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All about Garlic

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Health profile

The garlic has been used for hundreds of years to treat various health problems. A very large number of studies have been carried out in order to better understand the active principles of garlic and their physiological effects. In these studies, garlic is used in different forms: fresh, dehydrated, as well as in the form of an extract, oil or tincture. Note that this fact sheet is only dedicated to the effects of eating fresh garlic (raw or cooked) as used in various food preparations.

Garlic: understand everything in 2 min

Active ingredients and properties

For vegetables of the Alliaceae family
Several prospective and epidemiological studies have shown that a high consumption of vegetables and fruits reduces the risk of cardiovascular diseases, certain cancers and other chronic diseases , 2 . More specifically, studies have shown that the consumption of vegetables from the alliaceae family (garlic, onion, shallots, chives, spring onions, leeks) would have a protective effect against stomach and intestinal cancers , 4 . To date, there are insufficient data to establish a link with other types of cancer such as prostate, breast, esophagus and lung cancer4 .

Cancer Garlic
 . Several epidemiological studies indicate a positive effect of the consumption of garlic on the prevention of certain cancers 5 . First, the results of a meta-analysis of 18 epidemiological studies published between 1966 and 1999 demonstrate a 30% reduction in the risk of colorectal cancer and an approximately 50% reduction in the risk of stomach cancer in the event of high consumption of garlic 6 . Among all the studies identified, such consumption was equivalent to approximately 18 g of raw and cooked garlic per week(about six pods). Since the amounts ingested varied greatly from one study to another, it is difficult to determine more precisely the minimum quantity of garlic to consume in order to benefit from its effects on colorectal and stomach cancers. Other studies have observed an inverse relationship between the consumption of garlic and the incidence of cancers of the larynx , of the prostate , and within. However, no general conclusion can be drawn for the moment, given the insufficient number of studies on the subject 6 .

Garlic: raw or cooked?
The enzyme found in garlic that allows the formation of allicin and other sulfur compounds is deactivated by heat 19 . Depending on the mode and cooking time of the garlic, the sulfur compounds formed will be different and the amount of antioxidants may decrease 29 , 37 . The properties of raw garlic would therefore be superior to those of cooked garlic 19 . Tip: add the garlic 20 minutes or less before the end of cooking to preserve the quality of its active compounds as much as possible 38 .

Garlic could slow the development of certain cancers, both by its protective action against damage caused by carcinogens and by its ability to prevent cancer cells from growing 11 . The sulfur compounds in garlic could play an important role (see Active ingredients) 5 . Thus, garlic, at the rate of a consumption of two cloves per day (or approximately 6 g of garlic), is part of a list of foods containing molecules with anticarcinogenic potential to be preferred in an optimal diet aimed at prevent cancer 11. It is important to remember that a food alone cannot be effective in protecting against cancer. A varied and constant consumption of several foods with preventive potential as well as the maintenance of a healthy lifestyle are essential elements.

Cardiovascular diseases . The American Heart Association (AHA) publishes dietary recommendations to prevent the risk of cardiovascular disease, such as high consumption of fruits and vegetables, as well as the choice of whole grain cereal products and low fat dairy products 12 . Based on numerous research results, the AHA offers a list of specific foods with some cardioprotective effect. Garlic is one of these foods (just like nuts, soy, legumes and tea) and its consumption is therefore added to the basic recommendations of the AHA with a view to preventing cardiovascular disease.

The majority of studies evaluating the effect of garlic on risk factors for cardiovascular disease (such as blood pressure, blood cholesterol and glucose) have been carried out with supplements or extracts of garlic, in order to isolate active ingredients. Overall, this research demonstrates a tendency to slightly lower blood cholesterol and triglyceride levels . Few studies have therefore evaluated the real impact of consuming fresh garlic (raw or cooked) on these risk factors and they date from a few years ago. In two of these studies, the daily consumption of 3 g and 10 g of fresh garlic for 16 and 8 weeks respectively contributed to a decrease in total cholesterol 13 , 14. More studies are needed to assess the effect of consuming fresh garlic on the prevention and treatment of cardiovascular disease 15 . According to the results of studies using garlic extracts, a daily consumption equivalent to 2 g to 5 g of raw garlic or to 10 g to 15 g of cooked garlic would be necessary in order to benefit from benefits on certain factors risk of cardiovascular disease such as total cholesterol, LDL cholesterol (“bad” cholesterol) or high blood triglycerides 16 .

