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Canola Oil Debate

While fats were once blacklisted, we now recognize the benefits of consuming healthy fats as part of a balanced diet. However, there remains some debate over which fats deserve the designation of “healthy.” There’s a general agreement about some fats belonging to the healthy category, such as olive oil and fish oil, and others to the unhealthy side, such as trans fat.

Some other fats are still hotly debated, with one side promoting their health benefits and the other side arguing the opposite. Canola oil falls into this category, making it difficult to decide if it deserves a place in your pantry.

The 411 on Canola Oil

Canola oil is engineered from rapeseed to have lower levels of erucic acid (less than 2 percent compared to more than 40 percent in original rapeseed) and glucosinolates (under 30 umol/gram). Rapeseed is a crop in the Brassica family, related to mustard, cabbage, and broccoli, and contains more than 40 percent oil. Since its debut in the 1970s, canola oil has become a popular choice for oils and is the third largest vegetable oil, coming in behind palm oil and soybean oil.

Based on one study, the fatty acid makeup includes:

  • Oleic acid (a non-essential fat): 56.80 – 64.92%
  • Linoleic acid (an essential fat): 17.11 – 20.92%
  • Palmitic acid (a non-essential fat): 4.18 – 5.01%

Another study measured 62.5% oleic acid, 19.6% linoleic acid, 10% alpha-linolenic acid (ALA), and 4.3% palmitic acid, with some small amounts of other fatty acids. Additionally, canola oil contains some phytonutrients, including tocopherols, which have some health-promoting properties.

Comparison of dietary fats

Dietary fatty acid ratios. Source: https://commons.wikimedia.org/wiki/File:Comparison_of_dietary_fats.gif

Some of the health promotion of canola oil comes from its high percentage of oleic acid and balance of omega-6 and omega-3 oils, including a fair amount of ALA, all of which have been correlated with a reduced risk of many chronic illnesses. Unrefined canola oil also contains antioxidants including phytosterols, vitamin E, and coenzyme Q.

Does this information translate to putting canola oil in your rotation of fats in your diet? Let’s see what the literature has to say about the benefits and the disadvantages of this dietary oil.

Benefits of Canola Oil

Over the years, there have been several studies demonstrating the health benefits of canola oil, especially in terms of cardiovascular health:

  • A small study from the 1990s substituted saturated fats with mono- or polyunsaturated fats, comparing canola oil, corn oil, and olive oil. The cholesterol levels lowered on all three of the diets, with a 16%, 17%, and 13% reduction of LDL cholesterol for canola, corn, and olive oil respectively. Another study found that canola oil and soybean oil led to better fatty acid profiles and cholesterol markers than palm and partially hydrogenated soybean oils.
  • In a recent single-blind, randomized control trial on women with type-2 diabetes, canola oil and rice brain oil led to improvement in blood lipids compared to sunflower oil.
  • In one randomized controlled trial on those with type-2 diabetes, a canola oil-enriched diet combined with a low-glycemic diet led to improved glycemic control, especially in those who had higher systolic blood pressure. There was also a significant reduction in total cholesterol, triglycerides, and HDL-C in the test diet compared to the control diet.
  • In one study in men with nonalcoholic fatty liver disease, canola oil and olive oil led to improvements in markers for the liver disease as well as insulin resistance compared to the control group consuming soybean and sunflower oils. Olive oil performed better than canola oil.
  • In a randomized, controlled cross-over trial, 15 subjects consumed a dairy-rich diet or a diet rich in rapeseed oil. The canola diet led to lower serum total cholesterol, LDL cholesterol, triglycerides, and the ratio of total to HDL cholesterol compared to the dairy diet.
  • Compared to soybean oil, canola oil promotes better bone health. One mouse study found that consuming the canola oil correlated to maintenance of the LV4 and femur parameters, while soybean was unfavorable to most bone parameters.

One thing to note about most of these studies supporting health benefits of canola oil is that they generally test canola oil against other vegetable oils, some of which have been associated with chronic disease, and some studies were performed on animals rather than humans.

Arguments Against Using Canola Oil

Two main arguments that the anti-canola oil camp uses are its erucic acid content and its processing. Most modern canola oils have low levels of erucic acid, making this argument moot.

