Garlic health benefit, research and side effects, use for immune system enhancement, blood pressure lowering benefits, heart disease, by Ray Sahelian, M.D.
February 24 2014

Garlic has been used medicinally since antiquity due of its ability to improve the immune system, fight germs of all sorts, and reduce the risk for heart disease disease. Garlic bulbs were found in tombs of the pharaohs, in Crete, and in ancient cultures throughout the world. Hippocrates considered it to be a vital part of his therapeutic armamentarium. Garlic is a member of the same group of plants as the onion.

Raw versus cooked
Raw garlic is more potent than cooked, because heat inactivates the enzyme allinase. Allinase gives garlic its odor and stimulates the formation of allicin, which may be the key to the health-enhancing properties of this bulb. Some of the potency of raw garlic may be reduced when garlic is cooked or processed and packaged in pill form. I prefer people consume raw garlic - since it is much more effective - rather than the pills, but the odor may be a deterrent and in that case the capsules are an option.

Garlic and Parsley supplement, Source Naturals
Source Naturals Garlic and Parsley oil contains true oils of garlic and parsley seed, extracted from whole fresh garlic bulb and parsley seed, and suspended in pure soy bean oil. It is a convenient way to receive the benefits in concentrated form, without the taste and odor.



 

 

Buy Garlic supplement or see a complete list of high quality products

Supplement Facts per 2 caps
Garlic Oil 5 g (equivalent to 500 mg of fresh garlic)
Parsley Seed Oil 200 mg (equivalent to 100 mg of fresh parsley)

Health benefits

A good antioxidant
Effects of garlic consumption on plasma and erythrocyte antioxidant parameters in elderly subjects.
Gerontology. 2008.
Subjects ingested garlic at the daily dose of 0.1 g/kg body weight for 1 month. Before and after this period, fasting blood samples were obtained, and oxidant [malondialdehyde (MDA) and xanthine oxidase] and antioxidant [superoxide dismutase, glutathione peroxidase and catalase] parameters were studied in erythrocytes. Our results show that ingestion of garlic leads to significantly lowered plasma and erythrocyte MDA levels and to increased activities of some antioxidant enzymes, which indicates that consumption of garlic decreases oxidation reactions.

Garlic and blood pressure - possible mechanism of action
Red blood cells process compounds from digested garlic and turn them into the cell messenger hydrogen sulfide (H2S) which relaxes blood vessels and increases blood flow.
Those who are already on blood pressure medications are not likely to have significant reduction when adding fresh garlic to their diet. However, if you have hypertension, do discuss with your doctor that you are planning to take garlic and initially use only a small clove once a day. Over time you can gradually increase the amount of garlic you use while you monitor your blood pressure. Hopefully it may be possible to reduce the dosage of BP medications, such as beta blockers and angiotensin converting enzyme inhibitors (captopril).

Pak J Pharm Sci. 2013 September. Effects of Allium sativum on systolic and diastolic blood pressure in patients with essential hypertension. The present study evaluated the effects of garlic on blood pressure in patients with essential hypertension. Patients (n=210) with stage 1 essential hypertension were divided into 7 groups named as A, B, C, D, E, F and G. Each group comprised of 30 patients. Each patient in group A, B, C, D and E has received garlic tablets at the dose of 300/mg. 600/mg, 900/mg, 1200/mg and 1500/mg in divided doses per day respectively for 24 weeks while Group F & group G were given tablet atenolol and placebo respectively. Blood pressure readings were recorded at weeks 0, 12 and 24. Present study showed significant decrease in both Systolic and Diastolic blood pressure in both dose and duration dependent manner. In each garlic treated group, significant reduction in SBP and DBP were observed when compared with atenolol and placebo.

Aged garlic extract lowers blood pressure in patients with treated but uncontrolled hypertension: a randomised controlled trial. Maturitas 2010.