Infections . Garlic is traditionally used for its antimicrobial properties and for the treatment of certain infections. The majority of studies on the subject have been carried out using garlic extracts, in doses that are often difficult to reach with the usual consumption of fresh garlic. In a study carried out on a population of a region of China, a high consumption of garlic (more than 5 kg per year per person, the equivalent of approximately four to five cloves of garlic per day) was weakly associated with a decrease in infections with the bacterium  Helicobacter pylori 17 . This finding was disputed by a clinical study in which people consumed ten fresh cloves of garlic per day, with no significant effect against infection H. pylori 18 . Some studies suggest that garlic may help prevent colds. In fact, in one study, two groups were compared: one consumed a garlic supplement and the other a placebo for 12 weeks during the cold season (November to February). The results show that those who were in the garlic supplement group had fewer cold episodes than those who took a placebo. In addition, when they had a cold, the individuals who were in the group with a garlic supplement saw their symptoms decrease faster than those who took a placebo. For the moment, the data are still insufficient to state that the consumption of fresh garlic would bring an anti-infectious effect in the body 19 .

Beneficial active ingredients

Garlic contains many active compounds, which bring different health benefits. Some of these compounds are assigned multiple roles. This is the case among others of sulfur compounds, associated with both the prevention of cancer and cardiovascular disease. Note that the molecules phytochemicals in garlic are all active in the body and some are yet to be discovered 20 . Note that the active ingredients in fresh garlic work synergistically to produce different health effects.

Sulfur compounds . These substances are so named because they contain one or more sulfur atoms in their chemical structure. Sulfur compounds are released when garlic is  cut, crushed or crushed 19 . At this point, alliin (an inactive and odorless molecule of garlic) comes into contact with an enzyme and turns into  allicin , which is the molecule responsible for the characteristic smell of garlic. Subsequently, the allicin is transformed into other sulfur compounds such as  diallyl sulfide ,  diallyl disulfide  and  ajoene . It’s mainly these compounds that could prevent certain  cancer cells to multiply and thus protect the body against potential carcinogens 11 , 21 . It should be noted that during the manufacture of garlic tablets, the allicin would be destroyed, which means that the consumption of garlic tablets would not allow the ingestion of the active compounds beneficial to health.

In some studies, allicin has been proposed as the main active compound associated with the cardioprotective effect of garlic 22 , among other things by its ability to reduce atherosclerotic plaques in animals 23 . On the other hand, when you take into account that allicin is not absorbed into the blood during the consumption of garlic, it is unlikely to contribute as such to the effect on cardiovascular health 20 . Allicin would rather be a transient compound quickly transformed into other sulfur compounds which are active in the body 20 . Finally, the ajoeneis a compound capable of preventing the synthesis (formation) of cholesterol in vitro 24 and could thus play a role in the cholesterol-lowering effect attributed to garlic.

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 25 . Garlic contains various antioxidant compounds such as flavonoids 26 and tocopherols 27 , in addition to sulfur compounds which would also contribute to its antioxidant activity 28 . Consumption of fresh garlic (raw or cooked)would increase antioxidant activity in plasma in rats 29 , but daily consumption of 3 g to 6 g of raw garlic for seven to eight days in humans did not confirm this observation 30 , 31 . We all the same know that at equivalent weight, garlic has a higher antioxidant capacity than a wide selection of vegetables 32 , 33 . On the other hand, when the frequency and size of the portion usually consumed are taken into account, the impact of garlic consumption on the total antioxidant capacity remains limited, compared to other vegetables consumed in larger quantities 33 .

Other compounds . The saponins are compounds present in garlic that have the ability to lower blood cholesterol in animals 34 and blood coagulation in vitro 35 , two desired effects for the prevention of cardiovascular disease. In addition, it has been shown in animals that the isolated garlic protein could have a lipid-lowering effect 36 . These promising compounds could therefore be associated with the cardioprotective effect of garlic, but more studies will be needed to better understand their roles.

Other properties

Is garlic antioxidant? We know that fresh garlic contains certain antioxidants, but currently its TAC index is not available.
Is garlic acidifying? Data not available.
Does garlic have a high glycemic load? No.

Most important nutrients

What is a “portion” of garlic worth?
Weight / volume Raw garlic, 3 g / 1 clove
Calories 4
Protein 0.2g
Carbohydrates 1.0 g
Fat 0.0 g
Dietary fiber 0.1g

Source  : Health Canada. Canadian Nutrient File , 2005.

Consumed in small quantities, garlic provides few nutrients. By cons, consumed in larger quantities during the day, garlic turns out to be a source of some nutrients. For example, a bulb of garlic (about 40 ml or 24 g of garlic) is a good source of manganese and vitamin B6, as well as a source of phosphorus (see our fact sheet Phosphorus nutrients ), iron , copper , selenium and vitamin C.


Interactions with certain medications
Garlic extracts or supplements interact with certain medications that thin the blood or have an anticoagulant effect. Likewise, consuming excessive amounts of fresh garlic while taking certain anticoagulant medications may cause an additive effect, increasing the risk of bleeding . 19 In addition, it is advisable to avoid consuming garlic before surgery in order to reduce the risk of prolonged bleeding. Finally, in people taking hypoglycemic drugs , consuming large amounts of fresh garlic may increase the effect.of these drugs. In general, the consumption of less than 4 g of garlic (the equivalent of a clove) per day seems prudent in order to avoid any harmful interaction.

