When Vegetable Oil Isn’t as Healthy as You Think

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What Happens When We Cook With Vegetable Oils, Are They Good For Our Health?

The consumption of vegetable oils has increased dramatically in the past century. We were all trained that vegetable oils were good and butter was bad. Most mainstream health professionals consider them healthy, but vegetable oils may cause health problems. Their health effects vary depending on what fatty acids they contain, what plants they are extracted from, and how they are processed.
Despite their potential health benefits, some scientists are worried about how much of these oils people are consuming. These concerns mostly apply to oils that contain a lot of omega-6 fats.

All fats contain a blend of saturated (SFA), monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids, and vegetable oils are no exception. Each type of seed has its own signature blend of the dozens of possible fatty acids that occur in nature, and each fatty acid is either a saturated, monounsaturated or polyunsaturated fatty acid.

Fat is more resistant to heat if it contains fewer double bonds between its molecules. Double bonds oxidize and break down easier when exposed to heat.

Saturated fats (SFA): These do not contain any double bonds and are solid at room temperature.

Monounsaturated fats (MUFA): is a type of dietary fat. It is one of the healthy fats, along with polyunsaturated fat. Monounsaturated fats are liquid at room temperature, but start to harden when chilled. These contain only one double bond but are also stable at high temperatures.

Polyunsaturated fats (PUFA): are made up of omega-6 and omega-3 fatty acids. These have two or more double bonds, which make them prone to oxidation.

Omega-3 fatty acids are found in foods from plants like soybean oil, canola oil, walnuts, and flaxseed. They are also found in fatty fish and shellfish as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Salmon, anchovies, herring, sardines, Pacific oysters, trout, Atlantic mackerel, and Pacific mackerel are high in EPA and DHA and lower in mercury.

Omega-6 fatty acids are found mostly in liquid vegetable oils like soybean oil, corn oil, and safflower oil.

Most vegetable oils require significant industrial processing. Heat, cold, high-speed spinning, solvents like hexane, degumming agents, deodorizers, and bleaching agents are typically used to process the seeds into a palatable oil. The unsaturated fats found in vegetable oils, when they’re heated, tend to oxidize. In this form, they’re more dangerous to body tissues and can trigger inflammation. Inflammatory conditions have gotten worse and worse because seed oils are not natural. You need chemicals, heat in a factory to get the oil out of these seeds.

Which oil is right for you? That depends largely on the type of cooking you’re doing. An oil’s smoke point, which is the point when oil starts burning and smoking, is one of the most important things to consider. If you heat an oil past its smoke point, it not only harms the flavor, but many of the nutrients in the oil degrade—and the oil will release harmful compounds called free radicals.

Olive oil

Nutrition and cooking experts agree that one of the most versatile and healthy oils to cook with and eat is olive oil, as long as it’s good quality extra virgin. “You want an oil that is not refined and overly processed. An “extra virgin†label means that the olive oil is not refined, and therefore of high quality. Extra virgin olive oil contains a large amount of monounsaturated fats and some polyunsaturated fatty acids; many studies have linked it to better heart health. Olive oil has a relatively lower smoke point compared to other oils, so it’s best for low and medium-heat cooking.

Coconut oil

For starters, coconut oil, especially virgin coconut oil, is rich and flavorful. Before you begin cooking with coconut oil, it’s important to understand which type you’re using. The smoke point of virgin coconut oil is 350°F — best for baking and sautéing. The smoke point of refined coconut oil is 400°F, which makes it a better option for frying or cooking at higher temperatures. In most cases, you can substitute coconut oil 1:1 for other oils and butters. One of the biggest reasons coconut oil is all the rage. It’s also a great animal-friendly alternative to butter. Coconut oil is primarily saturated fat. Nutrition-wise, coconut oil, especially virgin coconut oil, is said to have antioxidants and anti-inflammatory properties. Refined coconut oil and partially hydrogenated coconut oil can actually be harmful, as they may contain chemicals, bleach, or trans fats. Reach for virgin or unrefined coconut oil (organic whenever possible) for optimal health benefits.

Saturated fats can be a healthier oil to use when you’re cooking at a very high temperature or frying food (something that definitely should be done in moderation) because they are more stable at high heat. This means that they are less likely to break down and smoke.

Avocado oil

Avocado oil is a great choice. It’s unrefined like extra virgin olive oil, but it has a higher smoking point, which means it can be used to cook at higher heat and is great for stir-frys. It doesn’t have much flavor, which makes it a good option for cooking. Avocado oil contains both monounsaturated and polyunsaturated fatty acids (it has one of the highest monounsaturated fat contents among cooking oils) as well as vitamin E. One downside is that it tends to be more expensive.

