All oils are composed, in varying proportions, of three types of fatty acids: saturated , monounsaturated and polyunsaturated . They are classified according to the predominant fatty acids. Olive and canola (or rapeseed) oils, increasingly popular in North America, are largely made up of monounsaturated fats. These are known to exert several beneficial effects on health. Other active compounds present in these oils can bring health benefits.

Active ingredients and properties

Olive and canola oils are made up of more than 85% of unsaturated fatty acids (monounsaturated and polyunsaturated). Unsaturated fats have positive effects on blood lipids (e.g. cholesterol levels) when they replace saturated and trans fats in the diet ^{1 , 2} . They reduce the risk of coronary heart disease ³ .

In the United States, the label on bottles of olive oil and canola and on certain products that contain them may highlight the beneficial effects of monounsaturated fats against coronary heart disease. The Food and Drug Administration (FDA), the US agency responsible for food control, has authorized such health claims ^{4 , 5} . In Canada, these claims are not allowed.

Olive oil

Olive oil occupies an important place in the traditional diet of Mediterranean countries (Greece, Italy, South of France, Tunisia, Morocco …). This is their main source of fat ⁶ . Studies have reported a reduction in the risk of myocardial infarction ⁷ , mortality from coronary heart disease and total mortality ⁸ in people consuming a Mediterranean diet , including the consumption of olive oil.

The precise impact of olive oil on the risk of coronary heart disease remains controversial. Indeed, its consumption has sometimes been associated ⁹ , other times not ^{10 , 11} , with a reduction in the risk of myocardial infarction in different cohorts.

In addition, the consumption of olive oil is linked to the improvement of various risk factors for cardiovascular disease ¹²  : better control of blood pressure ¹³ , decrease in blood levels of triglycerides , glucose ¹⁴ , total cholesterol and of LDL cholesterol ( “bad”) cholesterol ^15,16 and an effective anticoagulant ¹⁷ .

Some studies indicate a link between the intake of olive oil (or monounsaturated fatty acids from, among other things, olive oil) and the prevention of breast cancer ^18-22 and colon ²³ .

Monounsaturated fatty acids . Olive oil contains a particularly high amount of monounsaturated fat, which represents 80% of its lipid content. A diet rich in monounsaturated fats is linked to a reduced risk of cardiovascular disease ²⁴ . These fats have the potential to lower the levels of total cholesterol and LDL cholesterol ( “bad”) cholesterol in the blood, when they replace saturated fats in the diet ¹ . Furthermore, they could also increase the levels of HDL-cholesterol ( “good”) cholesterol when they replace some carbohydrate food ²⁵. Also, monounsaturated fats protect against the oxidation ²⁶ of LDL cholesterol , thus helping to prevent the atherosclerosis .

Almost all of the monounsaturated fatty acids in olive oil are made up of oleic acid . Even if North Americans consume much less olive oil than people in Mediterranean countries, their intake of oleic acid would still be similar to that of these populations ²⁷ . In the North American diet, this fatty acid comes mainly from meat and poultry (such as pork and chicken), rather than from olive oil ²⁸ .

Antioxidants . Antioxidants are compounds that protect the cells of the body from damage caused by free radicals. These are very reactive molecules which are implicated in the development of cardiovascular diseases , certain cancers and other diseases linked to aging ²⁹ . All vegetable oils naturally contain antioxidants, in greater or lesser quantities. This is what protects them against oxidation ³⁰ . In general, the more unsaturated an oil, the more it is rich in antioxidants.

• Phenolic compounds . Olive oil (virgin or extra virgin) contains a significant amount of phenolic compounds, the main ones being hydroxytyrosol and oleuropein ³¹ . It has been well demonstrated that the phenolic compounds in olive oil have antioxidant activity in vitro ³² and that they are absorbed efficiently in the body ³³ . However, their true antioxidant effect in humans is still controversial ³³ . According to some authors, the quantity of phenolic compounds in the diet is too low to protect LDL cholesterol (“bad” cholesterol) against oxidation ³³. On the other hand, other studies reveal that the consumption of olive oil rich in phenolic compounds could decrease oxidative stress in the body ^34-36 , an additional protection against the appearance of certain diseases, including cancer ³⁷ and cardiovascular disorders ³⁴ .
• Squalene . Compared to vegetables and other vegetable oils, olive oil contains high amounts of squalenes ^{38 , 39} , the latter being part of the large family of lipids. Once absorbed, squalenes are converted to cholesterol. They could be partly responsible for the increase in blood cholesterol sometimes observed following diets rich in olive oil ³⁹ . The long-term effect of squalenes present in olive oil should be studied in humans.

