Fat, cooking oils, and health
For the past 50 years, fat was associated with harmful health effects, but the paradigm is gradually changing. Researchers are reviewing previous studies and guidelines regarding different recommendations on saturated fats and heart health. This article explores fats, the research regarding saturated fats and heart health, different oils and solid fats for cooking, and things to consider when selecting your cooking oils or solid fats.
FATS or FATTY ACIDS
Fats, or fatty acids, are chains of different quantities of carbon atoms with variable quantities of hydrogen atoms. When they have less hydrogen than their maximum capacity, they are called unsaturated fats and have double bonds in between some carbons, also known as polyunsaturated fats, monounsaturated fats, or trans fats. A double bond is unstable when in contact with oxygen, heat, or light, leading to possible oxidization and the creation of harmful molecules, which lead to inflammation when ingested.1 While monounsaturated and polyunsaturated fats are generally considered healthy when consumed, storage and the way they are consumed are important to consider.
Image: Structure of different types of fats
Dietary fats consist of a mix of all types of fats in variable concentrations. Oil or a solid fat are named by the fat having the highest concentration.
E.g. Olive oil is a monounsaturated fat, having 75% of monounsaturated fat, 14% of saturated fat, and 11% of polyunsaturated fats. Coconut oil is a saturated fat (91%), but also contains smaller concentrations of monounsaturated fats (7%) and polyunsaturated fats (2%).
Here is a chart illustrating the concentration of saturated, unsaturated, and polyunsaturated fats per oil or solid fat type.
CHART: Fats ratio per oil or solid fat type
FATS AND HEALTH
Before we jump into cooking, let's explore the studied effects of different types of fats on the human body. We once believed that fats made you fat. That is wrong. Also, fats were initially thought to be harmful because of their possible risk of increasing LDL (bad cholesterol), and/or total cholesterol. High levels of LDL have been associated with heart diseases. Note that a high level of LDL alone is meaningless. Levels of LDL should always be associated with HDL (good cholesterol levels), the ratio, apolipoprotein, and more.
THE GOOD, THE BAD AND
THE CONTROVERSIAL FATS2
Fats are a high-energy food source, they help vitamin and mineral absorption and reduce inflammation. 3
THE BAD FATS: Trans fats
A byproduct of hydrogenation (turning healthy oils into solids and preventing them from becoming rancid)
No known health benefits
An unsaturated fat
Banned in the United States and many other countries
Mostly found in cookies, pastries, French fries
Increases LDL and lowers HDL
Create inflammation, which can lead to heart diseases, stroke, diabetes, and chronic illnesses
THE CONTROVERSIAL FATS: Saturated fats
Unclear data regarding harm or safety
Solid at room temperature (e.g. butter, coconut oil)
Mostly found in red meat, whole milk, cheese, coconut oil
Can increase total cholesterol, and some limited data seem to balance towards more increase of LDL
While many studies seem to have linked saturated fats with heart diseases,4 more recent data seem to express a lack of clear link.
THE GOOD FATS: Monounsaturated and polyunsaturated fats
Monounsaturated fats are found in olive oil, peanut oil, canola oil, avocados, most nuts, sunflower oil
Polyunsaturated fats are found in corn oil, sunflower oil, safflower oil
Essential fats
Polyunsaturated
Omega-3 and omega-6 fatty acids
Monounsaturated
Omega-7 and omega-9 fatty acids
Mostly found in vegetables, nuts, seeds, and fish
Liquid at room temperature (e.g. olive oil)
THE STUDIES & SATURATED FAT
The recommendation that dietary saturated fats increase total cholesterol, and then increase the risk of coronary heart disease mortality was refuted in a commentary in The American Journal of Medicine in 2020. The authors mention that the study published in 1967 by Dr. Mark Hegsted and two other Harvard doctors, claiming that saturated fats are harmful, was hiddenly funded by the Sugar Association. The article written in 1967 minimizes the link between sugar and heart health while increasing the link between saturated fats and heart diseases.
The American Heart Association (AHA) was also refuted in a recent Review in June 2020 in the Oxford Nutrition journal. The recommendation of the AHA regarding limiting saturated fat (SFA or saturated fatty acid) and replacing it with polyunsaturated fat to reduce the risk of heart disease was solely based on 4 clinical trials with methodological flaws and unmet predefined inclusion criteria. The Oxford Nutrition Review authors reviewed the recommendation by conducting a meta-analysis including 19 meta-analyses, 9 observational studies, and 10 randomized controlled trials. Oxford review authors state that the evidence regarding limiting SFAs for heart disease prevention may be overstated and should be reevaluated.
Cochrane also conducted a review regarding the statement that saturated fat is harmful. Cochrane review found little to no effect of reducing saturated fat on all-cause mortality, cardiovascular mortality, or non-fatal myocardial infarction. It was also unclear whether saturated fats had an effect on cancer mortality, diabetes, myocardial infarction, strokes, and more.
Many scientists mention that saturated fats are harmful, while others claim that they are not. Some also claim that the source of saturated fat may be the issue. Basically, we’re unsure if what we have been doing for the past 50-60 years was or is still accurate. We thought fat made us fat and unhealthy, but we’re starting to realize that sugar is probably the bad guy.
So, which fat should you consume? In my opinion, eliminate trans fats from your diet, have a balanced consumption of other types of fats.
FAT SOURCES MATTER
Myth or Reality?: Cooking with Olive Oil can produce harmful molecules, and should not be used when cooking at high heat.
