Garlic

Garlic is probably the best researched and most commonly used herb in the world. Native to Central Asia, garlic is now used in most every country’s cuisine. Mention of garlic can be found in the ancient medical texts of Egypt, India, China, Greece, and Rome, some dating as far back as 5,000 years. This world-renowned cure-all herb has been touted for everything from weight loss and infections to low energy, dysentery, snake bites and low libido.[1] A search through the research literature of today yields over 4,000 citations on garlic, suggesting it is just as popular in modern times as it was in ancient times.

Much of the research on garlic has focused on the organosulfur compounds, or OSCs, found in the whole clove, which are responsible for its flavor and distinct smell. While allicin is probably the best recognized of the OSCs, there are actually many different types of OSCs found in garlic. Some of these compounds, like allicin are dependent on enzymes that are activated when garlic is crushed, chopped, or chewed. Others, like those found in aged garlic supplements, are formed in a water solution instead.[2] These OSCs are believed to be responsible for most of the health benefits of garlic, the best known of which are as a cardiovascular tonic, a microbe fighter, an immune supporter and an inflammation modulator.

Cardiovascular Benefits

Garlic has long been used for conditions that affect the cardiovascular system. As far back as 3,000 BCE garlic was believed to strengthen the heart and keep the blood fluid;[3] how it does this is currently being investigated. Garlic has been shown to support healthy blood pressure levels[4] by inhibiting the aggregation of platelets, thus keeping the blood flowing smoothly,[5] and by relaxing the blood vessels.[6] Garlic may also benefit the cardiovascular system by supporting healthy cholesterol levels and modulating inflammation.[7] Research into garlic’s role in cardiovascular health continues to grow, and many animal and in vitro (test tube) studies look promising, but controlled human trials have yielded some conflicting results.[8] More research is still needed before we will understand exactly how garlic supports the cardiovascular system.

Infections

As far back as 1858, Louis Pasteur carried out experiments to confirm the historically recognized bacteria-fighting activity of garlic.[9] Today garlic is recognized for its ability to fight not only bacteria, but also fungi, viruses and parasites.[10] Consumed regularly, garlic may help to reduce the occurrence of the common cold in adults.[11] Besides fighting microbes directly, garlic may serve as a prebiotic, helping to strengthen the good intestinal bacteria so they are better able to fight off infectious agents in the first place.[12]  Garlic also reduces the inflammatory compounds that certain microbes produce.[13]

Cancer

Researchers around the world have noticed a connection between diets high in garlic and lower rates of certain types of cancers. Although much more research is needed to fully understand this connection, the OSCs in garlic are believed to support many protective bodily functions. First, OSCs support the detoxification process, helping the body to neutralize and eliminate carcinogens. OSCs also appear to prevent carcinogenic compounds from binding to and damaging DNA and may play a role in initiating apoptosis, or programmed cell death, of tumor cells.[14],[15] While cancer is a complex multifactorial disease, it is possible that garlic can help the body protect itself from tumor formation.

Other Benefits

Several of the OSCs found in garlic have been investigated for their ability to modulate inflammation.[16],[17] While reduction of inflammation may have broad-reaching effects throughout the body, research has revealed possible benefits specifically in reducing the brain inflammation associated with the development of neurodegenerative conditions, such as Alzheimer’s disease.[18],[19] Garlic may also have antioxidant capabilities, although its effects on free radical damage need further clarification.[20] Finally, garlic is often recommended to support healthy detoxification, as it helps to cleanse the blood and aids liver function.[21],[22]

Perhaps nowhere is the line between food and medicine so blurred as it is with garlic. It may be tempting to rely solely on fresh garlic for its many benefits, but the amount needed to reverse an already established condition may be beyond the amount that could be comfortably consumed from food alone. In these cases, a garlic supplement is probably a better choice. However, as a preventative, the food form is a great option, and it is likely that other beneficial compounds in the diet may react synergistically with those in garlic to produce an even greater effect.[23]


References

[1] Brown DJ. Herbal Prescriptions for Health & Healing. Twin Lakes, WI: Lotus Press;2000.