Canola oil

Canola is a variety of rapeseed, a plant in the cruciferous family. Canola is widely grown in Canada, particularly for the oil that is extracted from it. Compared to olive oil, canola oil has a more neutral taste and is more affordable.

According to the results of a large study of men suffering from coronary heart disease, a Mediterranean diet combined with a margarine based on canola oil could reduce recurrences of coronary incidents by 50% to 70% , compared on a low fat diet ⁴⁰ . Most clinical studies show that canola oil lowers LDL (“bad”) cholesterol and total ^{26 , 41,42} and triglyceride ⁴³ blood levels compared to a diet high in saturated fat.

Monounsaturated fatty acids . Like olive oil, canola oil is particularly rich in monounsaturated fatty acids . These account for almost 60% of the lipid content of canola oil. The effects related to the consumption of monounsaturated fatty acids have been described previously.

Polyunsaturated fatty acids . Canola oil stands out from olive oil and certain other oils by its high content of polyunsaturated fatty acids which represent almost a third of its total lipids. In general, these fatty acids have the effect of lowering blood cholesterol , particularly LDL cholesterol (“bad” cholesterol), when they replace saturated fatty acids in the diet ⁴⁴ . They thus help reduce the risk of coronary heart disease ^{24 , 45-47} .

• Alpha-linolenic acid . Alpha-linolenic acid (ALA) is part of the family of omega-3 polyunsaturated fatty acids. As this fatty acid cannot be manufactured by the body, it is said to be essential , because it must essentially be supplied by food. In the body, it can transform into long chain fatty acids , which are beneficial for cardiovascular health. Canola oil is one of the oils rich in alpha-linolenic acid (9% of its total lipid content), along with linseed oil (56%), nuts (10%) and soybeans (7% ). The protective effect of omega-3 fatty acids against coronary heart disease is well known. Some observational studies have shown the effectiveness of alpha-linolenic acid in this regard ⁴⁸. To take advantage of these benefits, the optimal daily intake of alpha-linolenic acid could represent up to 2 g (a serving of 15 ml or 1 tbsp of canola oil provides 1.3 g of alpha- linolenic) ⁴⁹ .

Antioxidants . Like most vegetable oils, canola oil contains antioxidants. Essentially, its antioxidant compounds differ from those of olive oil.

• Vitamin E . Canola oil contains 7 to 17 times more vitamin E than olive oil, about 17 mg per 15 ml serving, more than half of which is in the form of gamma-tocopherol ³⁰ . The refinement and deodorization stages of the oil partially reduce the vitamin E content of vegetable oils. This loss is often compensated for by adding synthetic tocopherols to the oil. According to a study, a diet rich in canola oil increases so that significant concentrations of gamma-tocopherol in blood compared to a standard or diet rich in saturated fats ⁵⁰ . Some studies show that high levels of gamma-tocopherol in the blood may have a protective effect against prostate cancer⁵¹ . More studies will be needed before establishing a link between the consumption of canola oil and cancer prevention.
• Canolol . An antioxidant called canolol was recently discovered in unrefined canola oil . ⁵² This compound prevents oxidation of lipids and proteins in vitro. New studies are needed to determine if these effects can occur in the body. It should be noted that most of the canola oils on the market are refined: they could therefore have a lower antioxidant capacity ⁵³ .

Phytosterols . Canola oil contains about 100 mg of phytosterols per 15 ml serving, two to seven times more than olive oil ^{38 , 54} . According to some data published in the scientific literature, the amount of phytosterols in the blood is higher after the consumption of canola oil than olive oil ^{38 , 54} .

