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Health benefits of garlic



Garlic (Allium sativum), a plant native to central Asia, has been used since thousands of years ago for culinary and as medicinal purposes, being part of ancient natural remedies for the treatment of some of the most common ailments and illnesses, as well as for some of its health benefits and properties, among which we can mention being a natural expectorant and an anti-microbial agent

Sumerians, Chinese, ancient Indians, Egyptians, Romans, Greeks, Tibetans, Slavic, Arabic and the list goes on and on naming hundreds of cultures that used garlic not only for its known culinary properties but for its health benefits and as a well-trusted universal folk remedy for the treatment of various illnesses and ailments. 

Some cultures still know garlic as ‘Russian penicillin’, ‘natural antibiotic’, ‘vegetable viagra’, ‘plant talisman’, ‘rustic's theriac’ and ‘snake grass’ [5,6]. Image: Garlic by Mo Riza under Creative Common license (CC BY 2.0). 


Family: Amaryllidaceae

Genus: Allium

Common name: Garlic



In the past, garlic was used as a folk remedy during various epidemics such as typhus, dysentery, cholerainfluenza, and whenever an epidemic has emerged. Garlic has been the first preventive and curative remedy [5,6].

Now, back to the subject, who didn't hear about the saying that onions and garlic collect and kill the flu (influenza) virus spread since its origins time ago in 1919?

I found it interesting enough to enter a little bit deeper and see if there were probably other reasons to believe garlic and onions really got this claimed antiviral and anti-bacterial properties. But let's see what we found about Garlic (Allium sativum) and onion (Allium cepa), it may surprise some of us at the end. 



But if we talk about the benefits of garlic we shall also mention some of its inconveniences. Garlic is rich, as we will see a little bit later in this article, in sulfurous compounds, more exactly organosulfur compounds.

These organosulfur compounds, which by the way are responsible for the benefits of garlic, are also responsible for its flavor and aroma, being the principal factor why garlic exerts such a characteristic and not very pleasant smell.

As you can realize, if organosulfur compounds are responsible for the health benefits of garlic, this will mean that the strongest the smell of garlic the more benefits garlic will exert, and this seems to be the case, so what a dilemma, if you like to profit from the benefits of garlic you'll need to suffer from its unpleasant aroma, or not?

Well, it seems that pharmaceutical companies thought about that and have created what they call odorless garlic extract, a concentrate of organosulfur compounds from garlic without the unpleasant aroma garlic exerts.



Garlic is reproduced from cloves and it can be cultivated in under many different climatic conditions, however it can't withstand either too hot or too cold climates, being ideally grown in Mediterranean areas where it is commonly used as part of many culinary preparations and is part of the Mediterranean diet where it plays a very important role due to the already known benefits of garlic.



GARLICGarlic is a source particularly rich in organosulfur compounds, which are responsible for its flavour, aroma, and potential health benefits, the different types of garlic supplements that are commercially available as garlic powders (tablets), garlic oils (capsules), and aged garlic extracts (tablets, capsules, and liquid) provide a different profile of organosulfur compounds [9,10].

Aged garlic extract (AGE), which is formed during garlic ageing (up to 20 months) as a result from the prolonged extraction of fresh garlic at room temperature, is an odourless garlic preparation containing S-allylcysteine (SAC) as its most abundant compound [10].

Several studies performed on one of its most abundant organosulfur compounds, S-allylcysteine (SAC) [10], showed how this active constituent may be the reason on the antioxidant properties of garlic and one of the benefits of garlic.

Additionally, we can mention that S-allylcysteine (SAC) is 30 times less toxic than other typical garlic compounds such as allicin and diallyldisulfide, it is easily absorbed in the gastrointestinal tract and can be detected in several tissues up to 8 hours after dosage [10]. Image: Garlic Mark by RBerteig under Creative Common license (CC BY 2.0).

Several reports have shown that aged garlic extract (AGE) and S-allylcysteine (SAC), inhibit the oxidative damage implicated in ageing and a variety of diseases [10], what we all know as oxidation, a process that natural antioxidants as garlic are able to fight. Different antioxidant mechanisms have been attributed to these compounds and confirmed.



GARLICQuorum sensing, also known as bacterial intracellular communication, is the mechanism by which cells are able to control basic cellular activities and coordinate their actions [13], and the way bacteria are able to infect our bodies in a coordinated and structured way.

Quorum sensing is, in other words, the mechanism used by bacteria to synchronize their behaviour, including the virulence of their attacks, antibiotic resistance, bio-film formation (communities of micro-organisms attached to a surface [14])...etc., and all this in order to react appropriately to external signal and manage their primary goal, a bacterial infection.

Breaking bacterial intracellular communication is a way to stop bacterial infections on a natural way that scientists and pharmaceutical companies have investigated since recent years to fight multi-drug resistance of bacteria. Image: Garlic by Will Merydith under Creative Common license (CC BY-SA 2.0).