Effects of Garlic on Blood Pressure in Patients With and Without Systolic Hypertension: A Meta-Analysis.
Ann Pharmacother. 2008.
We examined the effect of garlic on blood pressure in patients with and without elevated systolic blood pressure through meta-analyses of randomized controlled trials. A systematic search of MEDLINE, CINAHL, and the Cochrane Central Register of Controlled Trials was conducted to identify randomized controlled trials in humans evaluating garlic's effect on blood pressure. All databases were searched using the key words garlic, Allium sativum, and allicin. Ten trials were included in the analysis. Garlic reduced systolic blood pressure by 16 mm Hg and diastolic blood pressure by 9 mmHg compared with placebo in patients with elevated systolic blood pressure. However, the use of garlic did not reduce systolic blood pressure or diastolic blood pressure in patients without elevated blood pressure.

Dr. Karin Ried and colleagues from The University of Adelaide in South Australia included published studies in their meta analysis, identifying 11 studies in which patients were randomly assigned to garlic or placebo. In most studies, participants given garlic took it in powdered form, as a standardized supplement. Doses ranged from 600 mg to 900 mg daily, which study participants took for 12 to 23 weeks. When Dr. Karin Ried and her team pooled the data from the trials, they found that garlic reduced systolic blood pressure by 4 mm Hg, on average. An analysis limited to people with high blood pressure showed garlic reduced systolic blood pressure by 8 mm Hg, on average, and diastolic blood pressure by 7 mm Hg. The higher a person's blood pressure was at the beginning of the study, the more it was reduced by taking garlic. The 600 mg to 900 mg dosage used in the studies is equivalent to 3 mg to 5 mg of garlic's active ingredient, allicin. A fresh clove of garlic contains 5 mg to 9 mg of allicin. BMC Cardiovascular Disorders, published online June 16, 2008.

Dipak K. Das at the University of Connecticut School of Medicine in Farmington report that raw, crushed garlic generates hydrogen sulfide through a chemical reaction. Although best known as the stuff that gives rotten eggs their distinctive odor, hydrogen sulfide also acts as a chemical messenger in the body, relaxing blood vessels and allowing more blood to pass through. However, processed and cooked garlic are not as able to generate hydrogen sulfide. Dipak K Das gave freshly crushed garlic and processed garlic to two groups of lab rats, and then studied how well the animals' hearts recovered from simulated heart attacks. Both reduced damage from lack of oxygen, but the fresh garlic group had a significantly greater effect on restoring good blood flow in the aorta and increased pressure in the left ventricle of the heart, Journal of Agricultural and Food Chemistry, Aug 2009.

Blood thinner
Garlic has anti-platelet activity. Those who are on warfarin (Coumadin) should be cautious regarding the combination. Perhaps consuming garlic may reduce the required dosage of anti-coagulants.

Cancer
There is evidence that onions and garlic protect against tumor growth in humans. It has been suggested that this effect is partly due to the organosulfur compounds in allium vegetables and that these substances act through induction of phase II detoxification enzymes.
   Eating just one clove of raw or cooked garlic daily may help protect against stomach, esophageal, and colon cancer. That's the conclusion reached by a researcher at the University of North Carolina at Chapel Hill who analyzed 17 international population studies examining the eating habits of more than 100,000 people. 
   A review of several studies has found that older adults with the highest onion and garlic intakes had the lowest risks of a number of cancers -- including colon, gastrointestincal, ovarian and throat cancers. Garlic has a large number of potent bioactive compounds with anticancer properties, largely allylsulfide derivatives. Garlic derivatives influence a number of molecular mechanisms in carcinogenesis, including DNA adduct formation, scavenging of free radicals, mutagenesis, cell proliferation and differentiation, and angiogenesis. The growth rate of cancer cells is reduced by garlic, with cell cycle blockade that occurs particularly in the G2/M phase. Apoptosis is stimulated by garlic. Perhaps garlic may be beneficial in prostate cancer.
   Eat more of this spice to reduce the risk of breast cancer. Cancer Biol Ther. 2009 Nov; Garlic constituent diallyl trisulfide induced apoptosis in MCF7 human breast cancer cells.
   This bulb may be helpful against the skin cancer melanoma.