Due to their close chemical structure, phytosterols hinder the absorption of cholesterol in the intestine. Hence an effect on blood cholesterol levels. A meta-analysis of 41 clinical trials found that daily intake of 2 g of phytosterols reduced by 10% the rate of LDL cholesterol ( “bad”) cholesterol. This reduction could reach 20% as part of a diet low in saturated fat and cholesterol ⁵⁵. This amount of 2 g per day is practically impossible to achieve only through food. Currently, Health Canada does not allow the marketing of foods fortified with phytosterols. Foods that naturally contain it like canola oil remain attractive for cardiovascular health.

Other properties

Most important nutrients

See the meaning of the nutrient source classification symbols

 Vitamin K . Canola oil is a good source of vitamin K while olive oil is a source . Vitamin K is necessary for the synthesis (manufacture) of proteins which participate in blood clotting (both in stimulation and in inhibition of blood clotting). It also plays a role in bone formation. In addition to being found in food, vitamin K is manufactured by bacteria present in the intestine, hence the rarity of deficiencies in this vitamin.

Vitamin E . Canola oil and olive oil are sources of vitamin E. It should be noted that vitamin E content is generally higher in first cold pressed oils than in refined oils. A major antioxidant, vitamin E protects the membrane that surrounds the cells of the body, especially red blood cells and white blood cells (cells of the immune system).

Source  : Health Canada. Canadian Nutrient File , 2005.
* EPA, DHA and Alpha-Linolenic Acid

Canola and GMOs
Most of the canola grown in Canada would be genetically modified. This practice is intended to make canola resistant to herbicides to facilitate weed control. It would help keep canola oil at a relatively low cost. Oils extracted from genetically modified canola, however, are not considered GMOs, as the typical components of GMOs ( DNAmodified and associated proteins) are not found there, except in the state of traces. Oils derived from genetically modified crops are therefore identical, in practice, to oils extracted and purified from traditional varieties that are found in common or organic products. Nevertheless, people who prefer to avoid consuming products from genetically modified crops can now find organic canola oil on the market.

Olive oil and weight gain
According to the results of a study, consuming olive oil as part of a Mediterranean type diet would not be associated with weight gain after two years of follow-up ⁵⁷ . Olive oil enhances the taste of salads and cooked vegetables, we often associate its addition with a higher consumption of vegetables ⁵⁸. This could help minimize the impact of the calories in olive oil. Weight gain, it should be remembered, results from a higher calorie intake than energy expenditure. If olive oil replaces other sources of calories in the diet and is not added in excess, it is possible to enjoy its health benefits without fear of weight gain. A similar conclusion could be made for canola oil. Indeed, in a study of men with coronary artery disease, there was no significant change in weight following the addition of a canola oil-based margarine in their diet ⁴⁰ .

Precautions

Canola oil can be hydrogenated or partially hydrogenated to withstand high cooking temperatures. Such an oil can be used in margarines, for frying or in various food preparations (pastries, chips, crackers, etc.), sometimes in combination with other oils, hydrogenated or not. It is important to detect the presence of hydrogenated or partially hydrogenated oils, in order to limit the consumption of trans fatty acids, known for their harmful effects on cardiovascular health ⁵⁶ .

The first fatty substances used were probably animal fats which were taken from terrestrial or marine animals slaughtered during hunting. Unlike vegetable oils, their preparation did not require a complex operation since it was enough to melt them. These fats were not used as much for food as for lighting, religious rituals, as a lubricant or even as a base for medicinal preparations. The dietary needs for lipids of our hunter-gatherer ancestors were rather covered by the very wide variety of grains and dried fruits rich in oil which they had in nature. Roasted whole over the fire or coarsely ground to make a kind of puree, these grains, of which we only consume a few varieties today,

Then, at some point in prehistoric times, the oil press was invented. It is not known exactly when to back this invention, but one found references to it in the Vedic scriptures of ancient India, while in the Mediterranean, the presses spread from 3 ^th  millennium BC time. The history of vegetable oils and their uses will be directly linked to technological advances which have made it possible, over time, to go from the rudimentary hand press to the modern expeller (or worm press) via gigantic work dug in the rock or built in stone, and fed by the current of a river.

