Canola oil has long been a staple in households as it is cheap, convenient and labelled “heart healthy” given that it contains no cholesterol. However more and more we are being told to steer clear of canola as it is potentially one of the worst oils for our health. What gives?
What is canola oil?
Canola oil comes from rapeseed, but has the erucic fatty acid stripped from it (this is toxic and has a bitter flavour). Canola contains good amounts of long chain polyunsaturated fats (PUFA) and essential fatty acids that we can’t produce in the body and must be supplied by the diet.
This includes linoleic acid, an omega 6 fatty acid, and alpha-linolenic acid (a plant source of omega 3 fatty acid), earning canola its “heart healthy” label.
The problem is, the chemical structure of PUFA in this form (many carbon atoms without hydrogen atoms, to be a geek about it) leaves them more vulnerable to being broken down or oxidised if they turn rancid before consuming (left too long, or exposed to sunlight), or heated to a high temperature.
This results in a chemical structure change that is pro-inflammatory. Notwithstanding that, plant-based omega 3 fats have a very low conversion rate to the longer chained forms known to reduce inflammation.
The way canola is produced removes or destroys most of the health properties these essential fats would naturally offer. Seed oils are produced either by rendering the oil out of the seed (using a heat method, though this isn’t common); by using a solvent (such as hexane) then evaporating off the solvent using heat; or via a mechanical method, pressing it out (this is labelled as “cold pressed”). The next step is to refine them further, often removing most of the nutrients from them.
Most canola oil varieties on the shelves are stored in light bottles. This leaves them exposed to sunlight and at greater risk of becoming oxidised. Why does this matter?
The fats we eat are stored in the cell membranes and adipose tissue — once consumed, those that are easily oxidised leave us much more exposed to inflammation, particularly in combination with an environment that is already stressful on the body (such as too little recovery from exercise or not enough exercise), a nutrient-poor diet, excessive alcohol consumption, chronic stress or alcohol intake).
This is where processed foods come in
When we layer this type of cooking oil on top of our Western food supply, things can look pretty grim for the unsuspecting consumer. Omega 6 fats work best when they are in balance with omega 3 fats, the latter found predominantly in fatty fish such as salmon, mackerel and sardines or in plant sources such as flaxseeds and chia seeds.
They are universally recognised as important for heart health, and for protecting against conditions of inflammation (such as arthritis, gut permeability, migraines and high circulating blood sugar to name just a few). Omega 6s are also important for inflammation, helping with reducing menstrual symptoms and nerve inflammation.
However when we have too much of these, the conversion of plant sources of omega 3s can be blocked, further upsetting the balance of longer chained fats. The proliferation of processed foods that use canola oil (as a cheap oil) creates an imbalance in the PUFA present in the body that are necessary for protecting us against inflammation.
Consuming foods rich in omega 6 fats naturally (such as nuts, seeds, avocados) isn’t a problem for most people —the problem could be the excessive consumption of added fat with high omega 6 content. Therefore, the less we use oils high in omega 6 fats as cooking oils or salad dressing oils the better.
Given this information, do we take or leave canola?
My recommendation is to leave it and choose another oil to cook or use in salad dressing. Coconut, olive or avocado oil are all examples of more stable cooking oils to choose. These oils have a better fatty acid profile and antioxidants that are naturally present which help protect them during the cooking process.
Look for an oil sold in a dark-coloured bottle and store it away from the heat in a dark place, to minimise the likelihood of oxidation.
If you are after a neutral oil for salad dressing, then there is now a high-oleic rapeseed oil available — a less processed form of canola oil. This process neutralises some of the issues I’ve described earlier by reducing the PUFA content and increasing the amount of oleic acid, which is less prone to oxidation.