The Science of Garlic : Garlic Derivative, Ajoene, Inhibits Platelet Deposition

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The Science of Garlic : Garlic Derivative, Ajoene, Inhibits Platelet Deposition

JoAnn Guest Jan 11, 2005 19:29 PST

Heart Disease - The Science of Garlic

By Decker Weiss: NMD, AACVPR

 

http://heartspring.net/heart_disease_prevention.html

 

Today, garlic is one of the most researched plant medicines. By 1996,

more than 1,800 scientific studies had investigated garlic’s medicinal

properties.2 Through these studies, garlic has been verified as an

important natural supplement in the treatment of many health problems.

 

Why is garlic so beneficial?

Garlic chemistry is very complex. It’s rich in many active components,

including 75 different sulfur compounds. Allicin, the substance that

gives garlic its characteristic odor (and to those who partake of its

goodness —garlic breath) is the compound that’s most prized. Most garlic

producers strive to grow garlic plants with a high allicin yield.3

Without allicin, garlic might not have any benefit at all.

 

However, as important as allicin is to garlic growers and harvesters

alike, the concentration of allicin in an intact clove of garlic is

astonishingly small. This is because allicin is protected in the clove

by cell walls. It is only after the cell walls are crushed or cut that

garlic cloves release their allicin.3

 

While allicin itself has beneficial health effects, its greatest

strength is in what it yields. Once allicin is released, many compounds

are formed. These compounds are responsible for most of garlic’s health

benefits. 4 Allicin itself is highly unstable. In fact, allicin cannot

be detected in the bloodstream or urine at any time after eating

garlic.5

 

Allicin is also destroyed by stomach acid. Many commercial garlic

products are enteric-coated. The tablets go through the stomach intact

without dissolving. This delivers the garlic tablet to the small

intestine, where the tablet dissolves and releases its allicin. From the

small intestine, allicin’s many compounds are formed and then enter the

bloodstream. This form of supplementation also avoids the development of

garlic breath.5

 

Is it true that garlic is good for the heart?

Garlic has many beneficial properties that improve the health of the

heart and circulation. These include:

 

antioxidant activity6

anti-clotting agent7,8

inhibition of atherosclerosis (hardening of the arteries)9

 

reducing “bad” cholesterol levels in the blood10

raising “good” cholesterol levels in the blood11

lowering blood pressure

 

Recently, there have been some reports in the news that discount

garlic’s ability to lower cholesterol. Why is there such a difference in

garlic research results?

 

Prior to 1995, studies consistently concluded garlic lowered cholesterol

levels. However, since 1995, many clinical trials have concluded garlic

has no effect in lowering cholesterol levels in the blood. Researchers,

concerned about these findings decided to determine why this occurred.

 

The researchers, under the direction of Dr. Larry D. Lawson, examined

the garlic supplements used in the studies that found no beneficial

effect. One such study published in The Journal of the American Medical

Association in 1998, concluded that garlic had no effect on serum

cholesterol.

 

While allicin cannot be detected in blood or urine, it can be detected

in the breath.

 

Using the exact products previously studied (same lot numbers and year

of manufacture), Dr. Lawson measured the JAMA study’s test product, a

garlic oil.

 

When Dr. Lawson tested study subject’s breath after taking the garlic

oil, minimal allicin was detected.

 

However, when Dr. Lawson encapsulated the same oil in gelatin capsules

and had study subjects swallow the capsules, the same oil produced three

times as much allicin.

 

A recent meta-analysis (a large review study of several other studies

with statistical analysis) of clinical trials concluded the use of

garlic to lower cholesterol was, at best, of questionable value. Most of

the studies published after 1995 that concluded garlic had no effect on

serum cholesterol used non-enteric-coated tablets.15

 

Dr. Lawson studied the tablets used in these trials and determined the

tablets dissolved in the stomach. The allicin was released too early,

was destroyed by stomach acid, and never reached the bloodstream. 5

 

Dr. Lawson concluded the trials used poor-quality products. He further

concluded that when enteric coated tablets are manufactured using garlic

containing high allicin potential, serum cholesterol lowering effect

should be noted. He urged new clinical trials with such supplements.5

 

There has also been some controversy comparing the effectiveness of

supplements made with fresh garlic and those made from aged garlic

extract. Is there any way to determine which type of garlic supplement

is the most effective?

