INTRODUCTION
Garlic is the edible bulb from a plant in the lily family. Garlic, onions, leeks, scallions, shallots and chives are classified as members of the Allium genus. Thus, they are commonly described as Allium vegetables. Its nutrition facts of 1 tsp (2.8 g) of garlic are as follows: 0 g of total fat, 0 mg of cholesterol, 0 mg of sodium, 11 mg of potassium, 0.9 g of total carbohydrate. (Google, Nov., 2014)
Garlic is thought, in particular, to be linked to various beneficial health effects, from reducing blood pressure and cholesterol to treating cancer. Garlic may also prossess of antifungal, antibacterial, cardio-protective, antioxidant and anti-cancer activities. In cancer studies, a host of studies provide compelling evidence that garlic and its organic allyl sulfur components are effective inhibitors of the cancer process. Several its ingredients are involved in garlic's possible health benefits of anticancer activities. Garlic contains allyl sulfur and other compounds that slow or prevent the growth of tumor cells. [1] Further, because it is a source of potassium, it may benefit certain users at risk of hypertension. However, garlic side effects can be serious including skin irritation and swelling of legs. The main ingredient in garlic was already known and called allicin.
GARLIC HEALTH BENEFITS ON SERVERAL CONDITIONS
DIABETES Researchers from Alexandria University, Egypt administrated alloxan as a single dose (120mg/kgBW) to induce diabetes in rats. They fed the rats with a dose of 1ml of either onion or garlic juices/100g body weight (equivalent to 0.4g/100gBW) daily to for four weeks. They found that the glucose, urea, creatinine and bilirubin levels significantly increased in the plasma of diabetic rats. They also found that aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and alkaline and acid phosphatases (AlP, AcP) activities significantly increased in plasma and testes of alloxan-diabetic rats. They concluded that garlic and onion juices exerted antioxidant and antihyperglycemic effects and consequently may alleviate liver and renal damage caused by alloxan-induced diabetes [1A]
ATHEROSCLEROSIS Ide N and colleagues from Loma Linda University, USA, confirmed the antioxidant effects of fructosyl arginine (Fru-Arg), a MRP from aged garlic extract in vitro study. They further suggested to use Fru-Arg for the prevention of atherosclerosis and other related disorders. [2A] However, Santo SM et al from Gaubius Laboratory, The Netherlands didn't observe any protective benefits of garlic powder printanor on atherosclerosis in a 28 week study of APOE*3-Leiden transgenic mouse; based on atherosclerotic lesion type, area or composition. They also reported that garlic powder printanor did not display any benefits of hypolipidemic, anti-inflammatory or anti-atherosclerotic activities. [3A] The conflicting results indicate the importance of the dosage form preparation and experimental design.
TRIACYLGLYCEROL LEVEL Turner B and colleagues from Dansk Droge, Ishoj, Denmark also found that there was no significant differences between the garlic and placebo groups in term of total serum cholesterol concentration, LDL-cholesterol, HDL-cholesterol and triacylglycerol concentrations, blood pressure and arterial stiffnessin a 12-week randomised, double-blind, placebo-controlled trial. But, they found that garlic powder was associated with a 12% decrease in triacylglycerol concentration. I[6A]
HIGH BLOOD PRESSURE Garlic's key ingredient-allicin may prevent primary pulmonary hypertension (a form of high blood pressure) from a study in rats. [4A]
CANCERS A host of studies provide compelling evidence that garlic and its organic allyl sulfur components are effective inhibitors of the cancer process. These studies reveal that the benefits of garlic are not limited to a specific species, to a particular tissue, or to a specific carcinogen. Of 37 observational studies in humans using garlic and related allyl sulfur components, 28 studies showed some cancer preventive effect. The evidence is particularly strong for a link between garlic and prevention of prostate and stomach cancers. However, more clinical studies are needed to confirm these findings. [1-6]