Garlic side effects

  • Garlic can change the taste of breast milk. The nursing women should watch their intake of garlic during this period 16 .
  • Consuming a high and regular amount of garlic could affect blood glucose; people with diabetes should pay special attention to it 16 .
  • Excessive consumption of raw garlic, especially when the stomach is empty, can cause gastrointestinal disorders  : the ingestion of one to two cloves of garlic per day is a safe dose for an adult 19 .

Garlic preserved in oil
Garlic can be preserved in oil, which prolongs the shelf life. On the other hand, it is possible that the garlic contains a bacterium responsible for botulism . Thus preserved in oil (without oxygen), the conditions are optimal for the development of toxins. Consumption of a deteriorated product can lead to severe food poisoning which manifests itself in symptoms such as dizziness, blurred or double vision, difficulty in breathing, swallowing and speaking. The appearance, smell and taste of a deteriorated oil will not necessarily be modified, hence the importance of respecting the following instructions:

  • Always keep garlic stored in oil in the refrigerator .
  • Consume immediately or within a week of homemade garlic oil. Commercial garlic oils should contain preservatives (acids, such as vinegar, or salt): check on the product label.

Garlic over time

The term ”  garlic  ” comes from the Latin allium . It could derive from a Greek word meaning “to spring from”, by allusion to the very fast way that the bulb has to divide into several cloves, which literally seem to spring from it. Others think it comes from Celtic all , which means “spicy”.

The center of origin of garlic is said to be a large crescent (the “garlic crescent”) which extends from the Caspian Sea in the west to the Tian Shan Mountains on the border with China. and Kazakhstan to the east. In this vast region, there are approximately 150 wild species belonging to the genus Allium . However, the wild ancestor of cultivated garlic ( Allium sativum ) has not been found .

The stinking rose
Shakespeare considered that garlic was not made for the nobles and Cervantes recommended not to eat either onion or garlic at the risk that their smell would betray a deplorable peasant origin. “Stinking rose”, “imprint of Satan’s left foot”, the most vehement qualifiers have never failed to describe it.

The oldest writings on its culture date from the Sumerians (2,500 BC), but it was consumed long before as a spice or remedy. Known to the Egyptians, the Greeks and the Romans, it will spread in the south and east of Europe. It will not enjoy the same glory in the northern countries and in the British Isles, except sometimes as a medicinal plant in the gardens of monasteries.

Transported by sailors who always keep it to protect themselves from epidemics and the evil eye, it will reach the Dominican Republic with Christopher Columbus and will then spread throughout South and Central America. However, it was not until the XIX th  century it will arrive in North America, under the influence of Mexican cuisine, which is very fond of. It will find fertile ground in California, particularly in the Gilroy Valley, where it will be cultivated on a large scale and where one will not hesitate to grant oneself the status of “international capital of garlic”.

Culinary uses

To access other recipes, you can go to the kitchen recipes site, which offers, among others, the following recipes : garlic-based recipes , Garlic soup, Garlic bread

Choose well

Garlic with soft stems and garlic with hard stems
The garlic commonly sold in America belongs to the subspecies Allium sativum  var. sativum , which is characterized botanically by the absence of a flower spike (hence its name “garlic with tender stem”) and numerous small pods.

Garlic myth.
Brushing your teeth after eating garlic reduces bad breath.Reality . Brushing your teeth has no effect on garlic breath, since the characteristic smell comes from the gases released in the mouth during chewing, then in the digestive tract throughout digestion. These gases take at least three hours to be eliminated. The only way to reduce your breath a little after a meal is to chew parsley, mint or coffee beans.

From a culinary point of view, the subspecies Allium sativum var. ophioscorodon , which has a flower stalk (hence its name “hard- sided garlic” or even “stick garlic”) and fewer and relatively larger pods, is clearly superior. This subspecies is believed to be the older of the two and has retained some of the characteristics of wild garlic, including its flavor and, unfortunately, its short shelf life. Preserved over the centuries thanks to the care of experienced amateurs, stick garlic is offered today through networks of artisan producersas well as by a few specialized shops. In Europe, where it is better known, it is not uncommon for it to be considered as a local product. This is the case with Lautrec’s pink garlic , which in France benefits from a controlled designation of origin.

Garlic Rocambole
This type with a hard stem is particularly tasty, but not always easy to find.

False garlic
What in Quebec is called “elephant garlic” and, in France, “eastern garlic” is not garlic, but a kind of leek that is generally prepared in the same way, although it has neither the strong flavor nor the virtues of garlic.

