Rapeseed oil

Rapeseed oil is a vegetable oil that can be found in countless foods. Many people have banned rapeseed oil from their diet due to concerns about its health effects and production methods. So the question is whether it is better to use or avoid rapeseed oil. This article will look at this question from a scientific perspective.

What is rapeseed oil?

Rapeseed (Brassica napus L.) is an oilseed crop that has been bred through cross-breeding. In the 1960s, scientists from Canada bred an edible version of the rapeseed plant that contains only small amounts of erucic acid and bitter substances that are harmful to health. Prior to this, rapeseed was primarily used for the production of lamp oil, lubricants and soap. Although these new rapeseed varieties do not look any different from their predecessors, they contain different nutrients and their oil is suitable for human consumption. Since the breeding of these new rapeseed varieties, plant breeders have developed many different varieties that are characterized by a higher quality of their seeds and this has led to a boom in rapeseed oil production. Many canola varieties have been genetically modified to improve oil quality and increase the plant's resistance to herbicides (1). About 90% of canola varieties grown in the US are genetically modified. These modified canola varieties are used to produce canola oil and canola meal, which is primarily used as animal feed. Rapeseed oil can also be used as an alternative for diesel fuels and is also a component of plasticizers used in products such as car tires.

How is rapeseed oil produced?

Several steps are necessary for the production of rapeseed oil. This process includes the following steps:

Cleaning the seeds: The rapeseed is separated and cleaned to remove impurities such as plant stalks and dirt.
Seed conditioning and flaking The seeds are heated to around 35 degrees Celsius and then processed into flakes by roller mills, which destroy the cell walls of the seeds.
Cooking the seeds: The seeds are heated to 80 to 105 degrees Celsius for 15 to 20 minutes in a series of steam-heated stoves.
Pressing: Next, the cooked, flaked rapeseeds are pressed in a series of presses. This action removes about 50 to 60% of the oil from the flakes - the rest can then be extracted by other methods.
Solvent extraction: The remaining seed flakes are further broken down by using a chemical called hexane to obtain the remaining oil.
Removal of the solvent: The hexane is then removed from the oil by heating the oil to 95 to 115 degrees Celsius.
Processing the oil: The extracted oil is refined using various methods such as steam distillation, the use of phosphoric acid and filtration through acid-activated clay.

In addition to this, rapeseed oil, which is used to make margarine and shortening, undergoes a hydrogenation process - a process in which hydrogen molecules are pumped into the oil to change its chemical structure. This process makes the oil solid at room temperature and extends shelf life, but also creates artificial trans fats, which are different from the natural trans fats found in foods such as dairy and meat products (1).

Artificial trans fats are harmful to health and have been linked to heart disease, which is why many countries are promoting a ban on their use in food (2).

Summary: Rapeseed oil is a vegetable oil obtained from the rapeseed plant. The production of rapeseed oil involves the use of synthetic chemicals to help extract the oil.

Nutrient content

Like most other oils, rapeseed oil is not a good source of nutrients. 1 tablespoon (15 ml) of rapeseed oil provides:

Kcal: 124
Vitamin E: 12% of the daily requirement
Vitamin K: 12% of the daily requirement

Apart from vitamin E and K, rapeseed oil contains no other vitamins or minerals.

Fatty acid composition

Rapeseed oil is often touted as one of the healthiest oils due to its low saturated fat content. The fatty acid composition of rapeseed oil is as follows (3):

Saturated fats: 7%
Monounsaturated fats: 64%
Polyunsaturated fats: 28%

The polyunsaturated fats in rapeseed oil include 21% linoleic acid - an omega-6 fatty acid - and 11% alpha-linolenic acid (ALA), a type of omega-3 fatty acid derived from plant sources (4).

