Best Cooking Oils for Health
Although there are many topics in nutrition that polarise opinion, one of the most debated topics is the best oil or fat to cook with.
Because of this, and the controversy surrounding the best cooking oils, we thought it would be good to write our opinion on the topic to try and clear up any confusion.
The Different Types of Fat
There are 3 different kinds of fat, with these being categorised due to their chemical makeup:
Saturated Fats – In which all of the carbon atoms are ‘saturated’ with hydrogen atoms.
Monounsaturated Fats - Which have a single carbon double bond, meaning they are not saturated with hydrogen atoms.
Polyunsaturated Fats – Which have more than one carbon double bond, so they are even less saturated with hydrogen.
The Different Composition of Common Cooking Fats
There are no fats that are either 100% saturated or unsaturated. All fats contain saturates, monounsaturates and polyunsaturates to varying degrees. Here are some of the most common cooking fats and their fatty acid makeup:
- Coconut oil: 90% saturated, 7% mono, 3% poly.
- Butter: 51% saturated, 21% mono, 3% poly.
- Beef dripping: 50% saturated, 42% mono, 4% poly.
- Lard: 39% saturated, 45% mono, 11% poly.
- Goose fat: 33% saturated, 56% mono, 11% poly.
- Olive oil: 15% saturated, 74% mono, 11% poly.
- Rapeseed (canola) oil: 7% saturated, 61% mono 32% poly.
- Sesame oil: 14% saturated, 40% mono, 42% poly.
- Soybean oil: 15% saturated, 23% mono, 62% poly.
- Corn oil: 13% saturated, 28% mono, 59% poly.
- Sunflower oil: 12% saturated, 15% mono, 73% poly.
It is well-known that saturated fats are the most stable when cooked at high temperatures, whilst monounsaturated fats are also quite stable. However, polyunsaturated fats are quite unstable. This means that oils high in polyunsaturated fats such as sunflower oil can undergo some quite alarming changes when subject to heat; a topic we’ll address in more detail next.
The Smoke Point of Cooking Oils
An important factor when selecting healthy cooking fats is the ‘smoke point’. This is the temperature at which the oil begins to smoke. For cooking at high temperatures, the best fats therefore have a high smoke point, to avoid the production of carcinogens.
Here are the smoke points of numerous common cooking fats:
- Extra virgin olive oil: 160°C
- Butter: 177°C
- Coconut oil: 177°C
- Goose fat: 190°C
- Lard: 190°C
- Rapeseed (canola): 204°C
- Sesame oil: 210°C
- Beef dripping: 215°C
- Sunflower oil: 227°C
- Corn oil: 232°C
- Soybean oil: 232°C
Typically, as the above list demonstrates, the lighter the colour of the oil the higher the smoke-point.
Oils that are highly refined have had the polyphenols, antioxidants and vitamins removed. These nutrients are very delicate and prone to damage from heat. For this reason, cold pressed oils such as flaxseed are very healthy, but should not really be used for cooking at all and should instead be confined to dressings and dips.
Similarly, as extra virgin olive oil has a low smoke point, it should also be used for dressings and dips or cooking at low temperatures.
As most deep frying is done at a temperature of 170-180°C, this suggests that lard, goose fat, beef dripping and refined seed oils are suitable for this style of cooking.
However, in the next section we will uncover evidence as to why this may not be the case…
The Issue with Vegetable Oils
As we have just discovered, when cooking at high temperatures, it is best to use an oil or fat with a high smoke point. However, you also want it to be stable, so the fats do not oxidise and form harmful chemicals.
One study published in the journal Food Chemistry assessed the formation of dangerous acrylamide molecules in different cooking fats. The researcher’s heated lard (high in monounsaturates), ghee (high in saturates) and soybean oil (high in polyunsaturates) to 180°C and then assessed their chemical composition.
Alarmingly, it was found that soybean oil created almost 7 times more acrylamide than lard and over 11 times that of ghee. This is a big concern given the amount of polyunsaturated vegetable oils used for cooking. Furthermore, the latest statement from the Food Standards Agency reports that:
“Laboratory tests show that acrylamide in the diet causes cancer in animals. Scientists agree that acrylamide in food has the potential to cause cancer in humans as well. We recommend that the amount of acrylamide we all consume is reduced”.
To make matters worse, polyunsaturated vegetable oils are very high in the omega 6 fat linolenic acid. Although this fat is essential to health, we only need a small amount of it. The increase in vegetable oil consumption has seen an explosion in omega 6 intake, whilst at the same time, a decrease in essential omega 3 fats.
Many experts are in agreement that humans evolved on a diet with an omega 6:omega 3 ratio of between 1:1 and 4:1. However, a typical western diet now provides between 16:1 and 20:1.
To maintain good health it is important to keep inflammation levels under control. Acute inflammation can certainly be healthy, as it can help to fend against pathogens and destroy unhealthy cells. However, chronic inflammation is certainly something to be avoided as it has a role in some of the most common diseases.
As omega 6 fats stimulate pro-inflammatory pathways within the body and omega 3 anti-inflammatory ones, you can begin to see why it is important to have a healthy balance. Limiting the proportion of processed foods and vegetable oils within the diet, combined with an increased consumption of flaxseeds, walnuts and oily fish can therefore improve your health.