It’s a bit complicated. Some authors state that it is safer to cook with saturated fats (coconut oil, butter, ghee butter) because they are saturated and more stable when heated. In contrast, unsaturated fats have a double bond, making them more reactive when heated and in contact with oxygen or light.
Most vegetable oils are polyunsaturated or monounsaturated fats. Such vegetable oils or canola oils have been labeled unsafe to cook because they oxidize when heated and form dangerous molecules that can trigger inflammation. Most vegetable oils, unlike olive oil, are highly processed high in omega-6. Too much omega-6 can lead to inflammation. Vegetable oils high in omega-6 include soybean oil, corn oil, cottonseed oil, sunflower oil, peanut oil, sesame oil, and rice bran oil.
Saturation or smoking point?
Some authors look at oil or fat saturation for stability, while others consider smoking points.
What is a smoking point?
A smoking point is a temperature at which the fat starts to break down, release free radicals, lose some nutritional value and give food an unpleasant taste. They become potentially unhealthy.5
SMOKING POINTS PER TYPE OF FAT/OIL
Peanut oil | 450°F |230°CCorn oil | 450°F | 230°CSunflower oil | 440°F | 225°CVegetable oil | 400°F - 450°F | 205°C - 230°CCanola oil | 400°F | 205°CGrapeseed oil | 390°F | 195°CAvocado oil | 375°F - 500°F | 190°C - 205°CSesame oil | 350°F - 410°F | 175°C - 210°CButter | 350°F | 175°CCoconut oil | 350°F | 175°CExtra Virgin Olive Oil | 325°F - 375°F | 165°C - 190°C
Some scientists and authors mention that the smoking points should assess which oil is safer to use. It would be best if you did not cook at a temperature higher than the smoking point. They even suggest different oils for different types of cooking, based on smoking points.
For example:
For high-heat frying and stir-frying, use peanut, sesame, or soybean oils.
For sauteing at medium-high heat, use avocado oil, corn oil, canola oil, or olive oil.
Use any oil for salad dressing, but the ones with a low smoke point, such as flaxseed oil, pumpkin seed oil, or walnut oil, should mostly be used only for that.
So, do we use smoking points or fat saturation? Let’s explore olive oil stability as an example first.
OLIVE OIL STABILITY
Olive oil is known for its health benefits and has shown a protective effect on LDL levels.6 It has been praised for a long time for its benefits, anti-cancer, anti-inflammatory, antioxidant property, and more.7, 8
There are many different types of olive oil, and quality is essential. Storage is also crucial, and we’ll tap into this in a second. Virgin oils are cold-pressed raw oils. Some processes will eliminate some components and may make the oil less stable. Extra virgin olive oil (EVOO) goes through less processing than pure olive oil, making it healthier and more stable. Olive oil is a monounsaturated fat high in polyphenols and tocopherols, antioxidants that protect the oil from oxidizing and creating harmful molecules. Since it contains only 1 double bind, it is more stable than other polyunsaturated fats. 9 Some dated studies show the stability of olive oil when heated,10 but more recent studies mention that olive oil's stability is decreased with temperature and heating duration increase.
An article published in the Journal of the American Oil Chemists' Society in 2017 seems to state that frying causes physicochemical changes in olive oil, leading to important human health consequences. The reaction increases free acidity making the oil harder to digest. They also state that an increase in oxidative products due to oxidative stress contributes to atherosclerosis, which seems contradictory to olive oil's benefits. Also, oil oxidation produces lipid aldehydes with harmful effects on human health by inducing apoptosis and necrosis. The authors of the article conclude that high heat (240°C) and heating duration(2 hours) significantly influence extra virgin olive oil physico-chemistry.
Extra Virgin Olive Oil has a smoking point of 165°C - 190°C, and according to this previous study, heating higher than 240°C can lead to the production of harmful molecules. It would be safe to say that cooking with olive oil can be completely safe, depending on heating temperature and duration. This fact should not discourage the consumption of olive oil, being delicious and healthy.
HIGH SMOKING POINT OR SATURATED FATS?
As for other cooking oils or solid fats, it will depend on what you are cooking. We can agree that healthy oils can be used for low-temperature cooking. If you cook at a high temperature, opting for saturated fats like coconut oils or butter seems safest. For moderate-temperature cooking, olive oil, avocado oil, or coconut oil are good choices.
STORING OILS
Storage is vital for oils, and contact with air, heat, and light should be avoided. Exposure to the oil will lead to loss of nutrients. Polyunsaturated oils (flaxseed, grapeseed, and walnut) would be stored in the fridge for longer shelf life. Never buy oils that are not in a dark container. Store your cooking oils in a cool and dark area.
Remember: dark & cool
A WORD ON CLIMATE CHANGE AND FOOD QUALITY
A study found that high environmental temperatures were also associated with reducing olive oil yield and quality. This also illustrates the impact of global warming on our soil and food quality.11
CONCLUSION
Key points to remember:
Eliminate trans fats;
Eat monounsaturated and polyunsaturated fats;
Saturated fats seem healthy, but the product quality is essential;
Select the cooking oil/solid fat, depending on your recipe (heat and cooking duration);
Olive oil seems safer at a lower temperature;
Opt for saturated fats with high smoking points for cooking at high temperature;
Select good quality oils;
Storage is crucial, remember, cool and dark;
At this point, the safety regarding the consumption of vegetable oils remains unclear. It also depends on the amounts consumed. If your goal is eating less processed foods, the best is to avoid them;
Everything is about balance.
For your health,
-Dr. Stephanie E.