Where traditional antibiotics failed to treat infections caused by bacterial bio-films and multi-resistant bacteria as gram-negative bacteria, quorum sensing inhibitors managed to stop an infection, something especially interesting in gram-negative bacteria, shielded in a protective film and immune to most known antibiotics and for which quorum sensing seems to be the last line of defence.

Garlic (Allium sativum), extract show certain antibiotic properties against Pseudomonas aeruginosa [15,16] and other studies performed on garlic extracts have revealed that the derivatives responsible for quorum sensing inhibitory activity include ajoene, as well as sulfides and polysulfides. 



Another common misconception is that garlic is an effective mosquito repellent. In spite the benefits of garlic are many being a mosquito repellent is not one of them. Garlic does have a moderate repellent effect when rubbed on the skin [26,27], although there are far more effective repellents available that also have a more pleasing odour.

Additionally, the consumption of garlic has not been shown to be effective at repelling mosquitoes either [26].



Periodontitis is a set of inflammatory diseases affecting the periodontium, i.e., the tissues that surround and support the teeth, affecting millions of patients every year against which garlic has demonstrated to be very effective.

Even the Porphyromonas gingivalis bacteria, a pathogen associated with chronic periodontitis, can be fought by garlic, in spite of lower sensitivity to it when compared to the previous groups of oral pathogens[17].

Garlic extract is also effective against Streptococcus mutans both in vitro and in vivo [18], and it is believed that it might be used as an effective remedy for the prevention of dental caries.



The regular intake of garlic has been demonstrated to have a beneficial cardiovascular effect, being able to reduce blood pressure and improving cardiovascular abnormalities [20.21], being this one of the benefits of garlic that has been most references in medical libraries.

Two garlic active constituents responsible for these cardioprotective properties seem to be allicin and alliin, compounds that have been shown to possess cardioprotective properties [22,23].

Garlic flesh extract is known to have very high amounts of allicin and alliin when compared with the garlic skin extract, which suggests that those two constituents, in spite playing an important role on the cardioprotective properties of garlic, may not be the primary ones [24].



In our article about Mediterranean diet herbs, we already mentioned these incredible antimicrobial properties of Garlic, the strongest among all the different Mediterranean diet herbs, but we didn't directly mentioned its potential use for the treatment and prevention of dental caries, let's hope this article can clarify how Garlic achieves this function and why it's so important to include it in our diets.



Many are indeed the benefits of garlic, in spite the most known refer to the anti-microbial properties, probably exerted by garlic due to its high content of allicin, one of its most powerful and therapeutic active constituents found in garlic and effective for the treatment of many groups of bacteria, as:

  • Streptococcus mutans,
  • Streptococcus sobrinus,
  • Aggregatibacter actinomycetemcomitans,
  • Fusobacterium nucleatum and
  • actinomyces oris among many others [1]



Additionally, other garlic extract properties that are worth being mentioned include its proven efficiency in the treatment of the paediatric tumour neuroblastoma [19], something that will certainly encourage scientists and pharmaceutical companies to keep on studying the many active constituents that this wonderful herb has.



Complementary and alternative medicine has always been used to treat human affections and illnesses, especially by those ethnics groups using herbs and herbal remedies as an integral part of their culture, but... Is there any relationship between those treatments and the survival rate? and if so, which herbs and herbal remedies are the most commonly used by breast cancer survivors?

Disclaimer: The information presented on this website is not intended to prescribe or give in any way or form medical advice, recommend or diagnose. Please read the disclaimer at the bottom of this page for more info.