[2] Drake VJ. Garlic and organosulfur compounds. Linus Pauling Institute Oregon State University. http://lpi.oregonstate.edu/infocenter/phytochemicals/garlic/ July 2008. Accessed May 28, 2013.

[3] Aggarwal BB. Healing Spices. New York, NY: Sterling Publishing; 2011.

[4] Ried K, Frank OR, Stocks NP. Aged garlic extract lowers blood pressure in patients with treated but uncontrolled hypertension: A randomized controlled trial. Maturitas. 2010; 67(2): 144-150.

[5] Allison GL, Lowe GM, Rahman K. Aged garlic inhibits platelet activation by increasing intracellular cAMP and reducing the interaction of GPIIb/IIIa receptor with fibrinogen. Life Sci. 2012; 91(25-26):1275-80.

[6] Benavides GA, Squadrito GL, Mills RW, Patel HD, Isbell TS, Patel RP, et al. Hydrogen sulfide mediates the vasoactivity of garlic. Proc Natl Acad Sci USA. 2007; 104(46)):17977-82.

[7] Drake VJ. Garlic and organosulfur compounds. Linus Pauling Institute Oregon State University. http://lpi.oregonstate.edu/infocenter/phytochemicals/garlic/ July 2008. Accessed May 28, 2013.

[8] Zeng T, Zhang CL, Zhao XL, Xie KQ. The roles of garlic on the lipid parameters: a systemic review of the literature. Crit Rev Food Sci Nutr. 2013; 53(3):215-30.

[9] Brown DJ. Herbal Prescriptions for Health & Healing. Twin Lakes, WI: Lotus Press;2000.

[10] Ankri S, Mirelman D. Antimicrobial properties of allicin from garlic. Microbes Infect. 1999; 1(2):125-129.

[11] Fashner J, Ericson K, Werner S. Treatment of the common cold in children and adults. Am Fam Physicians. 2012; 86(2):153-9.

[12] Wood R. The New Whole Foods Encyclopedia. New York, NY: Penguin Compass; 1999.

[13] Keiss HP, Dirsch VM, Hartung T, Haffner T, Trueman L, Auger J, et al. Garlic (Allium sativum L.) modulates cytokine expression in lipopolysaccharide-activated human blood thereby inhibiting NF-kappaB activity.  J Nutr. 2003; 133(7):2171-5.

[14] Bianchini F, Vainio H. Allium vegetables and organosulfur compounds: do they help prevent cancer? Environ Health Perspect. 2001; 109(9):893-902.

[15] Iciek M, Dwiecien I, Wlodek L. Biological properties of garlic and garlic-derived organosulfur compounds. Environmental and Molecular Mutagenesis. 2009; 50(3):247-265.

[16] Lee da Y, Li H, Lim HJ, Jeon R, Ryu JH. Anti-inflammatory activity of sulfur-containing compounds from garlic. J Med Food. 2012;15(11);992-9.

[17] Chang HP, Huang SY, Chen YH. Modulation of cytokine secretion by garlic oil derivatives is associated with suppressed nitric oxide production in stimulated macrophages. J Agric Food Chem. 2005; 53(7):2530-4.

[18] Lin GH, Lee YJ, Choi DY, Han SB, Jung JK, Hwang BY, et al. Anti-amyloidogenic effect of thiacremonone through anti-inflammation in vitro and in vivo models. J Alzheimers Dis. 2012;29(3):659-76.

[19] Ashafag M, Khan MM, Shadab Raza S, Kuwaja G, Javed H, et al. S-allyl cysteine mitigates oxidative damage and improves neurologic deficit in a rat model of focal cerebral ischemia. Nutr Res. 2012;32(2):133-43.

[20] Banerjee SK, Mukherjee PK, Maulik SK. Garlic as an antioxidant: the good, the bad and the ugly. Phytother Res. 2003;17(2):97-106.

[21] Oliver S. The Detox Manual. Orem, UT: Woodland Publishing; 2004.

[22] Gittleman AL. The Fat Flush Plan. New York, NY: McGraw-Hill; 2002.

[23] Givskov M. Beyond nutrition: health-promoting foods by quorum-sensing inhibition. Future Microbiology. 2012; 7(9):1025-1028.

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