Cholesterol in the blood and influence on lipids
Nutr Rev. 2013. Effect of garlic on serum lipids: an updated meta-analysis. Discipline of General Practice, The University of Adelaide, Adelaide, South Australia, Australia; National Institute of Integrative Medicine, Melbourne, Victoria, Australia.
This meta-analysis, the most comprehensive to date, includes 39 primary trials of the effect of garlic preparations on total cholesterol, low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, and triglycerides. The findings suggest garlic to be effective in reducing total serum cholesterol by 17 ± 6 mg/dL and low-density lipoprotein cholesterol by 9 ± 6 mg/dL in individuals with elevated total cholesterol levels (>200 mg/dL), provided garlic is used for longer than 2 months. An 8% reduction in total serum cholesterol is of clinical relevance and is associated with a 38% reduction in risk of coronary events at 50 years of age. High-density lipoprotein cholesterol levels improved only slightly, and triglycerides were not influenced significantly.

Common cold
Elizabeth Lissiman of the University of Western Australia in Crawley reviewed the medical literature for trials comparing garlic to placebo, no treatment, or standard treatment, and found one study that met their quality criteria. In this study, 146 people were randomly assigned to take a supplement containing 180 milligrams of allicin (a component of garlic) or placebo once a day for 3 months. During that time, the garlic group reported 24 cases of the cold, compared to 65 in the placebo group. The garlic takers also were sicker for a shorter amount of time in total (111 days compared to 366), but took about the same amount of time to recover from their colds. People in the garlic group complained of rash and odor, but there were no serious side effects. Cochrane Database of Systematic Reviews 2009.

Supplementation with aged garlic extract improves both NK and γδ-T cell function and reduces the severity of cold and flu symptoms: A randomized, double-blind, placebo-controlled nutrition intervention. Clin Nutr. 2012.

Dental abscess and tooth infection, dental caries, toothache, tooth Infection, abscess remedy? Help for dental pain, a natural antibiotic?
Some people report improvement in their tooth infection after consuming several cloves of garlic a day or applying chopped garlic on or near the tooth for a few minutes every couple of hours. Hopefully this will reduce the problem or discomfort until you are evaluated by a dentist. Garlic has anti-microbial activity in the mouth. It can potentially reduce the risk of certain oral infections. Garlic may be helpful in reducing tooth plaque formation and tooth decay.

Garlic (allium sativum) extract has been known to have inhibitory activity on various pathogenic bacteria, viruses and fungi. The objective of present investigation was to study in vitro inhibitory activity of garlic extract on multidrug-resistant (MDR) strains of Streptococcus mutans isolated from human carious teeth. Of 105 carious teeth tested, 92 (87%) isolates of S. mutans were recovered, among which 28 (30%) were MDR since they were resistant to four or more antibiotics. The highest rate of resistance was observed for tetracycline and least resistance to teichoplanin and vancomycin while a quarter of the isolates were resistant to penicillin and amoxicillin. All isolates of S. mutans were sensitive to garlic extract. Considering in vitro data obtained in the present study, mouthwashes or toothpaste containing optimum concentration of garlic extract could be used for prevention of dental caries. Inhibitory activity of garlic extract on multidrug-resistant Streptococcus mutans. J Indian Soc Pedod Prev Dent. 2007.

The antimicrobial activity of two garlic clones' (1: purple and 2: white) crude extracts against oral microbiota was evaluated in vitro (study 1) and in vivo (study 2). Study 1 consisted of the evaluation of minimum inhibitory (MIC) and bactericidal (MBC) concentrations against nine streptococci strains. In study 2, a 2.5% garlic (clone 2) solution was used as a mouthwash in a 5-week study by 30 subjects. Blood agar and Mitis Salivarius Bacitracin agar were inoculated with subjects' saliva to quantify oral microorganisms and mutans streptococci. Study 2 showed that 2.5% garlic mouthwash solution had good antimicrobial activity against mutans streptococci and oral microorganisms. Maintenance of reduced salivary levels of streptococci was observed after 2 weeks at the end of mouthwash use. Unpleasant taste (100%), halitosis (90%) and nausea (30%) were reported by subjects after the end of the study. It was concluded that the garlic clones have antimicrobial properties in vitro against streptococci and anticariogenic properties against oral microorganism in spite of its adverse effects. Int J Dent Hyg. 2007. Antimicrobial activity of garlic against oral streptococci. Department of Physiological Sciences - Piracicaba Dental School, University of Campinas, Piracicaba, São Paulo, Brazil.

