Heating Garlic Can Reduce Some of Its Biological Activity

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Heating Garlic Can Reduce Some of Its Biological Activity

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Heating Garlic Can Reduce Some of Its Biological Activity

 

http://www.herbalgram.org/herbalgram/articleview.asp?a=2349

 

HerbalGram. 2002;56:20 © American Botanical Council (Buy This Issue)

 

 

Research Reviews

 

Heating Garlic Can Reduce Some of Its Biological Activity

 

Reviewed: Song K, Milner JA. The influence of heating on the anticancer

properties of garlic. American Society for Nutritional Sciences. 2001

[supplement]:1054S-1057S.

 

The potential medicinal value of garlic (Allium sativum L., Alliaceae or

Liliaceae) has been recognized for thousands of years. The authors cite

studies that have shown that garlic has a variety of pharmacologic

properties, including hypolipidemic (blood lipid-lowering), hypoglycemic

(blood glucose-lowering), antibacterial, antifungal, antioxidant, and

anticancer effects.

 

Support for the anticancer effect of garlic has come from epidemiologic,

animal, and laboratory studies. Preclinical research has shown that

garlic can protect a number of body tissues against different kinds of

carcinogens and can interfere with cancer development at both the

initiation and promotion stages. This article reviews research about the

effects of heating garlic on its anticancer potential. " Although the

minimum daily intake required to reduce cancer risk remains to be

determined, garlic has been categorized as a dietary anticarcinogen, "

the authors write.

 

Laboratory research suggests that the anticancer substances in garlic

include both lipid-soluble and water-soluble sulfur compounds. Garlic is

distinguished from many other vegetables because of its high sulfur

content, and it is thought that the many allyl sulfur compounds in

garlic, including S-allylcysteine (SAC), a water-soluble

sulfur-containing amino acid, probably explain many of its medicinal

properties.

 

According to the authors' own research, microwave heating for as little

as 30 seconds blocked 90 percent of the activity of alliinase, the

enzyme that is activated when garlic is crushed or cut. Alliinase

rapidly converts alliin to allicin. Allicin is responsible for garlic's

odor, and is considered one of the most important biologically active

compounds found in crushed garlic. Microwave heating of garlic for 60

seconds destroyed all alliinase activity. When alliinase is inactivated

by heat, alliicin and its derivities cannot be formed. The authors cite

studies showing that boiling garlic at 100 degrees C for 20 minutes

inactivated its cardiovascular benefits, antifungal effects, antioxidant

properties, and ability to inhibit cyclooxygenase (an enzyme that plays

a role in the development of some types of cancer).

 

The authors also performed a study to measure the effects of heating

garlic (dosage information was not included in the report) upon a rat

anticancer assay. Raw garlic was effective in reducing formation of DNA

adducts by 64 percent, and garlic that had been microwaved for 30

seconds provided a similar degree of protection. However, microwaving

garlic for 60 seconds destroyed all of its anticancer benefits, whether

the garlic had been crushed before heating or not. Letting crushed

garlic sit at room temperature for 10 minutes before microwave heating

preserved 70 percent of its anticarcinogenic effects, compared with the

effects of raw garlic. Cutting the top off of whole, intact garlic and

letting it sit for 10 minutes before oven heating also preserved some of

its anticancer effects, whereas oven heating for 45 minutes without

cutting the top of the garlic destroyed all of its anticarcinogenic

potential.

 

Thus, this research suggests that many of the medicinal effects of

garlic are reduced or destroyed by heating. Inactivation of alliinase

and other heat-sensitive materials in garlic is probably the mechanism

by which heating has this negative effect. " Although garlic is known for

its many pharmaceutical effects, these abilities can be depressed by

preparation or processing methods, " the authors conclude.

 

--Christina Chase, M.S., R.D.

 

 

 

 

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