Περιγραφή
For many years garlic has been used as a means of treating various diseases, while recently it was found that it reduces the occurrence of cardiovascular diseases and neoplasms, and has a strong antimicrobial effect. Sulfur compounds, specifically the substance allicin, appear to be the active ingredients of garlic. Available evidence reveals that garlic has been used for about 5,000 years, with 3,000 years of use in China in the field of medicine. Historically, garlic has been used around the world to treat a host of ailments, including high blood pressure, infections, and poisonous snake bites.
Therapeutic action
The bulb of garlic is used for medicinal purposes. It can be used fresh, dehydrated, or as an extract. Garlic has a high concentration of sulfur compounds, which are the active substances. The main substances that garlic contains are alliin and alliinase. These two substances are found in garlic separately and are not connected to each other. When the clove of garlic breaks, these two substances combine to form allicin. Allicin is the substance that gives garlic its characteristic smell and taste. For this reason, it is necessary to crush garlic before adding it to food, in order to release the active allicin. According to research, allicin is toxic to cancer cells. However, stomach acids and heat inhibit the enzyme action of allinase, resulting in less allicin being formed and consequently, garlic in cooked form has a less potent healing effect.
Garlic's antimicrobial, anti-thrombotic and antioxidant properties, as well as its ability to lower blood lipid levels, have been attributed to the substance allicin. The anti-neoplastic properties are likely due to sulfur compounds or other components of unknown chemical composition and structure.
Uses and effectiveness
The properties of garlic have been extensively studied in human and animal clinical trials, as well as in epidemiological studies. Results in human trials have varied. Some research protocols were not well organized, due to the short duration of the intervention, the small sample and the different processing method of the garlic, which resulted in the release of the active ingredients in different quantity and quality.
Ability to lower blood lipid levels
Several randomized clinical trials have studied the effectiveness of garlic in reducing blood lipid levels. Results from two analyzes carried out in 1993 and 1994, on the effect of garlic on total blood cholesterol, showed a significant reduction in the level of total cholesterol (9 -12%), compared to a placebo sample. However, additional trials, performed later and better designed, showed conflicting results.
An analysis carried out in 2000 that reviewed these trials concluded that garlic lowers cholesterol levels to a greater extent than placebo preparations, but the overall effect is modest (4-6%). A more recent analysis of trials using standardized garlic powder showed significant reductions in total cholesterol, LDL cholesterol and triglyceride levels over 8 to 12 weeks. The discrepancy in the percentage of reduction may be due to the differences between the studies. A European trial comparing garlic to a commercial drug for lowering the level of lipoproteins in the blood found it to be just as effective.
Antihypertensive action
Garlic's ability to lower blood pressure values has been studied, but remains in doubt. In 1994, several studies were analyzed and the effect of garlic on hypertension was evaluated. In three trials there was a significant reduction in systolic blood pressure (by 7.7mmHg), and in four trials there was a reduction in diastolic blood pressure (by 5mmHg) with taking garlic, versus a placebo drug.
In a more recent analysis, however, 23 placebo-controlled trials were examined. Only three trials showed a statistically significant reduction in diastolic blood pressure (2-7%), and one study showed a reduction in systolic blood pressure (about 3%) in patients who consumed garlic, versus a placebo drug.
Antitumor effect
Epidemiological evidence from individual controls and some cohort studies has shown a reduced risk of stomach and colon (large intestine) cancer with increased consumption of garlic and other vegetables with similar ingredients (eg, onions, leeks, scallions) ). However, many of these studies were not well designed. In one group study, taking garlic supplements did not provide the same benefit. However, there are no studies evaluating garlic supplementation and cancer incidence.
Contraindications - Interactions
Eating one to two cloves of raw garlic per day is considered safe for adults. The most common unpleasant consequence of garlic is breath and body odor . Eating too much raw garlic, especially on an empty stomach, can cause gastrointestinal upset and changes in intestinal motility. There have been reports of allergic dermatitis, burns, and rashes from topical application of raw garlic.
Garlic appears to have no effect on drug metabolism, although recent studies in healthy volunteers show conflicting results regarding the effect of garlic on the action of drugs with protease inhibitors. It has been suggested that patients taking anticoagulant drugs should exercise caution when consuming garlic, as it exhibits anti-thrombotic properties.