Antimicrobial activity of garlic, tea tree oil, and chlorhexidine against oral microorganisms.
Int Dent J. 2002.
To compare the antimicrobial activity of tea tree oil, garlic, and chlorhexidine solutions against oral microorganisms. The five-week study consisted of thirty subjects. The first week was considered baseline. All subjects used a control solution (second week), and were randomly divided into the three groups (third week): G1-0.12% chlorhexidine; G2 - 2.5% garlic (Allium sativum, L.); and G3 - 0.2% tea tree oil (Melaleuca alternifolia). Dishes containing blood agar and Mitis Salivarius Bacitracin agar (MSB) were inoculated with the subjects' saliva (collected twice a week). Total microorganisms and mutans streptococci were counted in blood agar and MSB, respectively. Chlorhexidine and garlic groups showed antimicrobial activity against mutans streptococci, but not against other oral microorganisms. The tea tree oil group showed antimicrobial activity against mutans streptococci and other oral microorganisms. Maintenance of reduced levels of microorganisms was observed only for garlic and tea tree oil during the two consecutive weeks (fourth and fifth). Unpleasant taste (chlorhexidine 40%, tea tree oil 30%, garlic 100%), burning sensation (chlorhexidine 40%, tea tree oil 60%, garlic 100%), bad breath (chlorhexidine 40%, tea tree oil 20%, garlic 90%), and nausea (chlorhexidine 0%, tea tree oil 10%, garlic 30%) were reported. Garlic and tea tree oil might be an alternative to chlorhexidine.

Erectile dysfunction, impotence
Excessive production of reactive oxygen species (ROS) by an overactive nicotinamide adenine dinucleotide phosphate (NADPH) oxidase system in penile tissue is an important mechanism of erectile dysfunction. S-allyl cysteine (SAC), a bioactive component derived from garlic, can restore erectile function in diabetic rats by preventing ROS formation through modulation of NADPH oxidase subunit expression. S-allyl cysteine restores erectile function through inhibition of reactive oxygen species generation in diabetic rats. Andrology. 2013.

Gallstones
Feeding garlic and onion effectively accelerates the regression of preformed cholesterol gallstone by promoting cholesterol desaturation in bile.

Heart disease prevention
Consumption lowers the risk of atherosclerosis (hardening of the arteries). Garlic is beneficial to the heart and blood vessels, but freshly crushed garlic has more potent heart-healthy benefits. Investigators at the University of Connecticut School of Medicine in Farmington also challenge the widespread belief that most of garlic's benefits are due to its rich content of antioxidants. Dipak K. Das and colleagues point out that raw, crushed garlic generates hydrogen sulfide through a chemical reaction. Although best known as the stuff that gives rotten eggs their distinctive odor, hydrogen sulfide also acts as a chemical messenger in the body, relaxing blood vessels and allowing more blood to pass through. However, processed and cooked garlic loses its ability to generate hydrogen sulfide. Dipak K Das gave freshly crushed garlic and processed garlic to two groups of lab rats, and then studied how well the animals' hearts recovered from simulated heart attacks. Both crushed and processed garlic reduced damage from lack of oxygen, but the fresh garlic group had a significantly greater effect on restoring good blood flow in the aorta and increased pressure in the left ventricle of the heart, Journal of Agricultural and Food Chemistry, Aug 2009.

This herb reduces  the risk for heart and blood pressure disease by stimulation of nitric oxide generation in endothelial cells which leads to improved blood flow and by the generation of hydrogen sulfide (H2S) which relaxes vascular smooth muscle, induces vasodilation of blood vessels, and significantly reduces blood pressure.