The first oils will be those that are obtained from olives in the west and from sesame seeds in the east. Their extraction did not require any prior cooking and required only a relatively weak mechanical force, which could be provided by humans or draft animals. They will remain for a long time the only edible oils. They were used only sparingly, because they were expensive. Then add the oils of dried fruits – nuts, hazelnuts, cashews, pistachios, etc. – fruits of various palm trees – coconut palm, palm nut, palm nut – and, more recently, those of mustard seeds, rapeseed and cotton. With the advent of the industrial era, refining processes will be developed to extract oil from refractory materials at the simple cold press – soy, corn, grape seeds. In some cases, they will be deodorized to eliminate bitter principles which would otherwise limit their edibility. Oil which, until then, was mainly extracted mechanically in artisanal presses, will become a product of everyday consumption and, all things considered, its price will not stop falling.

Today, world production of vegetable oils and animal fats hovers around 75 million tonnes per year. While barely 50 years ago, soybean oil was only of marginal importance, it is now the largest source of dietary fat, although the oil content of soybeans is lower than that of other oilseeds: 18% to 20%, against 45% to 50% for palm nuts, 25% to 45% for sunflower and 35% to 60% for canola, the three other oils that follow it in importance.

In addition to consumer oils, there are artisanal oils on the market, i.e. oils that are pressed directly from the producer, who only markets a limited quantity of bottles each year. These local oils are appreciated by gourmets in the same way as good wines are, from which they borrowed the imaginary language. We are talking about a warm fragrance dominated by toasted bread and dried almonds, a strong identity, a rich attack or a good length in the mouth, a vegetal expression with a note of oak wood in background, etc.

Production methods

Mechanical pressure at the hydraulic press . It is the oldest method and the one that gives the oil closest to its natural state. The seeds or fruit are crushed, then cold pressed or slightly heated before being pressed, and the oil is then simply filtered or centrifuged to remove particles.

Mechanical pressure to expeller (or worm press). The materials are first heated to temperatures varying from 90 ° C to 120 ° C, then subjected to pressure. Although this is not always the case, the oil thus obtained is then generally refined, a process which includes many stages: filtration or centrifugation, laundering, deodorization, refrigeration, coloring, etc. Chemical preservatives are added to ensure the long shelf life of these products.

Extraction using chemical solvents. The materials are crushed, heated with steam, then mixed with a solvent (usually hexane, a petroleum by-product) which extracts the oil. The solvent is then separated from the oil by distillation and the latter is subjected to the various stages of the refining process. The temperature can reach 200 ° C or more during one or other of the refining stages. It is the method which makes it possible to obtain the greatest quantity of oil of a given substance and, consequently, to lower its selling price substantially. All oils not marked “virgin” or “extracted by pressure” are obtained by this method.

Many studies have been carried out over the past 50 years to modify the fatty acid composition of certain oils so that they have a better lipid profile. This is how we came across varieties of sunflowers whose seeds are richer in oleic acid (omega-9) and less rich in linoleic acid (omega-6) and palmitic acid (saturated fat).

Another trend in trade is also observed, namely the formulation of blends of oils with a lipid profile approaching values ​​perceived as ideal, for example the sesame, canola, olive and hazelnut blend, which is rich in monounsaturated and has a good omega-6 / omega-3 ratio.

More complex formulations are available in health food stores. They generally include linseed oil, sesame oil, sunflower oil and are added with borage oil, wheat germ oil, rice germ and oat germ. , medium chain triglycerides, lecithin, etc.

Choose well

Cold pressed oil should be neither too light nor too dark. If the oil is translucent, it is because it has been refined, and if it is very dark, it is because it has been preheated or pressed at high temperature. Its aroma and taste should recall those of the oilseed from which it comes. In order to limit the deleterious effects of light, good oils are packaged in opaque bottles (or other types of containers), mostly in glass, sometimes in metal or plastic. The expiration date or production date should be written on the label.

Culinary dishes

Edible oils can be prepared in an infinite number of ways. Here are a few.

