Is Vegetable Oil Healthy Or Bad For You?
vegetable oil

The Ugly Truth About Vegetable Oils

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Our consumption of vegetable oils has rapidly increased in the past century. In fact, refined vegetable oils became available in the beginning of the 20th century, which is when the technology used to produce them was developed.

They are generally very cheap, usually have a high smoking point, and are widely available in the whole world. Almost every household in the world will have a bottle of vegetable oil.

Additionally, hydrogenated vegetable oils, an important source of harmful trans fats, are extensively used in the production of processed foods.

What are their effects on health, though? Should we be concerned about the increasing consumption of vegetable oils? What are the types of fats contained in vegetable oils?

Let’s find out.

What Are Vegetable Oils?

“Vegetable oils” is a general term used to describe highly refined oils produced from some plants and seeds.


They are highly processed and purified, and the extraction of fat from these plants is complex and in most cases utilises very high temperatures, solvents, and other harsh chemicals.

In other words, vegetable oils are highly unnatural (unlike more oils that were used for many centuries, such as olive oil or coconut oil, where applying mechanical pressure is sufficient to extract the oil from the plant).

There are many different types of vegetable oils, and some of the most popular are:

Soybean Oil

Soybean oil is one of the most widely used vegetable oils, used in many types of processed foods. It’s high in Omega 6s and is often partially hydrogenated.

Canola Oil

Canola oil is produced from the plant rapeseed through a very complex extraction process, after which the oil is refined and partially hydrogenated. Rapeseed contains erucic acid, which is toxic. Not to mention, more than 90% of canola crops are GMO (genetically modified) for herbicide resistance (1).

For that reason, canola oil was mostly used as an industrial oil before producers found a way to make an edible oil with low erucic acid content. Still, why would anyone consume a product that needs a series of complex chemical processes just to make it less toxic?

Safflower Oil

An oil that requires a complex industrial process to be extracted and refined.

Some types of safflower oil are high in monounsaturated fats, which are generally much better than polyunsaturated Omega-6s, and can even be cold-pressed. Still, it’s far from ideal.

Cottonseed Oil

An oil that needs to undergo heavy refining to remove gossypol, a toxin. Unrefined cottonseed oil can be used as a pesticide in some cases.

Corn Oil

The Omega-6 to Omega-3 ratio in corn oil is around 46:1 which is definitely something you want to avoid (2).

Grape Seed Oil

An oil that is pressed from grape seeds and oxidises easily when used for high heat cooking (such as deep frying).

Sunflower Seed Oil

Different varieties of seeds can be used for its production, which means that its monounsaturated and polyunsaturated fat profile varies.

Some sunflower oil will be hydrogenated or partially hydrogenated, i.e. containing trans fats.

Peanut Oil

Similarly to other vegetable oils, it’s prone to oxidation from exposure to light, heat or air.

It is somewhat better than some other vegetable oils as it contains a relatively high amount of monounsaturated fatty acids. However, it’s still high in Omega-6s.

What Are The Properties Of Vegetable Oils That Make Them Unhealthy?

#1. High Omega-6s To Omega-3s Ratios In Vegetable Oils

Both Omega-6s and Omega-3s are polyunsaturated fatty acids. Polyunsaturated fatty acids make up a big part of most vegetable oils.

Fatty acids are not only used for energy or stored as body fat, they are also one of the compounds of cell membranes (3).

Now, in and by themselves both Omega-6 and Omega-3s are essential to human health, as our bodies cannot produce them, which means that we need to get them from food.

In fact, most of the fat in the human body is either saturated or monounsaturated (those two make up about 97% of the total fat of the human body), while only 3% is polyunsaturated fat. Of it, half is Omega-3, half is Omega-6 fatty acids.

The 1:1 balance is important for optimal health, and that’s also the ratio our ancestors were consuming in some parts of the world (4).

A ratio of up to 4:1 might still be perfectly okay (this is what is often quoted by healthcare professionals), but with the rapid increase in the consumption of vegetable oils in the past century, most people nowadays are consuming fats in ratios that are way out of proportion, up to 20:1 (5).

So, the problem with Omega-6 fatty acids (and the reason why they’re portrayed as “bad”) is that nowadays we’re eating way too much of them, compared to Omega-3s, and that this lack of balance can be very unhealthy.

The Omega-6 content in vegetable oils is usually extremely high, compared to Omega-3s and monounsaturated fats (6).

#2. Rancidity and Oxidation

Saturated fats are very stable as they contain no double bonds in their chemical structure. Monounsaturated fats (such as the fats contained in olive oil) have one double bond, and polyunsaturated fats contain two or more double bonds.

For that reason, polyunsaturated fats (contained in vegetable oils) are chemically unstable and oxidize easily.

The oxidation of fat results in the generation of toxic, harmful substances, which provoke inflammation (7).

Rancidity is also an oxidation process and usually makes the oil smell and taste off. However, if only a part of the oil is rancid and/or oxidized (and most vegetable oils that you buy will be, to an extent), you won’t notice it.

Some of the fat in vegetable oil will come to you already oxidized from the oil’s production process.

Light exposure (on shelves or in your own home) also oxidizes some of it. And finally, heating the oil to high temperatures (when cooking) makes it oxidize as well.

Each of these steps adds to the potentially harmful effects of vegetable oils, and to the toxic substances contained in them. You already see the problem with the unstable chemical bonds of polyunsaturated fats.

