A recent study published by two Italian researchers in Scientific Reports[1], showed that a diet enriched with canola oil can produce a deficit of working memory and synaptic pathology.
In a transgenic mice model.
Dementia is an immensely burdensome disease. To prevent this condition simply by stopping the use of canola oil seems too easy to be true. Indeed, the above researchers pointed out that no significant effect on β-amyloid deposits were shown and that the mice, which consumed a chow enriched with canola oil, also increased their weight. Oils are made of fat and there is evidence that a high-fat diet can indeed disrupt memory[2]. This makes it difficult to tell whether the effects observed on the mice’s memory were due to the high-fat diet or to the weight gain.
Considering the effects of a high-fat diet on memory, it would have been interesting to see a comparison with olive oil, which is considered one of the healthiest oils. Unfortunately, this comparison has not been done. Animal models are not new to generate results that are not confirmed in humans, especially in experiments where oils are tested. Elevated oleic acid consumption alters hepatic lipid metabolism and promotes atherosclerosis by enriching LDL particles with cholesteryl oleate[3]. This result, obtained in animals, was not confirmed in human studies such as the PREDIMED intervention trial[4].
Should we conclude that canola oil consumption increases the risk for dementia based on the above? I think it is too early to say that. But, what is canola oil and is it healthy?
Let’s start with a bit of history: canola oil comes from rapeseed, also known as colza, a very common plant in North Europe. This plant belongs to the Brassica botanical family that also includes cauliflowers and cabbages. Colza/Rapeseed oil was a central topic in a movie starring Nick Nolte and Susan Sarandon called “Lorenzo’s oil[5],” in which the two American actors played the role of an Italian couple who discovered that erucic acid-rich oils (such as rapeseed oil) could be effective in slowing down the progression of X-linked Adrenoleukodystrophy, their son was suffering from.
Rapeseed oil has traditionally been used for non-food purposes. It was a typical illuminant in oil lamps and it is still used by the fuel industry [6]. In more recent times rapeseed oil has been used extensively – particularly in Europe – for biodiesel. However, back in the 70’s, farmers in Canada were able to select, through traditional plant cross-breeding, a new variety of the rapeseed plant, which contained less of both erucic acid (which is toxic at high doses) and the goitrogens compounds glucosinolates. This newly-developed breed was named “Canola”, a combination of “Canadian” and “Oil” (or “Ola”), and contains less than 2% erucic acid and less than 30 micromoles of glucosinolates. A third generation was developed by reducing significantly the polyunsaturated acid content. These oils, known as mid- and high-oleic acid canola oils, are also suitable for industrial frying, constituting a trans-fat replacement option for the food industry[7].
As a result of all these improvements, canola oil is now usually considered a healthy product, low in saturated fats, high in oleic acid (50-60% of fatty acids), and with a good omega-6/ omega-3 ratio. It is now available in Europe as virgin rapeseed oil obtained by pressing rather than by solvent extraction and characterized by a better taste and greater acceptance by consumers[8]. Canada is currently one of the major exporters of both seeds and seed oils[9] and produces 3 million tons of canola oil per year, a great deal of which is exported to the US[10]. Canola contributes 26.7 billion USD to the Canadian economy each year, generating over 250,000 jobs and 11.2 billion USD of wages (Source: Canola Council of Canada).
Thanks to the high content of monounsaturated fatty acids, canola oil is considered by many a valid but cheaper replacement for olive oil, the undiscussed king of the Mediterranean diet. As a result, canola oil consumption has significantly increased in non-Mediterranean countries[11] [12].
Despite conflicting experimental animal studies[13] [14], Canola oil was shown already years ago to be able to reduce total and LDL cholesterol, with conflicting results about the effects on HDL-C[15] [16] [17].
A diet enriched with canola oil and low in glycemic load can improve glycemic control in patients with type 2 diabetes, especially those with high systolic blood pressure[18]. It was also shown that consuming rapeseed oil for 4 weeks can improve serum lipids, liver enzymes, and basal inflammation in the adipose tissue more than olive oil. However, consumption of a meal with these oils induced an acute pro-inflammatory response in the adipose tissue[19]. In a randomized, single-blind, controlled trial study performed in Iran among women with type 2 diabetes[20], rice bran oil and canola oil were both found to improve blood lipids better than sunflower oil.
Also, the currently running Canola Oil Multicenter Intervention Trial (COMIT), showed that consumption of CanolaDHA, a novel DHA-rich canola oil, improves HDL cholesterol, triglycerides, and blood pressure, thereby reducing Framingham Risk Score compared to other oils (unfortunately not including olive oil)[21] varying in unsaturated fatty acid composition[22].
Finally, a recent trial[23] provided further clinical evidence that diets rich in oleic acid (also present in olive oil) from canola oil have benefits for cardiovascular health.
Canola oil is a healthy and less expensive alternative to olive oil. The choice between one oil and the other is a matter of taste, price and, of course, latitude!
[1] Lauretti and Praticò (2017). Effect of canola oil consumption on memory, synapse and neuropathology in the triple transgenic mouse model of Alzheimer’s disease. Scientific Reports 7, Article number: 17134. https://www.nature.com/articles/s41598-017-17373-3.