Immune system, antibacterial, antifungal, activity against against bacterial, viral, mycotic and parasitic infections
This bulb has potent activity against certain bacteria and parasites. Garlic can combat intestinal parasites, perhaps fungal infections such as athlete's foot, and perhaps vaginal yeast infections. Could it be helpful in reducing or preventing traveler's diarrhea? 

May be effective against tapeworm infections
Streptolysin O is a potent cytolytic toxin produced by almost all strains of group A streptococci and is considered an important virulence factor for this organism. Allicin likely inhibits the Streptolysin O by binding to the cysteine residue in the binding site. Allicin may be a potential alternative drug against streptococcal diseases. J Med Microbiol. 2010; Inhibition of streptolysin O by allicin - an active component of garlic.

Oral administration of crude garlic ameliorates the adverse impacts of hepatic coccidiosis on rabbits when used as a prophylactic, but garlic was less effective as a therapeutic. Trop Anim Health Prod. 2010. Garlic and hepatic coccidiosis: prophylaxis or treatment?

Pseudomonas aeruginosa is an opportunistic pathogen that colonizes urinary catheters, forms biofilms, and is responsible for causing persistent and recurrent nosocomial catheter-associated urinary tract infections (UTIs). Our results suggest that decreased virulence of P. aeruginosa in garlic-fed mice can be attributed to the quorum-sensing inhibitory property of garlic. This might have contributed towards reduced production of virulence factors, as seen in vitro. FEMS Immunol Med Microbiol. 2010 March. Garlic blocks quorum sensing and attenuates the virulence of Pseudomonas aeruginosa.

It is a promising therapeutic agent for schistosomiasis mansoni infection. Trop Biomed. 2009 Apr; Effects of garlic on albino mice experimentally infected with Schistosoma mansoni: A parasitological and ultrastructural study.

Eur J Obstet Gynecol Reprod Biol. 2009 Sep; Long-term symptomatic group B streptococcal vulvovaginitis: eight cases resolved with freshly cut garlic.

Zhongguo Ji Sheng Chong Xue Yu Ji Sheng Chong Bing Za Zhi. 2012. Killing effect of garlic extract on Schistosoma japonicum cercariae and Oncomelania snails.

Garlic has a wide range of antibacterial, antiviral, antifungal and antiprotozoal activity. Additional microbes whose growth may be inhibited:
Aspergillus - Lett Appl Microbiol. 1995; Antifungal effects of Allium sativum (garlic) extract against the Aspergillus species involved in otomycosis.
Candida species
Enterococcus faecalis
Escherichia coli
Helicobacter pylori stomach infection
Neisseria gonorrhoeae
Salmonella species
Staphylococcus aureus and methicillin-resistant S. aureus MRSA
Staphylococcus epidermidis
Streptococcus pneumoniae,
Streptococcus pyogenes
Haemophilus influenzae
Salmonella typhi
Proteus species
Shigella species

Insecticide and pesticide exposure protection
Compounds in this plant can reduce damage from certain insecticides and pesticides. Food Chem Toxicol. 2010 August. Protective Effects of Garlic Extract and Vitamin C Against In vivo Cypermethrin-Induced Teratogenic Effects in Rat Offspring.

Prostatitis
It could be some benefit as a adjunct to treatment for prostatitis.

Pulmonary hypertension
An ingredient in garlic appears to prevent a potentially deadly type of high blood pressure affecting the lungs, at least in rats. The garlic ingredient, called allicin, seems to ward off pulmonary hypertension, or high blood pressure in the arteries that bring blood to the lungs. In humans, pulmonary hypertension can lead to potentially fatal complications in the heart and blood vessels. Humans would need to eat two cloves of garlic every day to equal the rats' dose of allicin.

Toxicity for medications
May be useful in gentamicin toxicity.

Garlic extract, tablets, capsules and various forms
Garlic pills are sold in various extracts, including aged and extract with 2% allicin. I prefer to eat a fresh clove rather than to take a supplement, but each person has a different preference. Each garlic clove weighs about 2 to 5 grams. Odorless pills are available. Heated, cooked, or roasted garlic is less healthy. Garlic bread is not a good way to get the benefit since there is little actual garlic and much of the ingestion is white bread with no nutritional value.

