Over the years there have been many (and contradicting) opinions on the health effects of vegetable oils when used for cooking.
Almost like the whole butter/margarine debate.
Some said it’s healthy, while others said it’s not.
Some said it’s bad for you only when it’s heated above a certain temperature and should preferably be used cold (although this defies the whole point of it being used for COOKING which kind of implies some form of HEAT).
Nevertheless, I’m here today to bring to you a summary of the most important information out there, so we can all decide if we want to use vegetable cooking oil for cooking or not.
So here goes.
In this article I will discuss:
What is vegetable cooking oil?
Let us start at the basics: What is vegetable cooking oil?
The term vegetable oil is a common term that refers to the group of cooking oils that are all made from plant parts.
These could be from fruits, nuts, seeds etc., and include oils like avocado oil, sunflower oil, grapeseed oil, olive oil and canola oil.
These oils are used in cooking to help with heat distribution to prevent burning. They are also used cold, for example in salads.
However, some oils you buy in grocery stores are called “vegetable oil” without specifying which type of oil it is.
In MOST cases, these oils will be soybean oil, otherwise it would be a mix of soybean oil and some other oils, mostly corn oils.
Soybean oil is made by first pressing the soybeans to release the oil inside.
Through centrifugation the oil is separated from the rest of the matter and then refined to remove impurities.
The reason soybean oil is used, is because it’s almost odorless, it’s flavor neutral and it has a high smoke point (234°C/453°F), making it a great choice for high temperature cooking methods like frying.
What is in cooking oil?
Before we get to whether vegetable oil is good or bad for you, we need to get clarification as to what exactly is in oils, which will determine how healthy it is.
Remember, oils and fats are basically the same thing, except for their consistency, which is influenced by the presence and number of double bonds in its chemical structure.
But more about that in a minute.
What is the difference between saturated and unsaturated fats?
Saturated and unsaturated fats differ with saturated fats having no double bonds in their carbon chains, while unsaturated fats have one or more.
This leaves the possibility open for additional hydrogen atoms to attach wherever the double bonds are reduced to single bonds.
The main part of the chemical structure of saturated and unsaturated fats are carbon atoms linked together in a chain.
Then you have hydrogen atoms linked to some of these carbon atoms on the sides.
The catch is, however, that two hydrogen atoms can only link to the sides of a carbon atom in that chain if the bonds between the carbon atom and his two neighboring carbon atoms are single bonds.
If there is a double bond between two carbon atoms, those two carbon atoms can only bind to one hydrogen atom each on their sides.
And that is where the term saturated (with hydrogen atoms) and unsaturated (with hydrogen atoms) comes from.
If there are any double bonds between some of the carbon atoms, there is room for hydrogen atoms to attach wherever those double bonds are reduced to a single bond.
Differences between Saturated, Monounsaturated and Polyunsaturated fatty acids
What is the difference between monounsaturated fat and polyunsaturated fat?
Monounsaturated fats are fats with only one double bond between two carbon atoms somewhere in the carbon chain, while polyunsaturated fats have more than one double bond in the chain.
That means that monounsaturated fats have the capacity to take up another hydrogen atom in its chemical structure, whereas polyunsaturated fats can take up more than one hydrogen atom.
One thing to take note of, is that polyunsaturated fats are more prone to oxidation due to the number of double bonds in the chemical structure. When these fatty acids start to react with oxygen in the atmosphere (oxidation), they start to deteriorate.
What is trans fats?
Trans fats, also called trans fatty acids, are the same as unsaturated fats, having one or more double bonds in the carbon chain.
However, one or more of the double bonds in the trans fatty acid chain is in the trans configuration, whereas these double bonds are in the cis configuration in unsaturated fats.
This causes these trans fatty acids to have a straight structure, almost the same as saturated fats, while unsaturated fats have a bent structure.
This structure also plays a role in the viscosity of fats at room temperature.