[2] Sobesky et al. (2014). High-fat diet consumption disrupts memory and primes elevations in hippocampal IL-1β, an effect that can be prevented with dietary reversal or IL-1 receptor antagonism. Brain Behav Immun. 2014 Nov;42:22-32.
[3] Degirolamo C, Shelness GS, Rudel LL. LDL cholesteryl oleate as a predictor for atherosclerosis: evidence from human and animal studies on dietary fat. Journal of Lipid Research. 2009; 50:S434–S439.
[4] Zampelas A. Nuts and not olive oil decrease small and dense LDL: results from the PREDIMED Study. Atherosclerosis. 2013 Nov;231(1):59-60.
[5] Lorenzo’s oil: https://en.wikipedia.org/wiki/Lorenzo%27s_Oil.
[6] Dworakowska et al. (2011). Production of biodiesel from rapeseed oil. World Sustainability Forum. file:///Users/gianluca/Downloads/wsf_631_original.pdf.
[7] List GR (2017). Rapeseed (canola) oil. Lipid Technol. Vol. 29, No. 5-6.
[8] Matthaus B, Brühl L, Amoneit F. The DGF Rapeseed Oil Award – A tool to improve the quality of virgin edible rapeseed oil. Lipid Technol 2008; 20:31–4.
[9] Gunstone FD (2012). Rapeseed (canola) oil. Lipid Technol. Vol. 24, No. 2. http://onlinelibrary.wiley.com/doi/10.1002/lite.201200173/full.
[10] Canola Council of Canada: https://www.canolacouncil.org/markets-stats/industry-overview/.
[11] Lin, L. et al. Evidence of health bene ts of canola oil. Nutrition Review. 71, 370–385 (2013).
[12] Dupont, J. et al. Food safety and health e ects of canola oil. J Am Coll Nutr. 8, 360–375 (1989).
[13] Cai, J. et al. Comparative Efeects of Plant Oils on the Cerebral Hemorrhage in Stroke-Prone Spontaneously Hypertensive Rats. Nutr Neurosci. 19(7), 318–326 (2014).
[14] Junker, R. et al. Effects of diets containing olive oil, sunflower oil, or rapeseed oil on the hemostatic system. Thromb Haemost. 85(2),280–6 (2001).
[15] Gustafsson IB, Vessby B, Ohrvall M, Nydahl M. A diet rich in monounsaturated rapeseed oil reduces the lipoprotein cholesterol concentration and increases the relative content of n-3 fatty acids in serum in hyperlipidemic subjects. Am J Clin Nutr. 1994 Mar;59(3):667-74.
[16] McDonald B, Gerrard J, Bruce V, et al. Comparison of the effect of canola oil and sunflower oil on plasma lipids and lipoproteins and on in vivo thromboxane A2 and prostacyclin production in healthy young men. Am J Clin Nutr. 1989;50:1382–1388.
[17] Lichtenstein AH, Ausman LM, Carrasco W, et al. Effects of canola, corn, and olive oils on fasting and postprandial plasma lipoproteins in humans as part of a national cholesterol education program step 2 diet. Arterioscler Thromb. 1993;13:1533–1542.
[18] Jenkins et al. (2014). Effect of lowering the glycemic load with canola oil on glycemic control and cardiovascular risk factors: a randomized controlled trial. Diabetes Care. 2014 Jul;37(7):1806-14. https://www.ncbi.nlm.nih.gov/pubmed/24929428.
[19] Kruse et al. (2015). Dietary rapeseed/canola-oil supplementation reduces serum lipids and liver enzymes and alters postprandial inflammatory responses in adipose tissue compared to olive-oil supplementation in obese men. Mol Nutr Food Res. 2015 Mar;59(3):507-19. https://www.ncbi.nlm.nih.gov/pubmed/25403327.
[20] Salar A, Faghih S, Pishdad GR. Rice bran oil and canola oil improve blood lipids compared to sunflower oil in women with type 2 diabetes: A randomized, single-blind, controlled trial. J Clin Lipidol. 2016 Mar-Apr;10(2):299-305. https://www.ncbi.nlm.nih.gov/pubmed/27055960.
[21] The other oils were: 1) conventional canola oil (Canola; n-9 rich), 2) a blend of corn and safflower oil (25:75) (CornSaff; n-6 rich), 3) a blend of flax and safflower oils (60:40) (FlaxSaff; n-6 and short-chain n-3 rich), or 4) high-oleic acid canola oil (CanolaOleic; highest in n-9).
[22] Jones et al. (2014). DHA-enriched high-oleic acid canola oil improves lipid profile and lowers predicted cardiovascular disease risk in the canola oil multicenter randomized controlled trial. Am J Clin Nutr. 2014 Jul;100(1):88-97.
[23] Jones PJH (2015). High-oleic canola oil consumption enriches LDL particle cholesteryl oleate content and reduces LDL proteoglycan binding in humans. Atherosclerosis. 238(2): 231–238.
