For thousands of years, humans have prized garlic for its culinary, medicinal and magical qualities. Garlic is a member of the Alliaceae family that includes onions, shallots, leeks and chives. Garlic is antibacterial, antiviral and anti-fungal and may prevent some forms of cancer, lower serum cholesterol, thin the blood, lower blood pressure and help the body regulate blood sugar.
Garlic and Blood Pressure
In the June 2008 issue of "BMC Cardiovascular Disorders," researchers at the University of Adelaide analyzed the data from previous research on the effect of garlic on blood pressure. Their analysis showed an average reduction of systolic blood pressure of 4.6 mm mercury compared to placebo. In patients diagnosed with hypertension, systolic pressure was reduced by 8.4 mm mercury while the diastolic pressure fell by 7.3 mm mercury.
How It Works
Researchers at the University of Alabama at Birmingham published a study in the "Proceedings of the National Academy of Science, USA," that documented the way the body converts the sulfur containing compounds in garlic into hydrogen sulfide. Hydrogen sulfide is a potent vasodilator. The sulfur compounds in garlic give the herb its distinctive odor and taste. Hydrogen sulfide's ability to dilate blood vessels lowers blood pressure and protects the heart.
In addition, garlic may also lower blood pressure by decreasing sodium levels in the body. In a study published in the October 2003 issue of "Prostaglandins Leukotrienes and Essential Fatty Acids," researchers at Kuwait University found that the rate of sodium re-uptake in rats decreased significantly when the rats were given garlic. It is believed that compounds in garlic blocked the action of the kidneys' sodium ion pump.
Comparision of Garlic Formulations
Garlic supplements differ widely in tolerability, potency and cost. Raw garlic is prepared for supplemental use in one of four ways: steam-distillation. expressed essential oil, crushed garlic cloves mixed with oil, dried and ground into powder and alcohol extracts. A garlic supplement's potency is determined by the amount of the compound allicin it contains. Allicin and its derivatives are what gives garlic its smell, taste and health benefits.
Raw garlic may be eaten to lower blood pressure. Whole cloves of garlic do not contain allicin but a precursor called allin instead. An enzyme present in fresh garlic cloves is released when the clove is sliced diced or crushed. This enzyme, allinase, converts allin to active allicin. Powdered garlic also contains very little allicin. The labeling on most powdered garlic tablets state how much allicin each dose may yield, rather than how much each dose actually contains.
Dosage
The World Heath Organization recommends a daily dose of 2 to 5 g of fresh garlic. A clove of fresh garlic is about 3 g. This is equivilant to 0.4 to 1.2 g of dried powder, 2 to 5 mg of oil, and 300 to 1,000 mg of dried extract. Look to achieve an allicin yield of 2 to 5 mg. For fresh garlic, chop the cloves up finely and let them sit for about 30 minutes. This waiting period allows allicinase to convert allin to allicin. Garlic cooked immediately after it is chopped contains very little allicin.
Drug Interactions and Side Effects
The FDA considers garlic supplements to be safe, but side effects include bad breath, stomach upset, allergic reactions, body odor, heartburn or nausea. Garlic can interfere with the blood clotting process, causing complications in patients taking anticoagulant drugs such as coumadin or during surgery. Garlic can also add to the antiplatelet effect of dipyridamole, clopidogrel or aspirin.
Conclusion
Garlic supplements are a safe, effective and natural way for patients with hypertension to lower their blood pressure. United States Pharmacopeia standardized, enteric-coated, dried garlic powder tablets are relatively inexpensive, well tolerated and yield high levels of allicin.
References
- Linus Pauling Institute Micronutrient Information Center: Garlic and Organosulfur Compounds
- BioMed Central: Effect of garlic on blood pressure: A systematic review and meta-analysis
- Pubmed Central: Hydrogen sulfide mediates the vasoactivity of garlic
- ScienceDirect Abstract: Mechanism of garlic (Allium sativum) induced reduction of hypertension in 2K-1C rats: a possible mediation of Na/H exchanger isoform-1
- World Health Organization: WHO Monographs on Selected Medicinal Plants Volume One