• Use cold pressed oils , preferably raw, in lukewarm or cold salads, on bitter raw vegetables (chicory, endive, radicchio), on grilled vegetables, potatoes in field dress or mash, whole cereals , pasta, sundried or sundried tomatoes, corn kernels, polenta, cream cheese, scallop or smoked salmon carpaccio, seafood, or in marinades.
• We can also add them at the end of cooking to stir-fry dishes or in dishes that will cook in the oven, especially those that do not require a high temperature, pastries for example, in which oil of nuts, hazelnuts, almond, pistachio, sesame or pine nuts will do wonders.
• Very good olive oils are served simply poured into a dish and seasoned (or not) with a hint of a good vinegar, as an accompaniment to the starter or main dish. You dip your bread in it.
• As it is odorless, grapeseed oil constitutes a good base to which one can add very tasty oils, the flavor of which one wishes to attenuate. In addition, as it captures the aromas well, it can be used to prepare macerations with herbs  : finely chop the herbs of your choice, add them to the oil and leave to macerate for a few days or even a few weeks.
• You can use the oils to emulsify a sauce, a coulis, a soup (minestrone for example), a court-bouillon, or to make a mayonnaise.
• Spread hummus on a plate, creating a kind of small pond in the center into which we will pour a drizzle of olive oil or sesame. Serve with flat spelled bread.
• Jar goat cheese with good olive or walnut oil, thyme, rosemary, savory and pepper, refrigerate and wait until the cheese is soft before eating.
• Garlic croutons: cut pieces of stale bread into cubes, brown them in olive oil until they are well toasted, drain and rub each of them with a clove of garlic . Serve these croutons in soups or in a chicory salad.
• Grill on the barbecue or in the oven: before grilling, place pieces of meat, fish or vegetables in an olive oil or an oil in which garlic and herbs have been marinated.
• In pancake, waffle, cake and cookie preparations .

All oils except linseed oil can be stored out of the fridge, in a cool, dry place and away from light. Their average shelf life before opening is approximately one year. In general, saturated and monounsaturated oils keep longer than polyunsaturated oils, which are less chemically stable and have poor resistance to oxygen and heat. Unless used daily, store unrefined oils in the refrigerator once started.

Flaxseed oil can be stored in the refrigerator at all times, for four months if the bottle is sealed, and four weeks after it is opened.

Freezer: oils can be frozen to extend their shelf life.

Currently in full swing, the field of biofuels is of interest to researchers and industrialists wishing to find alternatives to fossil fuels, which are not renewable, and incidentally, to free themselves from energy dependence on petroleum.

However, many environmentalists question the merits of green fuels (which are made from alcohol, vegetable oils or a mixture of alcohol and oils), the plants used to make them generally very demanding in chemical fertilizers (themselves petroleum by-products) and sometimes a source of pollution.

On the other hand, there are situations where biofuels could be more ecological. So it is with pourghere oil ( Jatropha curcas), a tropical shrub of the euphorbiaceae family whose seeds provide a high proportion (40%) of an inedible oil, traditionally used in medicine and to make soap. The advantage of the perghere is that it is easy to maintain, does not require fertilizer and resists drought. Being content with marginal land, too poor for food crops, it does not compete with plants intended for human consumption, which require richer land. Because of its smell, animals do not touch it, so that farmers generally plant it in hedges around their fields or gardens, in order to protect crops. In addition to preventing animals from accessing the fields, these hedges fight against wind and water erosion.

With its 10,000 km of perghere hedges and an annual growth rate of 2,000 km, Mali has an oil production potential of nearly 1,700,000 liters per year. We already know many technological applications. Thus, in Kelaya, a village of 3,000 inhabitants where, until recently, there was no electricity, it is now lit thanks to the current produced by a generator powered by this fuel.

As a bonus, the oil cake that remains after the oil is extracted is an organic fertilizer of very good quality, whose mineral composition is comparable to that of chicken manure. For agriculture in Sahelian countries, where humus is scarce, it is an excellent alternative to chemical fertilizers, too expensive for the vast majority of farmers.