Many people - and especially people who follow a plant-based diet - rely on ALA to increase their levels of the omega-3 fatty acids DHA and EPA, which are crucial for heart and brain health. However, even though the human body can convert ALA into DHA and EPA, scientific research shows that this process is very inefficient. However, ALA also has some benefits of its own, as it can reduce the risk of bone fractures and protect against heart disease and type 2 diabetes (5, 6). It is important to note that the heating methods used in the production of rapeseed oil, as well as high heating during frying and roasting, have negative effects on polyunsaturated fatty acids such as ALA. In addition, high heating during processing converts a small proportion of the unsaturated fats in the oil - especially polyunsaturated fats - into artificial trans fats, which further reduces the amount of omega-3 fatty acids contained (7). Artificial trans fats are toxic even in small amounts, which has led the World Health Organization (WHO) to call for the global elimination of artificial trans fats in food by 2023 (8).

Summary: Apart from small amounts of vitamin E and K, rapeseed oil is not a good source of nutrients. In addition, canola oil may contain small amounts of trans fats, which are harmful to health.

Potential disadvantages

Rapeseed oil is the second most widely grown oil crop in the world and its use in food continues to grow. While canola has become one of the most popular sources of fat in the commercial food industry, concerns about its health effects have increased.

Rapeseed oil is rich in omega-6 fatty acids

One of the drawbacks of rapeseed oil is its high content of omega-6 fatty acids. Just like omega-3 fatty acids, omega-6 fatty acids are essential for health and important functions of the body. However, the modern diet tends to be extremely high in omega-6 fatty acids, found in many processed foods, while being low in omega-3 fatty acids from whole foods, leading to an imbalance that promotes inflammation. While the healthiest omega-6 to omega-3 ratio is 1:1, the typical Western diet tends to have a ratio of 15:1 (9). This imbalance has been linked to a number of chronic diseases such as Alzheimer's, obesity and heart disease (10, 11, 12). The omega-6 to omega-3 ratio of rapeseed oil is 2:1, which may not seem particularly bad. However, because canola oil is found in so many foods and contains more omega-6 than omega-3 fatty acids, it is considered one of the main sources of omega-6 fatty acids. To create a more balanced ratio, you should replace processed foods rich in rapeseed oil with natural sources of omega-3 in the form of natural foods such as oily fish.

Rapeseed oil is often made from genetically modified rapeseed

In genetically modified foods, the genetic material of the plant has been altered by adding or removing certain qualities (13). For example, many crops such as corn and canola have been genetically modified to make them more resistant to herbicides and pests.

Although many scientists consider genetically modified foods to be safe, there are widespread concerns about these crops on the environment, general health, contamination of other crops, property rights and food safety. Over 90% of canola crops grown in America and Canada are genetically modified.

Although genetically modified foods have been approved for human consumption in many countries, little data exists regarding potential health risks, leading many people to avoid these foods.

Rapeseed oil is highly processed

The production of rapeseed oil involves high heat and the use of chemicals. Canola oil, which is considered a chemically refined oil, goes through many processing steps such as bleaching and deodorization, which involve chemical treatment (14). Refined oils including canola oil, soybean oil, corn oil and palm oil are also referred to as RBD (refined, bleached and deodorized) oils. These processing steps reduce the nutritional content of these oils in terms of essential fatty acids, antioxidants and vitamins (15, 16, 17). Although unrefined, cold-pressed canola oils are available, most canola oils on the market are highly processed products that lack the antioxidants found in unrefined oils such as extra virgin olive oil.

Summary: Most rapeseed oils are highly processed, genetically modified varieties. In addition, rapeseed oil is a rich source of omega-6 fatty acids, which could contribute to inflammation if consumed in large quantities.

Can rapeseed oil damage your health?

Even though rapeseed oil is one of the most widely used oils in the food industry, there are comparatively few long-term studies on its effects on health. Furthermore, many studies showing its alleged health benefits have been funded by the rapeseed oil industry (18, 19, 20, 21, 22).

Having said this, it should not go unmentioned that there is evidence that canola oil may have negative effects on health.

Increased inflammation

Several animal studies have linked canola oil to increased inflammation and oxidative stress. Oxidative stress refers to an imbalance between harmful free radicals - which can cause inflammation - and antioxidants, which delay or prevent free radical-induced damage. In one study, rats fed a diet consisting of 10% canola oil experienced a reduction in levels of several antioxidants and an increase in levels of "bad" LDL cholesterol compared to rats fed soybean oil instead of canola oil. In addition, canola oil significantly reduced lifespan and led to significant increases in blood pressure (23).