Several compounds are involved in garlic's possible anticancer effects. Garlic contains allyl sulfur and other compounds that slow or prevent the growth of tumor cells. Allyl sulfur compounds, which occur naturally in garlic and onions, make cells vulnerable to the stress created by products of cell division. Because cancer cells divide very quickly, they generate more stressors than most normal cells. Thus, cancer cells are damaged by the presence of allyl sufur compounds to a much greater extent than normal cells. [1-6]
MICROBES Can garlic kill germs? Fuselli SR et al from Universidad Nacional de Mar del Plata, Funes, Argentina have different opinion after they finished their study on the microbial growth of garlic during storage. They found that Penicillium spp., Monilia spp., Lactobacillus brevis, Leuconosto mesenteroides subsp. mesenteroides and yeasts grow from garlic. And they found penicillium spp., Monilia spp., Lactobacillus brevis and yeasts from dry garlic. [7A]
GARLIC PREPERATION Vs HEALTH BENEFITS
The chemistry of garlic is complicated. As a result, the quality of garlic products depends on the manufacturing process. Peeling garlic and processing garlic into oil or powder can increase the number and variety of active compounds. Peeling garlic releases an enzyme called allinase and starts a series of chemical reactions that produce diallyl disulfide (DADS). DADS is also formed when raw garlic is cut or crushed. However, if garlic is cooked immediately after peeling, the allinase is inactivated and the cancer-fighting benefit of DADS is lost. Scientists recommend waiting 15 minutes between peeling and cooking garlic to allow the allinase reaction to occur. [1-6]
Researchers from Thailand also found that there were no significant differences in the total serum cholesterol levels between the group dosed with garlic tablet (enteric-coated) and that dosed with placebo tablet. [5A] This may be also an indication of the importance of the dosage form preparation and study design.
GARLIC SIDE EFFECTS
Although health benefits of garlic are frequently reported, excessive intake can have harmful effects. In a rat study, allicin, the main pungent ingredient in garlic, was found to be an activator of TRPA1. The neurons released neurotransmitters in the spinal cord to generate pain signals and released neuropeptides at the site of sensory nerve activation, resulting in vasodilation as well as inflammation. [2] Other garlic side effects include headache, itching garlic odor on breath and skin, occasional allergic reactions, stomach disorders and diarrhea, decrease in serum protein and calcium levels, association with bronchial asthma, contact dermatitis and complaints of garlic smell [5A]
Garlic preparations vary in concentration and in the number of active compounds they contain. Thus, quality control is an important consideration when foods such as garlic are considered for use as a cancer-fighting agent.
REFERENCES
(1) Amagase, H., Petesch, B.L., Matsuura, H. et al. (2001) "Intake of garlic and its bioactive components." J. Nutr. 131: 955S-926S. (2) Fleischauer, A.T. and Arab, L. (2001) "Garlic and cancer: a critical review of the epidemiologic literature." J. Nutrition 131: 1032S-1040S. (3) Milner, J.A. (2001) "Mechanisms by which garlic and allyl sulfur compounds suppress carcinogen bioactivation. Garlic and carcinogenesis." Adv. Exp. Med. Biol 492: 69-81. (4) Milner, J.A. (2001) "A historical perspective on garlic and cancer." J. Nutrition 131: 1027S-1031S. (5) "Allium Vegetables and Organosulfur Compounds: Do They Help Prevent Cancer?" http://ehpnet1.niehs.nih.gov/members/2001/109p893-902bianchini/bianchini-full.html. (6) "Garlic: Effects on Cardiovascular Risks and Disease, Proliferative Effects Against Cancer, and Clinical Adverse Effects." http://ahrq.gov/clinic/epcsums/garlicsum.htm.
1 Curr Opin Lipidol. 1994 Feb;5(1):6-10 2. Macpherson IJ. The pungency of garlic: activation of TRPA1 and TRPV1 in response to allicin. Curr Biol. 2005 May 24;15(10)929-34. [1A] Food Chem Toxicol. 2005 Jan;43(1):57-63].[2A] J Nutr Biochem. 1999 Jun; 10 (6):372-6].[3A]Atherosclerosis. 2004 Dec;177(2):291-7].[4A] Garlic Boosts Lung Health in Rats, HealthDay, April 3, 2005[5A] J Med Assoc Thai. 2004 Oct; 87 (10):1156-61].[6A] Br J Nutr. 2004 Oct; 92 (4):701-6].[7A] Rev Argent Microbiol. 2004 Jul-Sep; 36 (3):139-44].