Garlic side effects or caution, safety, caution, danger
It may be a good idea to not consume high doses if you plan to have surgery because of the possible blood thinning properties of garlic. Very high intake of garlic may cause easy bruising.

Chemistry and how it works
Garlic has been shown to metabolized into N-aceryl-S-allyl cysteine, allyl mercaptan, diallyl disulfide, diallyl sulfide, diallyl sulfoxide, diallyl sulfone, and allyl methyl sulfide. Garlic has been thought to bring about its anticarcinogenic effect through a number of mechanisms, such as the scavenging of radicals as an antioxidant, increasing gluathione levels, increasing the activities of enzymes such as glutathione S-transferase, catalase, inhibition of cytochrome p4502E1, DNA repair mechanisms, prevention of chromosomal damage etc. Sulfur compounds, including allicin, appear to be the active components in the root bulb of the garlic plant.

Garlic breath reduction, how to minimize the odor
Garlic odor or breath is caused by conversion of alliin to volatile sulfur compounds. Consider the use of mint, parsley, or fennel seeds to partially counteract this bad breath. Drinking whole milk may also help. Keep in mind that garlic breath can last more than 24 hours.

Effect of milk on the deodorization of malodorous breath after garlic ingestion.
Food Sci. 2010.
The effect of milk and milk components on the deodorization of diallyl disulfide (DADS), allyl methyl disulfide (AMDS), allyl mercaptan, allyl methyl sulfide, and methyl mercaptan in the headspace of garlic as well as in the mouth- and nose-space after garlic ingestion was investigated. Fat-free and whole milk significantly reduced the head-, mouth-, and nose-space concentrations of all volatiles. Water was the major component in milk responsible for the deodorization of volatiles. Due to its higher fat content, whole milk was more effective than fat-free milk in the deodorization of the more hydrophobic volatiles diallyl disulfide and allyl methyl disulfide. Milk was more effective than water and 10% sodium caseinate in the deodorization of allyl methyl sulfide, a persistent garlic odor, in the mouth after garlic ingestion. Addition of milk to garlic before ingestion had a higher deodorizing effect on the volatiles in the mouth than drinking milk after consuming garlic. Practical Application: Ingesting beverages or foods with high water and/or fat content such as milk may help reduce the malodorous odor in breath after garlic ingestion and mask the garlic flavor during eating. To enhance the deodorizing effect, deodorant foods should be mixed with garlic before ingestion.

Garlic and cholesterol, lipid levels, no major benefit seen yet
Three forms of garlic -- including raw garlic and two types of commercial garlic supplements -- did not significantly reduce LDL cholesterol during a six-month trial. .

The efficacy of cholesterol-lowering action and side effects of garlic enteric coated tablets in man.
J Med Assoc Thai. 2004.
The present study aimed at investigating the cholesterol-lowering and side effects of garlic enteric coated tablets in comparison with placebo tablets. The study is a randomized double-blinded crossover design involving 116 volunteers. However, 16 of them did not complete the study. The remaining 100 volunteers were divided into two groups: 45 were in the trial group and the remaining 55 in the control group. The volunteers in the trial group were asked to take garlic tablets in the first three months, placebo in the second three months and discontinue all tablets in the last three months, while the volunteers in the control group started with three months of placebo followed by three months of garlic tablets and ended up with three months of tablets discontinuity. The results showed that there were no significant differences in the total serum cholesterol levels between the two groups at the end of three months or six months of the study. Side effects included headache, itching and complaints of garlic smell. No serious side effects relating to liver, kidney functions or hematologic side effects were detected.