#3. Never In Human History Have We Consumed Such A Big Amount Vegetable Oils

In the past century, the availability and consumption of vegetable oils have exploded. Before that, we didn’t have the necessary technology to produce them.

Unlike olive oil or coconut oil, which can be extracted just by mechanically pressing olives or coconut meat, most vegetable oils require complicated technology to produce, which simply wasn’t available to us until the beginning of the 20th century.

Researchers are yet unsure of all the effects that high Omega-6 consumption has on human health, but so far things aren’t looking good, and the most concerning thing is that we’ve never in human history consumed such an imbalanced ratio of Omega-6s to Omega-3s.

What Are The Potential Negative Effects Of Vegetable Oils?

The potential negative effects of consuming lots of vegetable oils are not yet fully researched and well-understood, but there are theories that they provoke obesity, chronic inflammation, and can be a contributing factor to a higher risk of developing heart disease (8).

If you combine them with a diet that consists of predominantly processed foods, high in refined carbs, the effects could be potentially disastrous.

When assessing the risk from excessive vegetable oil consumption, we also need to take into account the fact that these oils are chemically not very stable, and will almost always come to you partially oxidized.

Some of them will be partially hydrogenated, too. This indeed makes them more stable but will mean that they’ll also contain trans fats – and you shouldn’t be having those at all.

Trans Fats

Trans fats are produced from vegetable oils by hydrogenation, which makes them more shelf-stable and also solid at room temperature. They are associated with a higher incidence of cardiovascular disease, type 2 diabetes, and lead to inflammation (9).

This allows food manufacturers to manipulate the texture, visual aspect, taste and shelf life of many products, making them overall more appealing and tastier, and essentially engineering them to be hyperpalatable and extremely easy to eat too much of (speaking in terms of calories), tricking the body’s natural satiety and hunger signals.  

How To Avoid Vegetable Oils?

Now for the good news.

It’s easy to replace vegetable oils in most of the food you’re eating. You just have to make a conscious choice to avoid them, by simply replacing your go-to cooking oil(s), and by not buying any products that contain them.

If you use other types of fat such as olive oil, coconut oil, and butter, for example, this will also improve the taste of the food you’re cooking.

So it’s not even a choice between health benefits and taste that you need to make, the alternatives to vegetable oils are also tastier.

Some of the healthy alternatives to vegetable oils will be more expensive, but then, how long does it take you to go through a bottle of oil?

You don’t need to use a ton of oil or fat when cooking, a little goes a long way.

Even on keto, based on your goals and caloric needs, you still won’t be using huge amounts of oil, especially if you’re already eating fattier cuts of meat, fattier fish, some avocados, nuts, and the like.

Healthy Alternatives To Vegetable Oils:

  • Extra-virgin olive oil
  • Coconut oil
  • Avocado oil
  • Macadamia nut oil
  • Butter and ghee
  • Lard, tallow, etc…
  • Cocoa butter

And lastly, as an Omega-3-rich supplement, you could use fish oil or krill oil.

For high-heat cooking, using coconut oil or ghee is your best bet. These two are very stable and will not degrade easily at higher temperatures.

For sautéeing vegetables, you could use butter, olive oil or avocado oil. For your salad dressings, the best choice would be cold-pressed extra virgin olive oil.

On a ketogenic diet, the quality of the fats you’re eating is extremely important, as fat is an important part of the diet.

You might not necessarily consume more fat than on your previous diet. That depends entirely on what you were eating before and what your current goals and macros are.

Nevertheless, it’s what makes the diet sustainable, together with sufficient protein, so it’s important to opt for the best types of oil and fat and to not just eat any kind of fat.

Eating out can be tricky if you want to avoid vegetable oils completely because most restaurants use them.

Unless they explicitly state it in their menu (for example, “mushrooms in butter”), you should assume that the cooking fat is some sort of vegetable oil, in most cases soybean or canola oil.

In some instances (for example for frying food), vegetable oils are reheated multiple times, which, given how unstable they are, means that an important part of the fat is oxidized. This can have negative effects on health, including a higher risk for atherosclerosis, heart disease, and high blood pressure (10).

You could ask to have your meat prepared in butter or in olive oil. As for salads, ask to have the dressing separately.

Most sauces will contain vegetable oil, so again, if the sauce is a part of a dish, ask to have it separately.

On keto, it’s usually not a good idea to be eating sauces (unless you prepare them yourself), because in most instances they’ll be made with flour and sometimes with sugar, too.

When eating out, always opt for ordering simple food with a few ingredients that would be easy to track and won’t contain hidden carbs or vegetable oils.

Our Conclusion

Vegetable oils are omnipresent in the food industry, however, if you make a conscious effort to avoid them, you’ll see that it won’t be so difficult to do.

Prepare most of your food at home and use some of the many healthy alternatives to vegetable oils. When eating out, ask to have your food cooked in butter or in olive oil, if possible. And last, but perhaps most important, limit highly processed food to a minimum.

Although the effect of the high Omega-6 content in vegetable oils is not yet fully understood, a healthy ratio between Omega-6 and Omega-3 should be of 1:1, up to a maximum of 4:1.

Most vegetable oils’ ratios are much worse than that, and they usually don’t provide any of the added benefits that other oils and fats have, such as containing lots of phytonutrients, antioxidants, or a healthy amount of monounsaturated fat. Overall, vegetable oils will provide you with empty calories and will potentially raise your risks of certain serious health conditions.

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