Culinary dishes

In order to properly remove the garlic peel, it is crushed with the dish of a knife. We then remove the germ that would make the garlic indigestible and that would be largely responsible for bad breath.

  • Aillet  : thus called the garlic grows out of the earth in spring and that has not yet begun training its bulb. It is eaten in a croque-au-sel or slightly steamed and drizzled with a vinaigrette, as for the leek. You can also mince it in salads, soups, etc. Look for this product on the side of Asian grocery stores.
  • Flower stalk  : in order to favor the production of the bulb, the flower stalk of garlic, with its flower bud, must be cut shortly after its formation. Finely chopped, it is used in all kinds of preparations, such as garlic butter . It can be found in jars in delicatessens.
  • Garlic in shirt  : roasted or roasted in the oven in its skin, garlic acquires a very particular flavor which will enhance mayonnaises, vinaigrettes or hot sauces. The entire bulb will first be topped and brushed with oil. You can also add the individual pods to a broth or sauce and remove them when ready to serve, or stuff the poultry for roasting. At the end of cooking, we can collect the garlic and make a sauce.
Who loves me follows me
In the opinion of some good eaters, the only really effective method to avoid annoying those around him with sulfurous breath is to convince him to eat garlic at the same time as himself …
  • Ailloli  : it mounts like mayonnaise with the exception that you start with crushed garlic before adding the usual ingredients. It can accompany a fish, cold meat or a fondue. If we add a piece of bread crumbs soaked in fish stock and red Spanish peppers, we get a rust , traditionally served in Provence with bouillabaisse.
  • Aïgo-bouïdo  : of the many recipes for garlic soups developed around the world, one of the simplest is aïgo-bouïdo, for semi-culinary, semi-medicinal uses. To prepare it, cook six crushed garlic cloves in one liter of boiling water for about ten minutes. Then remove from heat, add sage, thyme and bay leaf and let steep for a few minutes. Remove the herbs, beat an egg omelet and add it to the soup without ceasing to beat. Salt and pepper. Thias broth is served on a slice of bread drizzled with oil.
  • Pasta  : brown whole garlic cloves in oil, then remove the garlic and coat the pasta with this fragrant oil. Others simply prefer to add crushed garlic to very hot noodles with a little melted butter or olive oil.
  • Bitter salad with garlic  : dandelion, chicory, escarole, raddichio, Treviso lose some of their bitterness and are improved when served with croutons returned in olive oil and rubbed with garlic. Drizzle with warm dressing to soften the greens, and add bacon, if desired.
According to a garlic lover who was definitely not lacking in humor, “a five-cent coin may allow you to take the train, but garlic will guarantee you a seat.”
  • Garlic butter  : serve frogs’ legs, shrimps and snails covered with butter which has been kneaded with garlic, shallots and parsley, finely chopped. Spend a few minutes in the oven on high heat. Mussels can be cooked in butter, with garlic, herbs and white wine, covering, until they open. Reduce the liquid over high heat and coat the molds.
  • Garlic bread  : cut a slightly stale baguette into slices without completely detaching the slices. Insert the butter handled with chopped garlic and salt between the slices. Lock the baguette in aluminum foil, put in the oven on medium heat and bake 20 or 30 minutes.


Depending on the variety, fresh garlic will keep for three to nine months. Keep it dry at room temperature, since cold and humidity have the effect of triggering the germination process.

Organic gardening

In Quebec, garlic is sown between September 15 and October 15, and harvested in July of the following year. For flower bed cultivation, the ideal spacing is 12 cm by 20 cm. For row cultivation, the plants should be spaced 15 cm apart, and the rows 20 to 25 cm apart. To ensure that the garlic survives the vagaries of winter, it is recommended to cover it with a very thick mulch (dead leaves, straw or old hay). Remove the mulch in April or May to allow the soil to warm up and the plants to take off, then put it back again to prevent the emergence of weeds, against which the garlic, with its narrow leaves, is defenseless.

To promote bulb growth, the flower stalks of stick garlic varieties will be cut at the latest when it reaches 15 cm (around mid-June in southern Quebec). We can let some flower stalks grow: their deployment is a spectacle in itself and, moreover, we can harvest the bulbils which will form later at its end to use them as seeds or in food. By the way, it is for hens, who love it (from the bulb and bulbils), an almost infallible means of reducing the incidence of infectious diseases in the henhouse, in particular salmonellosis.

The harvest is done from mid-July to mid-August depending on the varieties and regions, either when five or six green leaves (out of the original ten) remain on the stem. The whole plant, with its leaves and roots, will be hung in the dry and in the shade for a period of two to four weeks in order to complete the ripening and drying process of the bulbs. At harvest time, you absolutely must resist the urge to wash the bulbs, at the risk of hampering the ripening process. Once the bulbs are completely dry, cut the roots flush and the stems two or three centimeters. Set aside the medium sized pods for the seed making sure they are all very healthy.

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