Overview
Garlic (大蒜精) has long been consumed by human worldwide. Only modern studies have revealed its many health benefits including the maintenance of cardiovascular and heart health and the reduction of cholesterol levels.† However, you may not know that garlic's benefits are most lost in our normal way of preparation. Only the specially made garlic extract can give all the health benefits.

Garlic Health Benefits
Many clinical trials have been conducted by researchers in USA and Europe to evaluate the medicinal use of garlic such as in cholesterol control. In a meta analysis of garlic clinical trials, for treating hypercholesterolemia, 13 randomized, placebo-controlled, and double-blind trials were identified. The analysis revealed that all but three trials showed that garlic is significantly superior to placebo in the reduction of total cholesterol levels. When all trials are pooled together, a significant reduction in total cholesterol levels is found in patients taking garlic. The level of reduction in total cholesterol is on average at 15.7 mg/dL (200 mg/dL is the point considered to be high cholesterol). The same analysis does not find garlic makes any significant reduction in low-density lipoprotein (LDL, bad) cholesterol levels and any significant increase in high-density lipoprotein (HDL, good) cholesterol levels.¹

The total cholesterol reduction by garlic is modest compared to the cholesterol drugs like lipitor. However, the mild action, the safety (see below), and the very low cost of garlic extracts as a dietary supplement make it ideal for people to consume daily to maintain healthy levels of cholesterol.

Active Ingredients
Research on garlic showed the garlic ingredients responsible for its health benefits are allicin. However, allicin is found only in very small amounts in fresh garlic cloves. When garlic is crushed in food preparation and exposed to water, much more allicin is produced by an enzyme in garlic that converts alliin to allicin and gives the odor. Allicin is unfortunately very short lived and quickly degraded. Therefore, normal garlic preparation does not retain the allicin activity.

Garlic fresh bulb can be made to dry powder and tablets without converting alliin to allicin by special processes. The tablets can be further enteric coated so that alliin will only be converted to allicin in the intestines but not in the mouth, which ensures that allicin is produced where it is absorbed and functional and that no odor will occur in the mouth.

Such garlic extracts are what researchers have used in the garlic clinical trials. The standard garlic extracts are about 3 times concentrated from fresh cloves and the potential to generate allicin vary but most commonly is at 1%.

Dose and Duration
In the garlic clinical trials, patients took 540 mg to 1340 mg standardized extract per day. Such doses are expected to yield 4 mg to 10 mg allicin. The most common dose is 800 mg or 900 mg. Any garlic takeup with less than 4 mg allicin production is considered not sufficient. The trials commonly last for 3 to 6 months.

Garlic Side Effects
Side effects are few in the garlic clinical trials and do not occur more often in people taking garlic than taking placebo. ¹ However, mild gastrointestinal symptoms were occasionally observed.

Garlic Drug Interaction
There are reports suggesting that garlic may interact with other prescription drugs such as blood thinner warfarin, anti-HIV drug saquinavir. So caution needs to be taken if you are on other medications.

Reference
1. Stevinson C, Pittler MH, Ernst E. Garlic for treating hypercholesterolemia. A meta-analysis of randomized clinical trials. Ann Intern Med. 2000 Sep 19;133(6):420-9.

by X. Li, Ph. D. (credential)