#1 Are canola and rapeseed identical? Why is it necessary that it’s genetically modified?

No, they’re not identical. High concentrations of erucic acid (EA) can be found in original rape lines (therefore called HEAR — high erucic acid rapeseed). When negative health effects of this fatty acid became known, scientists started developing plants with lower concentrations of EA. Since the 1950s this has been achieved by cultivation. Integrating a certain feature into a plant line through cultivation takes time, therefore the process is nowadays facilitated by genetic modification.

The line produced was called canola and is now almost exclusively cultivated in the U.S. and Canada. The EA content has been reduced from approximately 50% to under 0.5% and is now unproblematic for humans to consume.

#2 What is erucic acid and how can it affect your health?

Erucic acid is an unsaturated omega-9 fatty acid. Its metabolism works like for other fatty acids, but the breakdown for energy production in the cells is disturbed in the heart. Instead, it is stored there — and thus the heart muscle becomes fatty (lipidosis), which impairs its function and can lead to heart attacks. This mechanism was especially observed in the young. The consumption of erucic acid should therefore be avoided.

However, the liver is able to excrete EA and can completely reverse the harmful effects. Permanent damage to the heart can thus be avoided as soon as consumption is reduced.

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#3 What are safety limits for erucic acid and what products should you avoid?

Due to the health hazard, the first maximum levels were introduced for baby food as early as 1995. In 2003, no observed effect levels (NOAEL) were set, after conducting some animal experiments. Those are used to calculate tolerable daily intakes (TDI) for humans (multiplied with factor 10 for comparing animals to humans and again factor 10 for variation between humans). Those experiments were updated in 2016 by the EFSA and a final TDI of 7.0 mg EA/kg body weight per day was set.

High levels are found mainly in rapeseed oils (1.3–5.2 mg/kg), pastries (240–290 mg/kg) and biscuits (220–290 mg/kg). Those levels are especially problematic for babies and infants, due to their lower body weight and their immature liver, which can’t facilitate the excretion of EA like adults.

An example calculation shows that, although the risk for children is higher, with moderate consumption any harm can be avoided!

#4 Canola oil is high in unsaturated fats (especially omega-6), what does that mean for your health?

Canola consists of 90% unsaturated and 10% saturated fats. Contrary to popular belief that saturated fats have particular health benefits (which hasn’t been scientifically proven yet), MUFAs and PUFAs do have scientifically proven positive health effects.

An unbalanced ratio of omega-6 to omega-3, can be disadvantageous— it should tend towards 1:1, but is unbalanced in most foods. This is not the case with canola (20% omega-6 to 10% omega-3).

However, the type of omega-6 fatty acid must also be differentiated here. A study showed that the positive effects of PUFAs don’t apply for all of them — for example, the single substitution with linoleic acid (18:2 omega-6) didn’t have such a positive influence. Substituting a mixture of omega-6/omega-3 did. Canolas PUFA is mainly linoleic acid.

However, a more credible large-scale meta-analysis showed that canola oil — in contrast to saturated fats — promoted the reduction of cholesterol and LDL due to its high content of MUFAs and PUFAs.

The story about saturated and unsaturated fats is not yet finished.

#5 People say canola is unhealthy, because it’s a refined oil. What effects does the refining have, compared to cold-pressing?

Refining oil removes impurities, contaminants, free fatty acids (which can oxidize), pesticides, unwanted pigments, and flavors. Most controversial are the processes of extraction with chemicals like hexane and bleaching, as well as the formation of trans-fatty acids.

  1. Extraction with hexane avoids unnecessary heating (and thus the formation of trans-fatty acids). The solvent hexane is completely evaporated after extraction and doesn’t remain in the crude oil. Further chemical treatments serve only the improvement of safety — for example, low-concentrated organic acid precipitate harmful metals.
  2. Afterward, bleaching can be performed with bleaching earth or bleaching clay — both are used in quantities <1% and are harmless to humans. It’s not a chlorine bleach as used for cleaning the toilet. It removes unwanted dyes and also pesticide residues.
  3. Deodorization removes undesirable flavors by heating — this step is responsible for the formation of trans-fatty acids and is therefore disadvantageous. In total <1% trans-fatty acids are formed.

Contrary to some popular beliefs, essential fatty acids are not fully destroyed by refining and the fatty acid structure is mostly preserved. Cold-pressed oil doesn’t go through this whole process and is, therefore, more nutritious and natural. There is no formation of trans-fatty acids. However, flavors, colorings, and possible contaminations remain, which can reduce the overall quality. From a nutritional point of view, cold-pressed is nevertheless preferable.

#6 Canola oil is reputed to be unstable and in need of synthetic antioxidants — is it?

Chemical instability is caused by unsaturated double bonds. These fatty acids have a different structure than saturated ones — and are more susceptible to external attacks, such as heat or oxygen from the air. When they fall apart, oxidation products can be formed, which are disadvantageous for health and taste.

Antioxidants that occur naturally in oils (e.g. vitamin E/tocopherol) can counteract this. When comparing production methods of oils — natural cold-pressed, virgin or hot-pressed and refined crude, bleached and deodorized — the refined crude oil (before bleaching and deodorizing) shows the highest contents of natural antioxidants. It also shows the highest oxidative stability in the Rancimat test. This is due to the fact that refining removes oxidizing substances. Refined canola oil, despite the high content of unsaturated fatty acids, is more stable than the cold-pressed version.

The most unstable oil is indeed the highly praised cold-pressed oil, which is completely natural, because untreated, and in its natural form has many unsaturated bonds that can still be oxidized. Therefore, a particularly careful storage is absolutely necessary (in the fridge). However, it is not only stability that is decisive for nutritional values — this is where cold-pressed oil triumphs over refined oil.

#7 When applying heat to oils during refining, trans-fatty acids can be formed — the same goes for frying then, right?

Yes. Trans-fatty acids are mainly produced by heat, in the refining step deodorization, as well as during deep-frying at home. Unsaturated fats are not suitable for deep-frying. However, the most heat-stable fats are simultaneously the most disadvantageous — the saturated fats. They have no free double bonds and are extremely robust. So you have the choice between trans-fatty acids derived from unsaturated fatty acids or the cardiovascular disadvantages of saturated fatty acids. Don’t fry!

For further reading

Ask the Expert: Concerns about canola oil (from Havard School of Public Health)

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