Another study conducted with rats showed that compounds formed during the heating of rapeseed oil can increase certain inflammatory markers (24).

Influence on memory performance

Studies carried out on animals also suggest that rapeseed oil could have a negative impact on memory performance. A study carried out with mice came to the conclusion that a long-term diet rich in rapeseed oil resulted in a significant deterioration in memory performance and a substantial increase in weight (25).

In a year-long human study, 180 older adults were randomly assigned to a group with a diet rich in refined oils, including rapeseed oil, or a group in which all refined oils were replaced with 20 to 30 ml of extra virgin olive oil per day. Improved brain function was observed in the subjects in the olive oil group (26).

Influence on heart health

Even though rapeseed oil is advertised as a heart-healthy fat, some studies cast doubt on this claim.

In a 2018 study, 2,071 adults reported how often they used certain types of fat for cooking. Among the overweight or obese people in the study, those who habitually used canola oil for cooking had a higher risk of metabolic syndrome than subjects who rarely or never used canola oil (27). Metabolic syndrome refers to a cluster of health problems - including high blood pressure, excessive belly fat, high blood sugar levels and high cholesterol and triglyceride levels - that occur together and increase the risk of heart disease. The results of the study contradicted the findings of an industry-funded review that linked canola oil with positive effects on heart disease risk factors such as total cholesterol levels and levels of bad LDL cholesterol (18). It is important to note that many of the studies suggesting benefits of canola oil for heart health used less highly refined canola oils or unheated canola oil - not the highly processed, refined types commonly used for high-heat cooking (28, 29, 30, 31, 32, 33). In addition, while many health organizations are pushing for the replacement of saturated fats with unsaturated vegetable oils such as canola oil, it is unclear whether this is actually beneficial for heart health. An analysis of 458 men found that those who replaced saturated fats with unsaturated vegetable oils had lower levels of 'bad' LDL cholesterol compared to the control group, but had significantly higher mortality rates and higher rates of heart disease and coronary heart disease (34).

In addition, a recent review concluded that replacing saturated fats with vegetable oils is unlikely to reduce rates of heart disease, death from heart disease or overall mortality from all causes (35). However, further research on canola oil and heart health is needed to draw conclusive conclusions (36, 37).

Summary: Some studies suggest that canola oil may promote inflammation and have negative effects on memory and heart health.

Alternative oils for cooking

It's clear that more research is needed to fully understand the health effects of canola oil. In the meantime, you can turn to many other oils whose benefits are supported by scientific research. The following oils are heat-stable and can replace canola oil in cooking in many cases. Keep in mind that saturated fats such as coconut oil are the best choice for high heating, as is the case with deep frying, as they are the least prone to oxidation.

Olive oil: Olive oil is rich in anti-inflammatory compounds including polyphenol antioxidants that can prevent heart disease and mental decline (38).
Coconut oil: Coconut oil is one of the best oils for cooking at high temperatures and it may help increase levels of good cholesterol (39).
Avocado oil: Avocado oil is heat resistant and contains carotenoid and polyphenol antioxidants, which may have beneficial effects on heart health (40).

The following oils should be reserved for dressings and other applications that do not involve heat:

Flaxseed oil: studies show that flaxseed oil may help lower blood pressure and reduce inflammation (41).
Walnut oil: Walnut oil has a rich, nutty flavor and has been shown to lower high blood sugar levels and high cholesterol (42, 43).
Hemp seed oil: Hemp seed oil is highly nutritious and has a nutty flavor that goes perfectly with salad dressings (44).

Conclusion

Rapeseed oil is a seed oil that is often used in cooking and is also widely used in food production.

There are many contradictory and inconsistent research results on canola oil. While some studies link canola oil to better health, many studies suggest that canola oil causes inflammation and can damage memory and the heart.

Until better quality long-term studies are available, it may be better to choose oils such as extra virgin olive oil that are proven to be healthy.

References

https://www.healthline.com/nutrition/is-canola-oil-healthy#bottom-line