In terms of processing, most conventional oils go through many stages, including high heat, deodorizing, exposure to solvents, and more, which impacts the composition of the final oil:

  • Processing, especially the heat, has the potential to turn heart healthy fats (especially ALA) into trans fat. In one study, standard refined rapeseed oil had a total trans fat content of 1.15, compared to 0.33 in cold-pressed rapeseed oil. Cold-pressed also had higher levels of additional health-benefiting components, such as phospholipids, polyphenols, tocopherols, and phytosterols.
  • Many who do not like the use of canola oil are concerned about the hexane residue, which is one of the solvents used during processing. In one study, rapeseed oil had between 0.010 mg/kg and 0.233 mg/kg amounts of n-hexane, while virgin rapeseed oil had none detected. Additionally, some of the rapeseed oil samples also had trace levels of acetone, benzene, and toluene.

Another concern surrounding canola oil is that it is often genetically modified. The safety of GMOs is largely debated. One review study found that most studies on the safety of GMOs only last for a period of 90 days or less, and they found potential for weight gain as well as liver and kidney issues in those consuming GMOs. Although assurances of the safety of GMOs continue, the lack of lengthy assessment leaves a lot of questions as to their potential long-term impact on human health.

Concerns about canola oil may not just be related to the processing; recently, there have also been studies demonstrating negative impacts of consuming canola oil:

  • A recent mouse study looked to see the impact of canola oil on markers of Alzheimer’s disease. Those who consumed the canola oil had a significant deficit in working memory and a decrease in the immunoreactivity of a synaptic protein, PSD95. There was also a negative impact to the amyloid beta 42/40 ratios, as well as a significant increase in body weight. Conversely, the same researchers tested olive oil and found a beneficial and protective effect.
  • In one recent rat study comparing canola oil with pure palm olein oil and hydrogenated palm oil, all three groups experienced an increase in total cholesterol, triglycerides, and HDL cholesterol. Although, the olein oil and canola oil groups did have a reduction in LDL, all three groups, including the canola oil group, experienced an increase in oxidative LDL and MDA levels and a reduction in PON1 activity compared to the control group, all of which increases the risk of atherosclerosis.
  • One study found that consuming canola oil led to a reduced antioxidant status and a higher level of plasma lipids, which led to increased oxidative stress in stroke-prone spontaneously hypertensive rats. There was also a significant increase in blood pressure, even without the addition of salt. This effect led to a shortened lifespan in the rats compared to those consuming soybean oil diets.

Some of these studies have the same limitations mentioned above: comparing the oils with other vegetable oils and using animal models rather than human studies. Additionally, most studies with canola oil or rapeseed oil are mainly limited to outcomes based on biomarkers, rather than examining the relationship of the oil with disease incidence, as in many studies of olive oil.

Some of the concerns regarding the oil may only relate to standard processed oils rather than organic, cold-pressed options. However, as with all oils, it’s important to note that cooking and heat will lead to changes in structure and constituents. So while organic, cold-pressed canola oil may have health-promoting compounds, most uses of canola oil include high-heat cooking.

Canola oil, having a relatively low ratio of antioxidants to PUFA, may lead to significant losses of antioxidants and increase lipid peroxidation, depending on temperature and time. One study found that vitamin E was significantly depleted using conditions designed to replicate use for deep frying, and another study found that production of a toxic volatile compound called acrolein by canola oil at 180°C was found to be around five times higher than acrolein production by either extra virgin olive oil or olive oil, most probably due to the high ALA content of canola oil and fewer antioxidants than olive oil.

As you can see, there is no easy answer to the debate about canola oil. It is not the healthiest oil, as some studies have pointed to enhanced benefits with olive oil.

If you would like my personal take—I do not use canola oil at home. However, I don’t strictly avoid it in healthy food products if it is organic. My basic premise for dietary oils is the following:

  • Don’t cook with oils; cook with water.
  • Keep them out of heat, light, and reduce exposure to oxygen.
  • Use a variety of oils. Some of the ones I use are avocado oil, rice bran oil, extra-virgin olive oil, coconut oil, flaxseed oil, and butter, to name a few. I will buy different brands of these different oils.

So, should you stay away from canola oil? That is up to you, as well as your doctor or nutrition professional. Hopefully, this snapshot into the literature provides a place to begin making your own decision.

 

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