So, to summarise the information we have covered so far we should preferably use cold pressed oils such as flaxseed and extra virgin olive oil for dressings or cooking at low temperatures and fats with a higher percentage of saturated fats for cooking at high temperatures.
Saturated Fat and Health
The question you’re probably wondering now is: “Isn’t saturated fat bad for health”?
Well, the assertion that saturated fat causes heart disease (the diet-heart hypothesis) has come under massive scrutiny due to its flawed evidence. In the 1950’s a researcher called Ancel Keys oversaw the seven countries study, which analysed the link between dietary fat, cholesterol and deaths from heart disease.
The major flaw of this study is that Keys left out countries from his analysis that would not support his theory. In a nut shell he cherry picked the data. What followed this was a number of other poorly designed and smaller studies that again provided flawed evidence.
Alarmingly, the seven countries study was a major influential factor in the first dietary guidelines for countries such as the USA, Canada & the UK despite its methodological issues. These dietary guidelines, which have been adopted by most other countries, promote a high carbohydrate, low fat diet. What’s more it is recommended that saturated fat contributes no more than 10% of your total calorie intake, with polyunsaturates recommended as a substitute.
Whilst studies such as the seven countries study can merely provide an association, the highest level of scientific evidence comes from randomised control trials (RCT’s) which allow us to see cause and effect. What is concerning is that less than 2500 people were studied in RCT’s on a low fat diet before influencing the first dietary guidelines. All of these participants were men who suffered from heart disease. In other words, hundreds of millions of people were subject to dietary recommendations that had not even been assessed in women, or people without heart disease.
Subsequent high quality research (RCT’s) and meta-analysis of RCT’s has provided strong evidence to contradict the diet-heart hypothesis. A meta-analysis of randomised control trials published in 2017 concluded that:
“Available evidence from adequately controlled randomised controlled trials suggest replacing saturated fats with mostly omega 6 polyunsaturated fats is unlikely to reduce Coronary Heart Disease (CHD) events, CHD mortality or total mortality. The suggestion of benefits reported in earlier meta-analyses is due to the inclusion of inadequately controlled trials. This has implications for current dietary advice.”
Another meta-analysis published in the British Medical Journal a year earlier concluded with this statement:
“Available evidence from randomized controlled trials shows that replacement of saturated fat with linoleic acid effectively lowers serum cholesterol but does not support the hypothesis that this translates to a lower risk of death from coronary heart disease or all causes”.
So, although replacing saturated fat with polyunsaturated vegetable oils reduces total cholesterol levels, this hasn’t been shown to decrease heart disease deaths.
Natural fats that contain a high percentage of saturates such as butter and lard also contain some essential nutrients. For example, butter is a rich source of vitamin A and contains appreciable amounts of vitamin D. Similarly, lard from pigs that have had good exposure to sunlight is very rich in vitamin D.
Although we don’t think it is wise to eat masses of saturated fat, the evidence is pretty clear that saturated fat is not harmful and is fine to consume in moderation. This type of fat should certainly be considered when frying foods at high temperatures – something we should only do occasionally.
How to Store Oils
An important consideration is how to store your fat or oil. As we have found, temperature can cause oils to go rancid. For this reason, it is best not to store oils next to sources of heat (cooking hobs, kettles etc.). Similarly, oils can turn rancid when exposed to light and oxygen. So, storing oils in a dark place such as a cupboard with the lid on tightly is best in most cases.
Certain oils, such as flaxseed, are very delicate and best stored in the fridge. This helps to keep them fresher for longer. If in doubt, always read the label on the bottle.
The best cooking fat is certainly a hotly debated topic with many factors at play. Hopefully this piece has helped to clear up any confusion and has provided you with the knowledge of which oils/fats are best to use and when.
As we have covered a lot of information, we thought it would be useful to finish by summarising the key points of the article:
- All fats contain a mixture of saturated, monounsaturated and polyunsaturated fatty acids. Saturated fats are the most stable when heated, monounsaturated fat are fairly stable and polyunsaturated fats quite unstable.
- Highly refined vegetable oils have had many of their natural qualities removed. Due to this, they have a high smoke point which means they are widely used for cooking at high temperatures.
- Research has also shown that when heated, polyunsaturated vegetable oils can produce harmful compounds to a much greater extent than oils higher in saturates and monounsaturates.
- Regular consumption of vegetable oils high in omega 6 can perturb the omega 6:3 ratio in the body, which is linked to a variety of healthy complications.
- For sauces, marinades or cooking at low temperatures, cold pressed extra virgin oils are a good choice to provide healthy fats and antioxidants. Fats high in saturates are good for cooking at high temperatures.
- The traditional diet-heart hypothesis which has influenced dietary guidelines around the globe is based on flawed evidence which has not stood up to modern scrutiny. This has created a food environment that encourages polyunsaturates and discourages saturates.
- Although saturated fat often raises cholesterol (both LDL & HDL), there is no high quality scientific evidence to show this increases deaths from cardiovascular disease when replacing polyunsaturated vegetable oils.
- For good health, frying or deep frying should only be done occasionally and not be a primary method of cooking.