Garlic has been used for several hundred years to treat a variety of health problems. A large number of studies have been carried out to better understand the active ingredients in garlic and their physiological effects. In these studies, garlic is used in different forms: fresh, dehydrated, as well as as an extract, oil or tincture.
Several prospective and epidemiological studies have shown that a high consumption of vegetables and fruits decreases the risk of cardiovascular diseases, certain cancers and other chronic diseases. More specifically, studies have shown that the consumption of vegetables from the alliaceae family (garlic, onion, shallot, chives, scallions, leeks) has a protective effect against cancers of the stomach and intestine. However, to date, there is insufficient data to establish a link with other types of cancers such as prostate, breast, esophagus and lung cancers.
Garlic has been found to have a beneficial impact on the following diseases:
Several epidemiological studies indicate a positive effect of the consumption of garlic on the prevention of certain cancers. 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 approximately 50% in the risk of stomach cancer in the event of high consumption of garlic. Among all the studies noted, such consumption was equivalent to approximately 18 g of raw and cooked garlic per week (or about six cloves). Since the amounts ingested varied greatly from study to study, it is difficult to determine more precisely the minimum amount of garlic to consume in order to benefit from its effects on colorectal and stomach cancer. Other studies have found an inverse relationship between garlic consumption and the incidence of laryngeal, prostate and breast cancer. However, no general conclusion can be drawn for the moment, given the insufficient number of studies on the subject.
Garlic may also slow the development of certain cancers, both through its protective action against damage caused by carcinogens and through its ability to prevent cancer cells from growing. The sulfur compounds contained in garlic could play an important role. Thus, garlic, at the rate of a consumption of two cloves per day (approximately 6 g of garlic), is part of a list of foods containing molecules with anticarcinogenic potential to be favored in an optimal diet aimed at prevent cancer. It is important to remember that one 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.
According to several studies, garlic extracts rich in active ingredients, in particular in allicin, make it possible to reduce blood cholesterol and triglyceride levels. The adenosine contained in the cloves of garlic has a small vasodilator effect, which allows better blood circulation and could, moreover, also explain the anti-hypertensive effect of garlic. In addition, garlic contains prostaglandins which have the property of thinning the blood, which can further improve blood circulation.
Compounds found in garlic also help reduce atherosclerotic plaques, according to the WHO. These plaques, composed in particular of cholesterol, are deposited over the years on the walls of the arteries, making them more rigid and reducing their diameter. This pathology therefore constitutes a risk factor for cardiovascular incidents. Several studies have shown that the disease progresses three times slower in people at risk consuming garlic than in people at risk not consuming it. Garlic seems particularly well to protect the aorta, the central artery of our body. Regular consumption of garlic would therefore reduce the risk of cardiovascular mortality.
Garlic may be a great way to preserve memory and cognitive skills, according to a study conducted at the University of Louiseville in the United States. It would act by renewing the intestinal microbiota, the latter being directly connected to the brain by the vagus nerve. It is again a sulfur compound which would be responsible for this beneficial effect on the brain.
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 achieve with usual consumption of fresh garlic.
In a study carried out in a population of a region of China, a high consumption of garlic (more than 5 kg per year per person, or the equivalent of about four to five cloves of garlic per day) was weakly associated with a decrease in infections with Helicobacter pylori. However, this observation was disputed by a clinical study in which people ate ten fresh garlic cloves per day, with no significant effect against H. pylori infection.
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 in the group with the garlic supplement had fewer cold episodes than those who took the placebo. In addition, when they had a cold, the individuals who were in the group with the garlic supplement saw their symptoms decrease more quickly than those who took a placebo. For the moment, the data are still insufficient to confirm that the consumption of fresh garlic has an anti-infective effect in the body.
Beneficial active ingredients found in garlic
Garlic contains many active compounds, which provide different health benefits. Some of these compounds are assigned several roles. This is the case, among others, of sulfur compounds, associated with both the prevention of cancer and cardiovascular disease. It should be noted that not all of the phytochemicals in garlic are active in the body and that some have yet to be discovered. It should also be noted that the active ingredients contained in fresh garlic work synergistically to produce various health effects.
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 mashed. At this point, alliin (an inactive, odorless molecule in garlic) comes into contact with an enzyme and turns into allicin, which is the molecule responsible for the characteristic scent of garlic. Subsequently, allicin is transformed into other sulfur compounds such as diallyl sulfide, diallyl disulfide and ajoene. It is mainly these compounds that could prevent certain cancer cells from multiplying and thus protect the body against potential carcinogens. It should be noted that during the manufacture of garlic tablets, allicin would be destroyed, so the consumption of garlic tablets would not allow the ingestion of theses active compounds beneficial to health.
In some studies, allicin has been proposed as the main active compound associated with the cardioprotective effect of garlic, among other things through its ability to reduce atherosclerotic plaques in animals. However, when one takes into account the fact that allicin is not absorbed into the blood during consumption of garlic, it is unlikely to contribute as such to the effect on cardiovascular health. Rather, allicin is a transient compound rapidly transformed into other sulfur compounds which, in turn, are active in the body. Finally, ajoene is thought to be a compound capable of preventing the synthesis (formation) of cholesterol in vitro and may thus play a role in the hypocholesterolemic effect attributed to garlic.
Antioxidants are compounds that protect cells in the body from damage caused by free radicals. The latter are very reactive molecules that are believed to be involved in the development of cardiovascular diseases, certain cancers and other diseases linked to aging. Garlic contains various antioxidant compounds such as flavonoids and tocopherols, in addition to sulfur compounds which are said to also contribute to its antioxidant activity.
Saponins are compounds found in garlic that have the ability to lower blood cholesterol in animals and blood clotting in vitro, two effects sought to prevent cardiovascular disease. In addition, it has been shown in animals that the isolated garlic protein may have a lipid-lowering effect. These promising compounds could therefore be associated with the cardioprotective effect of garlic, but more studies are needed to better understand their roles.
Raw or cooked garlic
To preserve all the virtues of garlic, it is advisable to consume it raw, finely chopped. Allicin is then present in large quantities. During cooking, on the other hand, it loses in potency and it is estimated that it is necessary to approximately triple the amount of garlic to obtain the same benefits. Not everyone digest raw garlic very well. In this case, the solution is to add it a few minutes before the end of cooking: it will no longer be completely raw but will retain most of its properties. Avoid, however, letting it carbonize: it would then become more toxic than anything else.
How much garlic to consume per day?
To benefit from its positive effects on blood lipemia (cholesterol, triglycerides, etc.), it is a daily consumption of one to two cloves of fresh garlic is recommended, or 0.5 to 1 g of dried garlic.
For its anti-cold and cough effect: the recommended dose is 4 fresh garlic cloves or 2 to 4 g of dried garlic per day.
While garlic is excellent for your health, care must be taken not to overdo it, at the risk of suffering from heartburn or abdominal cramps. Consumed in large quantities, garlic can also cause bad breath. On this last point, know that the smell usually disappears after a few hours and the chewing of a little parsley counteracts this effect. Brushing your teeth does not change much, however, since the smell comes from the gases released by chewing and then digestion.
Born in London, England and raised in Orlando, FL, Elena graduated from the University of Central Florida with a bachelors’ degree in English. She later received her masters’ in Creative Writing from Drexel University. She writes part-time for the Scientific Origin and focuses mostly on health related issues.