Sunflower oil

This oil is high in vitamin E; one tablespoon contains 28% of a person’s daily recommended intake of the nutrient. It has a high smoke point and doesn’t have a strong flavor, which means it won’t overwhelm a dish. However, sunflower oil contains a lot of omega-6 fatty acids. The body needs them, but omega-6s are thought to be pro-inflammatory, while omega-3s are anti-inflammatory. Consuming too many omega-6s without balancing with omega 3s, could lead to excess inflammation in the body, so moderation is key.

Peanut oil

Peanut oil has one of the highest monounsaturated fat contents among cooking oils. The omega-6 fatty acids in peanut oil can be harmful if your diet consists of too much of this type of fat. Many Americans already consume a diet high in omega-6 fats, which are found in vegetable oils, fast food, and many packaged products.

Walnut oil

This oil has a low smoke point, so it’s not good for cooking, but it can be used in plenty of other ways. Walnut oil has a good ratio of omega-6 to omega-3 fatty acids, which helps keep inflammation in check.

Flaxseed oil

Flaxseed oil is high in omega 3s and has a very low smoke point, which means it also shouldn’t be used for cooking. I use flaxseed oil for dressing. Make sure it’s stored at a low-temperature location, like in the refrigerator.

Sesame oil

This oil is often used for its potent flavor; a little goes a long way. It contains both monounsaturated and polyunsaturated fatty acids, though it’s not especially high in other nutrients. Light sesame oil has a higher smoke point and can be used for high-heat recipes, while dark sesame oil (from roasted sesame seeds) has a slightly lower smoke point and is unsuitable for high heat.

Vegetable oil

The term “vegetable oil†is used to refer to any oil that comes from plant sources, and the healthfulness of a vegetable oil depends on its source and what it’s used for. Most vegetable oils on the market are a blend of canola, corn, soybean, safflower, palm, and sunflower oils. “Generally I tell people to use olive oil or avocado oil whenever they can instead of corn or soybean oil.

Vegetable oils are refined and processed, which means they not only lack flavor but also nutrients. Vegetable oil is guaranteed to be highly processed. It’s called ‘vegetable’ so that the manufacturers can substitute whatever commodity oil they want—soy, corn, cottonseed, canola—without having to print a new label. Processed oils have been pushed past their heat tolerance and may become rancid in the processing.

Canola oil

Canola oil is derived from rapeseed, a flowering plant, and contains a good amount of monounsaturated fats and a decent amount of polyunsaturated fats. Of all vegetable oils, canola oil tends to have the least amount of saturated fats. It has a high smoke point, which means it can be helpful for high-heat cooking. That being said, in the United States, canola oil tends to be highly processed, which means fewer nutrients overall. “Cold-pressed†or unprocessed canola oil is available, but it can be difficult to find.

If you eat out, chances are your food is cooked in some type of vegetable oil. If you buy packaged goods like crackers, chips, or cookies, there’s a very good chance that vegetable oils are in the ingredients list (soybean, corn, canola, cottonseed, safflower, sunflower). If you buy spreads, dips, dressings, margarine, shortening, or mayo, the likely star ingredient is vegetable oils.

Most vegetable oils contain predominately omega-6 fatty acids and contribute to the abundance of omega-6 fatty acids (over omega-3 fatty acids) in the standard American diet. Scientists have hypothesized that eating too much omega-6 can lead to increased inflammation in the body and potentially contribute to disease.

Commercial vegetable oils may also contain trans fats, which form when the oils are hydrogenated. Food producers use hydrogenation to harden vegetable oils, making them solid like butter at room temperature.

For this reason, vegetable oils found in margarine are commonly hydrogenated and full of trans fats. A high intake of trans fats is associated with all sorts of chronic diseases, including heart disease, obesity, cancer, and diabetes.

If a product lists hydrogenated oil as an ingredient, it likely contains trans fats. For optimal health, avoid these products.


Both omega-6 and omega-3 fatty acids are essential fatty acids, meaning that you need some of them in your diet because your body can’t produce them.

Scientists have hypothesized that too much omega-6 relative to omega-3 may contribute to chronic inflammation. Chronic inflammation is an underlying factor in some of the most common Western diseases, such as heart disease, cancer, diabetes, arthritis, obesity, asthma, psychiatric disorders, and autoimmune disease.

At this point, there’s still quite a bit we don’t know about vegetable oils. Consuming small amounts of vegetable oils might make sense for some of us, depending on lifestyle, food preferences, and other factors. However, if your goals include eating less processed foods, as I prefer to do, the best course may be to avoid these inflammatory oils and return to traditional dietary fat sources. Get your fats from whole foods, including avocados, oily fish, nuts, seeds, olive oil, traditional oils, butter, coconut oil, and meats. Consider baking and broiling your foods instead of frying them.

Factory foods can be very unhealthy and very inflammatory. Every cell in your body is made of fat cholesterol. When your feeding your cells hydrogenated unsaturated fats, your cell membranes are being made of these fats. This will increase oxidative damage, autoimmune conditions, and aging.