oil and, while much of it is misinformation repeated over and over on the internet, canola is not without its problems. In its natural, unrefined form canola oil is comprised mostly of monounsaturated fats and a fairly high amount of polyunsaturated fats as well, making it appropriate for low to medium heat. While canola oil as it was first introduced was bred using traditional plant breeding techniques, a genetically engineered (or GMO) version of canola has been introduced and at present makes up about 90% of the US and Canadian canola crop.⁹ Another problem with canola is that it is commonly hydrogenated for use in the food industry. And the canola that escapes hydrogenation is often refined. If you choose to use canola oil be sure to look for organic or non-GMO varieties that are unrefined, and remember to use it at low to medium temperatures.

Clarified butter/Ghee

Ghee is butter that has had the milk solids (whey, casein, and lactose) removed.¹⁰ This is why those with an intolerance to milk often do well with ghee.¹¹ Ghee has a longer shelf life and is a very stable form of butter, which means it can be used in higher temperature cooking.^{12 13}

Coconut Oil

This was one of the oldest dietary fats used extensively in the 1800s.¹³ It contains unique saturated fats know as medium chain fatty acids (MCFAs) that are digested and handled by the body differently than other fats. MCFAs speed up the body’s metabolism, support brain health, soothe the gut and are an excellent source of energy.¹⁴ The body also converts them into powerful antimicrobial agents capable of defending against bacteria and viruses.¹⁵ Coconut has good stability and is appropriate for baking, pan frying, sautéing, and making popcorn. While coconut oil is naturally solid at room temperature, liquid, ‘fractionated’ coconut oil is available. Fractionation separates the fatty acids based on melting characteristics. By removing some of the longer chain, slow melting fatty acids, the resulting oil is liquid and contains a higher concentration of medium chain fatty acids. Learn more information on the health benefits of coconut.

Grape Seed Oil

Pressed from the seeds of grapes, this oil is a by-product of wine making. The oil can be difficult to extract so care should be taken to choose grape seed oil that has been cold- or expeller-pressed to avoid chemical solvents. Grape seed oil contains polyphenols and a high amount of vitamin E. It is sometimes promoted for frying and high heat cooking because it has a neutral taste and a high smoke point, however 85%-90% of its fatty acids are polyunsaturated, with the omega-6 fat linoleic acid being the most abundant, making it very susceptible to heat and not suitable for frying.^{16 17}

Lard

This is the fat rendered from the pig. It has been used extensively around the world for centuries (including in the United States, until the 1980s). Lard is mostly monounsaturated (48%), with a good amount of saturated fats and a lower polyunsaturated content, which makes it quite stable and a good choice for baking and frying. Because all animals store toxins in their fats cells, it is wise to buy grass-fed and/or organic lard. Also be aware that much of the lard sold in conventional grocery stores is hydrogenated and loaded with chemical preservatives and does not offer the same health benefits of real, clean lard.

Nut Oils

These flavorful choices have much to offer the palate. Several nuts oils, including macadamia, walnut, almond and hazelnut, possess high concentrations of powerful nutrients such as tocopherols, squalene, phytosterols and many other antioxidants, just like their whole nut versions.^18 13 Bear in mind that most nut oils are rich sources of polyunsaturated fatty acids, which are the least stable types of fat and are easily damaged by heat, light and oxygen. In general, store these oils with the cap on, in the refrigerator and use them on salads and as finishing oils to jazz up an already cooked dish with their stronger, distinct flavors.

• Almond Oil is being noticed for its ability to lower triglyceride levels while increasing HDL (good) cholesterol.¹⁹ While almond oil does have a high amount of stable monounsaturated fats, it also has a fairly high amount of unstable polyunsaturated fats, which means it is probably best not used in heat applications.
• Hazelnut Oil is generally used as a gourmet oil. Although it is fairly high in monounsaturated fats, because of its strong flavor and higher cost it is usually used as a finishing oil. 
• Macadamia Nut Oil is high in monounsaturated fatty acids and low in polyunsaturated fatty acids, making this oil more stable and a good choice for low to medium heat cooking.
• Walnut Oil is rich in omega-3 fatty acids (beneficial, yet unstable polyunsaturated fats) and helps inhibit LDL cholesterol oxidation.²⁰ It should never be exposed to heat.

Olive Oil

Studies indicate that olive oil can inhibit LDL cholesterol oxidation and platelet aggregation, two factors involved in heart disease.^{21 22} Olive oil intake has also been associated with a lower risk of some cancers.²³ The protective actions of olive oil are partly due to its high antioxidant content.¹³ While olive oil is definitely good for you, it can be tricky to choose the best quality products since there are so many grades of olive oil, and recent tests have uncovered olive oils that do not meet the quality standards of the labeling grade they display.^{24 25} Extra-virgin is generally the highest quality olive oil available and is cold-pressed without the use of solvents; virgin olive oil is the next best. Refined olive oils or oils labeled as olive oil, olive-pomace oil or “light” are the lowest quality and have generally undergone the highest amount of processing and may even be mixed with other cheaper refined oils. In the US there are no legal requirements for the use of these labeling grades. Manufacturers can voluntarily participate in a USDA Quality Monitoring Program, which evaluates oils based on U.S. grade standards, but there is no requirement. To ensure you are getting the oil promised on the label, look for those that are certified by the USDA Quality Monitoring Program (QMP) or the International Olive Council or those produced in the state of California, since the California Department of Food and Agriculture has set up strict standards for labeling.^{26 27 28} Because of olive oil’s high monounsaturated fatty acid content and its high level of antioxidants, it can be used for low to medium heat cooking as well as for salad dressings and as a finishing oil.