Effect of garlic (Allium sativum) powder tablets on serum lipids, blood pressure and arterial stiffness in normo-lipidaemic volunteers: a randomised, double-blind, placebo-controlled trial.
Br J Nutr. 2004.
We tested the effect of dried garlic powder on blood lipids, blood pressure and arterial stiffness in a 12-week randomised, double-blind, placebo-controlled trial. Seventy-five healthy, normo-lipidaemic volunteers (men and women aged 40-60 years) were assigned to dried garlic powder tablets (10.8 mg alliin (3-(2-propenylsulfinyl)-L-alanine)/d, corresponding to about three garlic cloves) or placebo. Sixty-two subjects were eligible for the per-protocol analysis. The primary outcome measure was serum total cholesterol concentration. Secondary outcome measures were LDL-cholesterol, HDL-cholesterol and triacylglycerol concentrations, blood pressure and arterial stiffness (assessed by pulse wave velocity). No significant differences between the garlic and placebo groups were detected for any of the outcome measures. However, garlic powder was associated with a near-significant decrease (12 %) in triacylglycerol concentration. In conclusion, garlic powder tablets have no clinically relevant lipid-lowering and blood pressure-lowering effects in middle-aged, normo-lipidaemic individuals. The putative anti-atherosclerotic effect of garlic may be linked to risk markers other than blood lipids.

Garlic allergy
I see many advertisements about immune system and garlic. I have discovered that I am allergic to garlic and byproducts. Is there any research on the subject of garlic allergy?
   Diallyl disulphide is the major allergen in garlic and onion. Garlic use may cause allergic reactions (allergic contact dermatitis, generalized urticaria, angiedema, pemphigus, anaphylaxis and photoallergy), alteration of platelet function and coagulation (with a possible risk of bleeding). Contact dermatitis, particularly affecting the fingertips, can be caused by garlic allergy.

Research
Comparison of the Bioactive Compounds and Antioxidant Potentials of Fresh and Cooked Polish, Ukrainian, and Israeli Garlic.
J Agric Food Chem. 2005.
Garlic is an essential part of Polish, Ukrainian, and Israeli cuisine. The aim of this investigation was to compare the changes in bioactive compounds, proteins, and antioxidant potentials in fresh Polish, Ukrainian, and Israeli garlic samples after subjection to cooking temperature. Dietary fiber and essential trace elements were comparable. Polyphenols, tocopherols, proteins, and antioxidant potentials were higher in Polish garlic, but not significantly. The SDS- and native-PAGE electrophoretic patterns of all three fresh garlic samples were without significant differences. Most of the proteins were in the molecular mass range of 24-97 kDa, and the more intensive major bands were concentrated at 50 and 12 kDa. The 50 kDa protein nearly disappears and the intensity of the 12 kDa lectin bands slightly decreases during cooking. It was observed that the bioactive compounds, antioxidant potential, and proteins in garlic decrease significantly after 20 min of cooking at 100 degrees C. In conclusion, (a) the bioactive compounds, electrophoretic patterns, and antioxidant potential of fresh Polish, Ukrainian, and Israeli garlic samples are comparable; (b) garlic samples subjected to 100 degrees C during 20 min preserve their bioactive compounds, antioxidant potential, and protein profile and are comparable with fresh garlic; and (c) fresh garlic should be added to dishes cooked at 100 degrees C in the last 20 min of the cooking process.

Garlic has been used as an herbal medicine, but there is no report on the health benefits of the skin or peel. The extract of garlic skins (peels) showed strong antioxidant activity, and some responsible constituents were isolated and identified. These compounds were phenylpropanoids, N-trans-Coumaroyloctopamine, N-trans-feruloyloctopamine, guaiacylglycerol-beta-ferulic acid ether, and guaiacylglycerol-beta-caffeic acid ether were identified as were trans-coumaric acid and trans-ferulic acid.

Emails
I suspect you've all been asked this question many times before, but I thought I'd ask if you can briefly tell us if you believe that garlic provides the health benefits so often claimed for them. If you believe it provides any or all of these benefits, are you also of the opinion that these benefits are nullified if people ingest garlic supplements for instance from a product made by
Source Naturals or if the pills are not "enteric coated?"
   I do think garlic, just like onions, is very valuable and should definitely be part one's diet. Each vegetable or spice has a role to play in health and a wide variety is crucial. I prefer eating fresh garlic as opposed to pills or capsules but many people have to interact with others on a close and daily basis and having the bad breath is not an option. I have not seen any studies regarding enteric coated... my instincts tell me that enteric coated is not necessary.