Saturated fat with its straight structure is solid at room temperature, trans fats are semi-solid to solid and unsaturated fats are liquid.
Wat are omega-3, omega-6 and omega-9 fatty acids?
Omega-3 and omega-6 fatty acids are polyunsaturated fats that our bodies can’t synthesize by itself, whereas omega 9 fatty acids are monounsaturated fats that our bodies can make itself.
Omega-3 and omega-6 fatty acids, also called essential fatty acids, needs to be ingested. Omega-9 fatty acids, on the other hand, can be produced in the body and that’s also why it’s called non essential fatty acids.
Things to note
One thing to keep in mind is that every one of these fats don’t usually occur on its own in a certain substrate in nature.
Most of the time there is a mix of them all, however, it is the ratios that differ from substrate to substrate.
Animal fats like butter and lard, for example, are much richer in saturated fats than unsaturated fats.
That’s also the reason that they are mostly solid at room temperature.
Plant derived fats like vegetable oils, on the other hand, are richer in unsaturated fats, and that’s also why they are mostly liquid at room temperature.
Hydrogenation is the process where the chemical structure of vegetable oils is changed to form trans fats, which resemble saturated fats, and thus are more solid at room temperature.
Take note that vegetable oils can also contain some trans fatty acids even if they are not hydrogenated.
Which fats are healthy?
The short answer is any fat that is consumed in excessive quantities, is unhealthy, whether that is saturated or unsaturated fats, polyunsaturated or monounsaturated fats, or omega-6 or omega-3 fats.
The consensus was that unsaturated fats (plant-based oils), and more specific polyunsaturated fats, are healthier than saturated fats (animal derived fats).
But even that can be questioned, as can be seen here, here and here.
Butter was portrayed as the big bad guy in the world of fats, and now there are U-turns everywhere.
In fact, in 1965, Harvard professors were paid to play down the link between heart disease and sugar and instead shift the blame to saturated fats!
When it comes to omega-6 and omega-3 fats, there is no clear answer as to what is healthy and what not.
People historically consumed these polyunsaturated fatty acids in a ratio of approximately 1:1, but scientist argue that this has changed a lot with more modern diets and the ratio is now approximately 20:1.
That is almost 20 times more omega-6 than omega-3 fatty acids!
Some scientists think that this higher ratio contributes to chronic inflammation,
while others hypothesize that an increase in omega-6 fatty acids does not increase inflammation.
Frankly, there is no clear indication what the correct intake of omega-3 and omega-6 fatty acids is, and more studies are needed.
There is, however, more data that support the idea that hydrogenated trans fatty acids is less healthy for you and a high intake can contribute to chronic diseases.
At the end of the day hydrogenated oils are processed oils, and processed foods are the ones we should avoid.
What happens when you heat up vegetable cooking oil?
Heating oils and fats increases the rate of oxidation. When oils are oxidized, they release free radicals and other harmful compounds.
As mentioned earlier, the more double bonds in the chemical structure of the oil or fat, the more prone it is to oxidation.
And because vegetable oil is high in these double bonds, it can oxidize readily.
So, when looking for oils or fats to cook with, you need to consider their susceptibility to oxidation, and therefore the composition of its fatty acids.
Olive oil, especially extra virgin olive oil, is a great oil to use and to cook with.
Olive oil is higher in polyunsaturated fats, and the ratio of omega-6 to omega-3 fatty acids is lower, on average 10:1, as opposed to the high 20:1 ratio mentioned earlier.
Olive oil releases less of the harmful compounds over time when heated compared to other oils.
The reason for this is that although olive oil contains some polyunsaturated fats, these are more resistant to the effect of heating.
And on top of that, it tastes great and can also freely be used in salads and dressings cold.
Final thoughts
At the end of the day, moderation of natural products is key.
Avoid processed oils (containing hydrogenated trans fats) and consume oils and fats in moderation and in variety.
Happy cooking!