Extra virgin olive oil (EVOO) in general is good for us. But how about cooking with olive oil? Some common questions you may have, are:
- Is cooking with olive oil bad for you?
- Are the health benefits of olive oil diminished after it has been cooked?
- Does the smoke point matter?
- Should I use another oil when cooking?
Background on Some of the Typical Benefits of EVOO
The leading cause of death in 2020 was ischaemic heart disease-causing 49% of overall deaths.
Ischaemic heart disease occurs when a high amount of cholesterol builds up inside blood vessels. This accumulation causes cholesterol to get trapped inside arterial walls. The body sends white blood cells to the area, causing an increase in inflammation. Over time, this builds up causing what’s known as atherosclerosis.
Narrowing arterial walls can make it challenging for the heart to pump blood around the body, causing an increase in blood pressure and strain on the heart. High blood pressure can cause the plaque to break off and get stuck in small blood vessels, leading to a stroke or heart attack.
A pro-inflammatory state can also increase insulin resistance, often associated with type 2 diabetes.
Thereby it’s important to maintain low blood cholesterol and inflammation inside of the body to decrease any risk of this occurring.
Now, where does olive oil come into all of this?
In 1979, the Mediterranean-style diet was identified for its ability to decrease cardiovascular disease even for people with larger bodies. EVOO is one of the main components of the Mediterranean diet, therefore its health benefits were further researched.
A meta-analysis on the Mediterranean diet looked at 50 studies, with 534,906 participants who found that EVOO in particular had a high level of monounsaturated fats that replace the saturated fat and thus manage blood cholesterol levels. Its high levels of polyphenols also prevent any of the healthy blood lipids from undergoing oxidative stress (cellular damage).
An 8-week study on individuals with type 2 diabetes mellitus (T2DM) showed that adding 25mL of extra virgin olive oil to their regular diet decreased fasting blood glucose levels (BGL), HbA1C, and BMI. Though, it’s hard to know if the improvements in fasting BGL and HbA1C were due to the reduction in weight.
What Happens When We Heat Olive Oil?
Extra virgin olive oil is high in:
- Monounsaturated fats
- Vitamins and minerals
- Antioxidants (polyphenols and tocopherols)
Tocopherols (Vitamin E) and Polyphenols are a type of antioxidants that prevent the body from undergoing oxidative stress. Oxidative stress damages healthy cells, causing things like aging, cancer, coronary heart disease and inflammation.
When olive oil is heated, we’ve seen that its own polyphenols prevent its monounsaturated fats from breaking down.
- Monounsaturated fats (MUFA) have one carbon bond (double bond). Its chemical structure makes it liquid at room temperature and solid when chilled. This double bond stabilises the oil, allowing it to withstand high amounts of heat.
- Polyunsaturated fats (PUFA) have multiple double bonds (hence the name ‘poly’). These bonds break down easily when exposed to high amounts of heat, limiting their ability to withstand high amounts of heat.
- Saturated fats (SFA) have no carbon bonds, their sturdy molecular structure makes them solid at room temperature. You’ll see shortly that they can usually withstand higher amounts of heat, however, these fats also increase LDL and cholesterol inside the blood.
Below are 4 of the most common oils used when cooking. Besides them are the types of fats that they are made up of.
A study was done on coconut, safflower, canola and extra virgin olive oil. It heated the oils to 180 º, 210 º, 240 º, and 270ºover 6 hours. It found that as time increased so too did the emission of volatile gases (aldehydes). Aldehydes are reactive species that can be toxic to the body if consumed in high doses.
Once the oil reached the smoke point volatile production significantly increased, this is shown in the image below.
The volatile production of EVOO starts off relatively high once it hits 180º, it has a smoke point of 190 º so this is to be expected. You can see though, that as the temperature of the oil increased, EVOO volatile production remained steady in comparison to the other oils.
This may flag as a concern, thinking that the volatiles are quite high, even at 180 º. But the human body produced several aldehydes metabolising enzymes that work to break them down into less harmful and easily excreted products. Allowing the body to maintain a healthy state.
If this is still a concern, another study recommended that canola oil should be used when cooking above 180 º because it produced the least number of aldehydes. However, EVOO should be used for anything below those temperatures.
So that raises the question, will you be cooking above 180 º enough to stock your cupboards with 2 types of oil? Or are you happy with consuming moderate amounts of aldehydes knowing that your body will be able to excrete them?
The smoke point of an oil is defined as the temperature that which oil begins to break down and continuously releases a bluish smoke. Once the oil reaches its smoke point, glycerol and free fatty acids break down into aldehydes, ketones, and alcohols. These can be harmful to the body and are also an unpleasant flavour to consume.
The smoke point is more so dependent on the amount of FFA present. The chain length of the lipid plays a significant role in the body. As we’ve seen in the research that high amounts of FFA (short-chain) contribute to insulin resistance and inflammation inside of the body, which can be an issue.
Olive oil has a smoke point of around 190-270 º
To put this into perspective, I collated a list of standard cooking methods alongside their temperatures. These are as follows:
- Boiling – 100 º
- Steaming – 100 º
- Roasting – 180 º
- Microwaving – 100 º
- Deep frying – 170-180 º
- Fry Pan – 200-220 º
None of these methods typically reach the lower end of EVOO smoke point.
Does Oil Quality Change When Heated?
One study monitored extra virgin olive oil quality over 36 hours. Yep, 36!! They maintained the temperature at 180 º and found that the tocopherols and polyphenols did reduce over time. However, the remaining nutrients stayed intact.
Deep frying EVOO obviously comes close to reaching the 190º smoke point. However, even when fried for 24-27 hours EVOO potent amounts of antioxidants withstood the high amounts of heat. It had significantly less oxidation and hydrolysis when compared to vegetable oils.
Pan-frying EVOO at 120 and 170 decreased the polyphenols by 40% and 75%, respectively. They heated the oil for 15 to 60 minutes, this showed no change to the polyphenol content.
Showing that extra virgin olive oil will maintain its high nutrient profile/quality when exposed to high amounts of heat for an extended period of time.
But How Does It Affect Human Health When Cooked?
As mentioned, EVOO can decrease inflammation and assist in increasing insulin sensitivity. So, another study has looked at 17 women, 12 were classified as BMI obese and insulin-resistant, and the other 5 were classified as a healthy BMI range. They received two different meals, one with cooked olive oil and the other uncooked, they measured glucose, insulin, C-peptide, and triglycerides every 30 minutes for 3 hours.
The results showed no difference in lean individuals. Though, it did show that insulin and C-peptide responses were reduced after consuming the meal fried in extra-virgin olive oil for the obese, insulin-resistant women.
Yes, it’s a small study, based on short-term outcomes.
Looking at larger research, a 2015 systematic review established that frying food in standard vegetable oils can increase the risk of chronic disease, however, the opposite occurred when using EVOO.
If microwaving is your cooking method of choice, then this might also be good news. A study cooked EVOO for 10 minutes found that the oil degradation was lower than all other forms of heating and that the polyphenols were not affected.
Can you cook with olive oil?
Short answer, yes.
The compiled evidence shows that in order to preserve the bioactive components of EVOO heating time should be kept to a minimum. Though, some of the research has shown that improved health outcomes are associated with cooking with EVOO.
The health benefits of heated or room temperature EVOO continues to outweigh any other form of vegetable oil.
I don’t know about you, but I don’t usually cook above 180 º which is what many of these studies have done.
So, if you’re the same, then I would recommend cooking with olive oil.