I took fresh garlic, liquified it with a little water, filtered it and applied the solution to my scrotum. The juice can burn a little so sometimes I have to add a little water to my balls-o-fire. I let it dry for an hour then rinse it off. It really makes me feel horny, brings on spontaneous erections, prolongs my erection and improves control. I have been doing this once a week and it really seems to be effective. What is your opinion of this and do you think there is anything in garlic that can do some damage? What do you think it contains that makes it work so well? If you try it, I'm sure you will add it to your list.
   Congratulations on exploring a novel and quite creative approach to sexual enhancement. You certainly have balls! I can't see any harm from this approach, and perhaps I will ask a friend who has an interest in this approach to give it a try. This approach, using garlic on testicles, is certainly novel thinking outside the box.

Does a garlic supplement interfere with 5-HTP nutrient, curcumin supplement, ahcc, or the herb saw palmetto?
   Garlic has a mild effect and should not interact with any great degree with curcumin or any of these supplements.

I came across a site this morning that claims garlic can elevate testosterone levels, Since I have a history of low testosterone and currently have levels which are low/normal naturally I am interested in this claim. I visited your site immediately to see what information you had on garlic, but discovered there was no information regarding the role of garlic on testosterone levels. So I ask: is there anything to this claim on garlic raising testosterone levels. Thanks for a great site and your time.
   Although there have been a few studies with garlic feeding in rodents that have shown conflicting results regarding testosterone levels, no such human studies could be found as of April 2010. Rodent studies regarding garlic supplementation are not reliable in terms of extrapolating to humans since, when animal studies are done, a very high amount of garlic is fed to them as opposed to humans who only eat at most a few cloves a day. Therefore, at this time, I see no evidence that eating small amounts of garlic will have any appreciable influence on testosterone levels in humans.

Can one swallow the whole clove and get the same benefits as when you crush it? Will it be absorbed into the body if swallowed whole?
   Probably, especially if the clove is small, the intestinal tract will likely dissolve it and digest it.

I have been taking garlic tablets for a long time but it seems to have stopped working as my blood pressure goes up and down and my sugar level now is staying higher then normal thy have tasted my kidney, So could it be possible that the garlic tablets are not working on my body anymore I'm 68 and on a lot of medication.
   The influence of garlic tablets on blood pressure is minimal, perhaps 2 to 8 points maximum, and blood pressure fluctuates throughout the day sometimes by significant amounts. Various medications can sometimes influence blood pressure.

It is known that vasodilators such as nitrates combined with sildenafil citrate can cause severe hypotension, resulting to heart failure and death. It is also known that garlic also dilates blood vessels. Can a combination of garlic capsules used as a preventive measure for arterial cholesterol buildup and sildenafil citrate; or even the consumption of a clove of garlic per day and sildenafil citrate can cause a dangerous state of hypotension due to garlic's vasodilation effect? Let me specify, that we are talking about normal quantities or amounts of garlic used along with acceptable mg of sildenafil citrate (25 to 50 mg before intercourse) taken by healthy adults without prior health problems or using other medications.
   I seriously doubt there would be any untoward reactions or side effects with the combination of sildenafil and garlic. The influence of garlic herb on vasodilation is minimal compared to the effects of sildenafil.

Can Nattokinase be taken with garlic capsules?
    It is not possible to give an answer that applies to everyone. Much depends on the dosage of each and other supplements and medications that are being used, the person's diet, overall health status, their genetic blood clotting abilities, etc. As a general rule, nattokinase is a potent blood thinner while garlic is a mild blood thinner.

I am a 44 year old male with diabetes, hypertension, depression, high cholesterol and over 100 pounds overweight. I purchased Nature Bounty garlic 2000 mg to help with some of these conditions. What dosage is recommended in your research to help with my situation. Is the tablet form of garlic good to take or should i use another form.
    The ideal form of garlic is raw, but capsules or tablets are acceptable, too. I cannot say what amount you should take but garlic is a healthy supplement to use.