Palm Oil

This tropical oil is extracted from the fruit of the palm, which is up to 70% oil. Because of its high oil content, solvent extraction is unnecessary, resulting in a cleaner end-product.¹³ Palm oil has high levels of carotenoids, along with the vitamin E family of nutrients called tocopherols and tocotrienols. This oil is mostly saturated, making it a good choice for higher heat applications, such as frying.¹³ This oil is also commonly found in natural shelf-stable shortenings.

Peanut Oil

This oil is fairly stable because it is mostly monounsaturated fats and it has a high antioxidant content. It does have a fairly high amount of polyunsaturated fats too, though, so it is probably best used for cooking at no higher than medium heat.

Seed Oils

These oils pressed from a variety of edible seeds tend to be rich in omega-3 and omega-6 polyunsaturated fatty acids, which means, while they may be good for you, they should be kept refrigerated with the lid on and they should not be heated. Instead, these oils are appropriate for making salad dressing or drizzling on cooked foods as finishing oils.  

• Flaxseed Oil that has not been refined has a golden yellow color and a slightly grassy smell. Because omega-3 polyunsaturated fats comprise up to 60% of the oil, it should not be heated and should be kept refrigerated.¹³
• Hemp Seed Oil is extremely high in polyunsaturated fats, with the majority of them being omega-6 fats. It has a green color owing to its high concentration of chlorophyll. Hemp oil should be kept refrigerated and should not be heated.
• Pumpkin Seed Oil is dark green and smells and tastes slightly nutty. It is high in antioxidants, such as vitamin E, and may support cardiovascular, urinary and prostate health.^{29 30} It is predominantly comprised of omega-6 polyunsaturated fatty acids.
• Sesame Seed Oil, unlike most other seed oils, is appropriate for up to medium temperature cooking. Even though it contains nearly equal amounts of mono and polyunsaturated fats, it also contains unique antioxidants which help to protect it when exposed to heat. Sesame oil can be added to other (non-polyunsaturated) oils to enhance their stability during heating.¹³
• Sunflower Oil is high in omega-6 polyunsaturated fatty acids and should not be heated, but unfortunately it is often exposed to heat in commercial food manufacturing practices. High oleic sunflower oil has been bred to have a very high percentage of monounsaturated fats, with much lower amounts of polyunsaturated fats, which makes it appropriate for low to medium heat applications. 
• Safflower Oil is high in omega-6 polyunsaturated fatty acids and should not be heated either. Unfortunately, it too is often used in commercial food manufacturing processes that expose it to heat. Like sunflower oil, there is also a high oleic safflower that has been bred to have higher amounts of monounsaturated fats and lower polyunsaturated fats, which makes it an acceptable option for low to medium heat applications.

Tallow

This fat is rendered from ruminants such as cattle, sheep or lamb and has a long history of human use. Because it contains 50-55% saturated fat, 40% monounsaturated and just a small amount of polyunsaturated fat, it is very stable and not likely to become rancid with normal use. It can be used for sautéing and frying. Because all animals store toxins in their fats cells, it is wise to buy grass-fed and/or organic tallow.

Vegetable Oils

This is the general term used to refer to a variety of oils that may include corn, soy, safflower, sunflower, and cottonseed oil. These oils are all high in omega-6 polyunsaturated fatty acids, which means they are very unstable and should not be exposed to heat. Yet, these oils form the basis of modern food manufacturing, where they are usually highly refined and then used in everything from baked goods and chips to soups and margarines. The abundance of these inferior oils in our food supply is often blamed for the inflammation epidemic we are currently experiencing, since an overabundance of omega-6 fats, which tend to be inflammatory, upsets the balance with the omega-3 fats, which tend to modulate inflammation. Furthermore, in the US as of 2015, 92% of the corn, 94% of the soy and 92% of the cottonseed that these oils come from are genetically modified (GMO).³¹ These oils, often sold as a “vegetable oil blend”, should be avoided both in processed foods and in your home. For more information on how fats influence inflammation or genetically modified foods, please see the Customer Literature Files Fats—Inflammation Modulation and GMOs.

Using and Storing Oils

In summary, oils most suitable for cooking and sautéing include coconut, palm, sesame, peanut, olive, avocado, and macadamia nut oils as well as butter and ghee. For an all-purpose light frying oil, combine coconut, sesame and olive oil in equal proportions. For those few dishes that require cooking at higher temperatures, look to palm or coconut oil, grass-fed lard or tallow. Baking usually turns out best with solid fats such as butter, coconut oil, palm oil and grass-fed lard. Those oils that should always be left unheated include flaxseed oil, most nut and seed oils and any other highly polyunsaturated oils.

Once you have chosen the best oils for your cooking needs, be sure to store the oils properly to protect them from heat, light and oxygen, the three drivers of oil rancidity. Be sure to keep all oils tightly capped when not in use to minimize oxygen exposure. Store oils in a dark place to protect from light. And be sure to store all polyunsaturated rich oils in the refrigerator; monounsaturated oils can also be stored in the fridge, especially if you won’t be using them very fast. Saturated fats are usually stable enough to store in a cool dark place but can be refrigerated or frozen if you won’t use them quickly.

References

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