Some manufacturers of garlic supplements believe allicin is not the

effective compound in garlic. These companies manufacture aged-garlic

extract (AGE) products. They have initiated, funded, and conducted many

studies regarding the safety of garlic juice, garlic powder, and

enteric-coated garlic tablets. The studies have compared these products

to their AGE products. The studies frequently conclude fresh garlic and

enteric-coated garlic are harmful to stomach lining and can cause

ulcers.16,17 However, recently at the American Herbal Products

Association’s International Garlic Symposium, several noted garlic

researchers and experts disagreed with these findings. During a

roundtable discussion, the consensus determined there have been no

successful independent replications of the AGE studies. Furthermore, the

roundtable concluded that several ethnic groups consume large amounts of

raw garlic every day without any associated ill effects. There has never

been a clinically noted association of garlic consumption and ulcer

formation. And, finally, the scientists questioned the validity of the

study results due to sponsor-associated bias.18

 

What evidence is there for the anticancer benefits of garlic?

Much research has examined garlic’s role in the inhibition and

prevention of various types of cancer. Some of these studies have

evolved from the observations that certain ethnic groups who eat a lot

of garlic in their diet have a low incidence of certain types of

cancers.19

 

In a recent meta-analysis, the authors concluded garlic was especially

effective in preventing stomach and colon cancers.20-22

 

Are there any other scientifically documented health benefits to garlic?

 

Garlic is a powerful detoxifying agent that can protect against various

liver toxins. In an experimental study, garlic protected against

acetaminophen (Tylenol®)-induced liver toxicity.23 This means that

individuals who are taking Tylenol® may find garlic is beneficial.

Garlic can also kill harmful bacteria, fungi, and viruses.24-26

 

Is there a recommended daily dosage for allicin?

Based on a great deal of clinical research, a medically validated

commercial garlic product should provide a daily dose of a total allicin

potential of 4,000 micrograms (mcg). This dosage equates to roughly one

to four cloves of fresh garlic.19 Be sure to read labels; demand

products that deliver a guaranteed yield of allicin and are

enteric-coated to prevent premature release in the stomach.

 

Conclusion

Garlic is indeed a unique plant. It has a long and colorful history as

both food and medicine, and is highly valued as both. Scientific study

has provided understanding of the many benefits of garlic as a

supplement. And, most importantly, many loyal enthusiasts worldwide

attest to healthier hearts and improved lives simply from using garlic

supplements.

 

[Top]

 

References

1. Riddle JM. Garlic’s history as a medicine. Presentation at the

American Herbal Products Association International Garlic Symposium.

July 31, 2001.

 

2. Garlic. In: Blumenthal M, ed. Herbal Medicine: Expanded Commission E

Monographs. Austin, Tex: American Botanical Council; 2000:139-148.

 

3. Ellmore GS, Milano E, Feldberg RS. Navigating the clove: mapping

bioactive compounds in garlic (Allium sativum). Presentation at the

American Herbal Products Association International Garlic Symposium.

July 31, 2001.

 

4. Robbers JE, Tyler VE. Garlic. In: Tyler’s Herbs of Choice. New York,

NY: The Haworth Herbal Press; 1999:132-137

 

5. Lawson LD, Wang ZJ, Papadimitrou D. Allicin release under simulated

gastrointestinal condition for garlic powder tablets employed in

clinical trials on serum cholesterol. Planta Med. 2001;67:13-18.

 

6. Ho SE, Ide N, Lau BH. S-allyl cysteine reduces oxidant load in cells

involved in the atherogenic process. Phytomedicine. 2001;8:39-46.

 

7. Ali M, Thomson M. Consumption of a garlic clove a day could be

beneficial in preventing thrombosis. Prostaglandins Leukot Essent Fatty

Acids. 1995;53:211-212.

