The journey from the field to a bottle of cooking oil is a long one.
Yellow rapeseed flowers blooming in a field in Østre Gausdal, Eastern Norway. Much of Norway's rapeseed is used for animal feed, but some is made into cold-pressed oil.(Photo: Javad Parsa / NTB)
Concerns and scepticism about vegetable oils are becoming increasingly common on social media.
One person writes: 'Vegetable oils/margarines are poisonous and harmful to your health – they are ultra-processed, chemically manufactured products with hardly any real raw ingredients!'
Another writes: 'Try looking up how they're made...' A third asks: 'Is any of this actually produced in Norway?'
We asked Gjermund Vogt at Eurofins how vegetable oils are made.
Eurofins laboratories analyse foods and oils on behalf of researchers and the food industry. Vogt himself has researched fats and oils for 30 years and has contributed to more than 50 scientific publications.
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From field to factory
The only oil made from Norwegian raw materials is cold-pressed rapeseed oil. Other vegetable oils from sunflower, corn, soybean, and olive are either produced in Norway using imported raw materials or imported as finished oils. The process of producing oil from plants is more or less the same regardless, according to Vogt.
Rapeseed, however, is grown in Norwegian fields. The plants are harvested in the usual way, with the combine harvester separating the seeds from the rest of the plant.
The seeds are then cleaned to remove weeds, small stones, and insects before being dried.
"If the seeds are too moist, they start to sprout and go mouldy. Drying makes it possible to store them," Vogt explains.
The oil is pressed out
At the factory, the seeds are fed into a screw press, which mechanically squeezes out the oil. Some plant material still remains in the oil, so it is filtered or centrifuged.
The result is a cold-pressed oil that can be shipped to stores.
But there is still oil left in the seeds and plant material.
"Cold pressing only extracts about 60–65 per cent of the oil in the seed," says Vogt.
Olives are hand-picked or harvested with machines that shake the tree and collect the fruit in large nets. Here, the harvest is monitored at an olive oil mill in Athens, Greece.(Photo: Thanassis Stavrakis / NTB)
A solvent extracts more oil
To get out the rest, the leftover plant material is processed further. A solvent called hexane is used to extract the remaining oil. This particular solvent has been the subject of much speculation.
"Extracting oil with hexane is used to a limited extent for rapeseed, but more extensively for soybeans, whose seeds contain so little fat that mechanical pressing alone cannot get it out," says Vogt.
Hexane is a petroleum-derived solvent. It is flammable and toxic if you are exposed to large amounts. The solvent is evaporated from the oil and reused.
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"There are no traces of hexane left in the finished oil. It costs much more than the oil itself, so the hexane is recovered," says Vogt.
Olive oil goes through several stages of processing before it reaches store shelves. Here, at a facility in Quesada, Spain.(Photo: Bernat Armangue / AP / NTB)
The oil is washed
The oil is then refined. This process is also frequently criticised on social media by people who are sceptical of vegetable oils.
The purpose of refining is to remove impurities and unwanted odours, according to Vogt. Refining also makes the oil less prone to going rancid than cold-pressed oil, allowing it to be stored for longer.
The first step is washing the oil with water, followed by a dilute lye solution.
"Clean water removes unwanted water-soluble substances. The lye removes free fatty acids," Vogt explains. "The lye is then rinsed out with water, much like the lye is washed out of lutefisk."
Lutefisk is a traditional Norwegian dish made from dried cod that has been soaked in a lye solution. It has a gelatinous texture.
Gjermund Vogt has worked with oils for three decades. He recently presented his work at a fat seminar at the Norwegian food research institute Nofima.(Photo: Eurofins)
The oil is bleached
The next stage is known as bleaching. Sand and shells from algae, or sometimes activated carbon, are used.
"These are natural substances, and they are used to remove colour pigments that can cause the oil to become rancid more quickly," says Vogt.
Algae shells are also used to filter juice, wine, and beer.
"Some people think chlorine is used during purification, but that's not true. The industry does not use chemicals to bleach oil," says Vogt.
The final stage is steam distillation. This process lowers the boiling point of liquids by removing air, allowing different substances to be separated without being damaged.
“The goal is to remove any remaining unwanted substances, including possible pesticides and environmental contaminants from the field,” says Vogt.
Finally, antioxidants such as vitamin E and, in some cases, rosemary extract are added to the oil.
Finally, the olive oil is transferred into storage tanks or bottles. This facility is located outside Athens in Greece.(Photo: Thanassis Stavrakis / NTB)
Is the oil ultra-processed?
Does this refining process make vegetable oils ultra-processed?
The term ultra-processed was introduced by Brazilian nutrition researcher Carlos Monteiro. He developed the now well-known NOVA food classification system. Vegetable oils are not regarded as ultra-processed under this definition, but as processed raw materials, also called processed ingredients.
The NOVA system categorises foods based on why they are processed and what is added during processing – not on the number of processing steps involved.
Despite undergoing several treatments, refined oil consists almost entirely of pure fat. Aside from vitamin E and, in some cases, rosemary extract, no additives are introduced.
What about trans fats?
Another claim often seen on social media is that vegetable oils contain trans fats.
Trans fats occur naturally in cows and sheep and are therefore found in small amounts in milk and meat. This type is not considered harmful.
Industrial trans fats, also called hydrogenated fats, are made by adding hydrogen to vegetable oils to make them firmer and more shelf-stable. They were widely used until the 1990s, particularly in biscuits, cakes, french fries, and fast food. Research later showed that hydrogenated fats increased the risk of heart disease, inflammation, and type 2 diabetes.
In Norway and the EU, industrial trans fats are strictly regulated, with a maximum limit of two grams per 100 grams of fat in food products. According to Vogt, they have now been largely eliminated from Norwegian and European foods.
On social media, you can find claims such as: 'You should avoid vegetable oils because they contain too much omega-6 content (which promotes inflammation, etc.).'
Omega-6 is just as essential as omega-3 for the body to function well. Both play important roles in regulating inflammation, the immune system, and blood pressure. There is no need to take omega-6 supplements, but there is also no point in reducing your intake, according to the Norwegian Directorate of Health (link in Norwegian).
"It's true that vegetable oils contain the most omega-6, but that's not a problem in a normal diet. Human studies show no evidence that vegetable oils promote inflammation," says Vogt.
He adds that rapeseed oil is considered particularly beneficial because it has an omega-6 to omega-3 ratio of roughly two to one.
However, Norwegian health authorities do not recommend any specific ratio between omega-3 and omega-6. There is no scientific basis for defining one, according to the Norwegian Directorate of Health (link in Norwegian).
Seek reliable knowledge
Rapeseed oil may have gained a bad reputation because older varieties of rapeseed once contained erucic acid, a fatty acid linked to heart disease in men, as well as substances that affected growth in calves.
"Both of these were naturally bred out of rapeseed in the 1950s. Rapeseed oil on the market today no longer contains these harmful substances, but old stories tend to persist," says Vogt.
He encourages people to learn about vegetable oils through scientific journals rather than social media.
"Many present themselves as health experts without really understanding what they're talking about. They use technical terms from the oil refining process, such as extraction and distillation, and make them sound dangerous. If you're unfamiliar with the process, it's easy to believe something frightening is going on," says Vogt.