[1] Preventing the common cold with a garlic supplement: a double-blind, placebo-controlled survey. Josling P. Garlic Centre, Battle, East Sussex, United Kingdom.
[2] Selenium deficiency increases the pathology of an influenza virus infection1 MELINDA A. BECK,*,†,2 HEATHER K. NELSON,* QING SHI,† PETER VAN DAEL,‡ EDUARDO J. SCHIFFRIN,‡ STEPHANIE BLUM,‡ DENIS BARCLAY,‡ AND ORVILLE A. LEVANDER§ Departments of *Nutrition and †Pediatrics, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-7220, USA; ‡Nestle´ Research Center, Lausanne, Switzerland; and §USDA, ARS, Beltsville Human Nutrition Research Center, Beltsville, Maryland, USA
[3] Antioxidant effects and antimicrobial activites of phytoncide. Abe T, Hisama M, Tanimoto S, Shibayama H, Mihara Y, Nomura M. TOYO BEAUTY CO., LTD, Higashinakamoto, Higashinari-ku, Osaka 537-0021, Japan.
[4] The phytoncide activity of several varieties of garlic stored for different periods of time. Borukh IF, Kirbaba VI, Barabash OIu, Demkevich LI.
[5] Toplak GK. Zagreb: Mozaik Kniga; 2005. Domace lekovito bilje; pp. 50–51.
[6] Extracts from the history and medical properties of garlic Biljana Bauer Petrovska and Svetlana Cekovska1
[7] Anti-Atherosclerotic Therapy Based on Botanicals. Orekhov AN, Sobenin IA, Korneev NV, Kirichenko TV, Myasoedova VA, Melnichenko AA, Balcells M, Edelman ER, Bobryshev YV. Source Dr. Yuri V Bobryshev, Faculty of Medicine, SOMS, University of New South Wales, Sydney NSW 2052, Australia.
[8] Garlic, by the University of Maryland Medical Center.
[9] Complementary and Alternative Medicine Use among Breast Cancer Survivors: The Black Women's Health Study.Bright-Gbebry M, Makambi KH, Phillips Rohan J, Llanos AA, Rosenberg L, Palmer JR, Adams-Campbell LL.
[10] The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection Ana L. Colín-González, 1 Ricardo A. Santana, 1 Carlos A. Silva-Islas, 1 Maria E. Chánez-Cárdenas, 1 Abel Santamaría, 2 and Perla D. Maldonado 1 ,*
[11] Reuter HD, Koch HP, Lawson LD. Therapeutic effects of garlic and its preparations. In: Koch HP, Lawson LD, editors. Garlic: The Science and Therapeutic Application of Allium Sativum L and Related Species. London, UK: Williams & Wilkins; 1996. pp. 13–162.
[12] Composition, stability, and bioavailability of garlic products used in a clinical trial. Lawson LD, Gardner CD J Agric Food Chem. 2005 Aug 10; 53(16):6254-61.
[13] Wikipedia (http://en.wikipedia.org/wiki/Cell_signaling)
[14] Biofilm formation as microbial development. O'Toole G, Kaplan HB, Kolter R. Department of Microbiology, Dartmouth Medical School, Hanover, New Hampshire 03755, USA.
[15] Inhibition of bacterial quorum sensing by vanilla extract. Choo JH, Rukayadi Y, Hwang JK. Department of Biotechnology, Yonsei University, Seoul, Republic of Korea.
[16] Screening for quorum-sensing inhibitors (QSI) by use of a novel genetic system, the QSI selector. Rasmussen TB, Bjarnsholt T, Skindersoe ME, Hentzer M, Kristoffersen P, Köte M, Nielsen J, Eberl L, Givskov M. Center for Biomedical Microbiology, BioCentrum-DTU, Technical University of Denmark, DK-2800 Kgs. Lyngby, Denmark.
[17] Garlic Allicin as a Potential Agent for Controlling Oral Pathogens. Bachrach G, Jamil A, Naor R, Tal G, Ludmer Z, Steinberg D. Institute of Dental Sciences, The Hebrew University-Hadassah School of Dental Medicine , Jerusalem, Israel
[18] Inhibitory activity of garlic (Allium sativum) extract on multidrug-resistant Streptococcus mutans. Fani MM, Kohanteb J, Dayaghi M. Department of Oral Medicine, School of Dentistry, Shiraz Medical School, Shiraz University of Medical Sciences, Shiraz, Iran
[19] Molecular Mechanisms of Anti-cancer Action of Garlic Compounds in Neuroblastoma. Karmakar S, Choudhury SR, Banik NL, Ray SK. Department of Pathology, Microbiology, and Immunology, University of South Carolina School of Medicine, Columbia, South Carolina, USA [20] Review Garlic and cardiovascular disease: a critical review. Rahman K, Lowe GM J Nutr. 2006 Mar; 136(3 Suppl):736S-740S.
[21] Review Effect of garlic on blood pressure: a systematic review and meta-analysis. Ried K, Frank OR, Stocks NP, Fakler P, Sullivan T
[22] BMC Cardiovasc Disord. 2008 Jun 16; 8():13. Allicin protects against cardiac hypertrophy and fibrosis via attenuating reactive oxygen species-dependent signaling pathways. Liu C, Cao F, Tang QZ, Yan L, Dong YG, Zhu LH, Wang L, Bian ZY, Li H J Nutr Biochem. 2010 Dec; 21(12):1238-50.
[23] Allicin in garlic protects against coronary endothelial dysfunction and right heart hypertrophy in pulmonary hypertensive rats. Sun X, Ku DD
[24] Am J Physiol Heart Circ Physiol. 2006 Nov; 291(5):H2431-8. Garlic extracts prevent oxidative stress, hypertrophy and apoptosis in cardiomyocytes: a role for nitric oxide and hydrogen sulfide Xavier Lieben Louis,1,2,3 Ryan Murphy,4 Sijo Joseph Thandapilly,1,2,3 Liping Yu,1,3 and Thomas Netticadan.
[25] Wikipedia article on Periodontitis under the Creative Commons Attribution-ShareAlike License.
[26] Plant-based insect repellents: a review of their efficacy, development and testing Marta Ferreira Maia1,2 and Sarah J Moore
[27] Greenstock DL, Larrea Q. Book Garlic as an insecticide. City: Doubleday Research Association; 1972. Garlic as an insecticide; p. 12. pp. 12.