 

8. Gadkari JV, Joshi VD. Effect of ingestion of raw garlic on serum

cholesterol level, clotting time and fibrinolytic activity in normal

subjects. J Postgrad Med. 1991;37:128-131.

 

9. Orekhov AN, Grunwald J. Effects of garlic on atherosclerosis.

Nutrition. 1997;13:656-663.

 

10. Silagy C, Neil garlic as a lipid lowering agent—a meta-analysis. J R

Coll Physicians Lond. 1994;28:39-45.

 

11. Morcos NC. Modulation of lipid profile by fish oil and garlic

combination. J Natl Med Assoc. 1997;89:673-678.

 

12. Al-Qattan KK, Khan I, Alnaqeeg MA, Ali M. Thromboxane-B2,

prostaglandin-E2 and hypertension in the rat 2-kidney 1-clip model: a

possible mechanism of the garlic induced hypotension. Prostaglandins

Leukot Essent Fatty Acids. 2001;64:5-10.

 

13. Qidwai W, Qureshi R, Hasan SN, Azam SL. Effect of dietary garlic

(Allium Sativum) on the blood pressure in humans-a pilot study. J Pak

Med Assoc. 2000;50:204-207.

 

14. Berthold HK, Sudhop T, von Bergmann K. Effect of a garlic oil

preparation on serum lipoproteins and cholesterol metabolism: a

randomized controlled trial. JAM 1998;279:1900-1902.

 

15. Stevinson C, Pittler MH, Ernst E. Garlic for treating

hypercholesteremia: a meta-analysis of randomized clinical trials. Ann

Intern Med. 2000;133:420-429.

 

16. Sumiyoshi H. New pharmacological activities of garlic and its

constituents. Nippon Yakurigaku Zasshi. 1997;1:93-97.

 

17. Kasuga S, Uda N, Kyo E, Ushijima M, Morihara N, Itakura Y.

Pharmacologic activities of aged garlic extract in comparison with other

garlic preparations. J Nutr. 2001;131:1080-1084.

 

18. Amagase H, Block E, Bordia A, Lawson LD. The controversial issues

surrounding allicin versus non-allicin containing products. Presentation

at the American Herbal Products Association International Garlic

Symposium. Aug. 1, 2001.

 

19. Reuter HD, Koch HP, Lawson LD. Anticancer effects. In: Koch HP,

Lawson LD. Garlic: The Science and Therapeutic Application of Allium

sativum and Related Species. Baltimore, Md: Williams & Wilkins;

1998:176-187.

 

20. Fleischauer AT, Arab L. Garlic and cancer: a critical review of the

epidemiologic literature. J Nutr. 2001; 131:1032S-1041S.

 

21. Knowles LM, Milner J Possible mechanism by which allyl sulfides

suppress neoplastic cell proliferation. J Nutr. 2001;131:1061S-1066S.

 

22. Lamm DL, Riggs DR. Enhanced immunocompetence by garlic: role in

bladder cancer and other malignancies. J Nutr. 2001;131:1067S-1070S.

 

23. Hu JJ, Yoo JS, Lin M, Wang EJ, Yang CS. Protective effects of

diallyl sulfide on acetaminophen-induced toxicities. Food Chem Toxicol.

1996;34:963-969.

 

24. Guo NL, Lu DP, Woods GL, et al. Demonstration of the anti-viral

activity of garlic extract against human cytomegalovirus in vitro. Chin

Med J (Engl). 1993;106:93-96.

 

25. O’Gara EA, Hill DJ, Maslin DJ. Activities of garlic oil, garlic

powder, and their diallyl constituents against Helicobacter pylori. Appl

Environ Microbiol. 2000;66:2269-2273.

 

26. Ledezma E, Marcano K, Jorquera A, et al. Efficacy of ajone in the

treatment of tinea pedis: a double blind and comparative study with

terbinafine. J Am Acad Dermatol. 2000;43:829-832.

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