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Garlic

Garlic for Flavor─ Not Lowering Cholesterol

  • Large segments of population believe in and utilize herbal products and garlic is an important component in complementary and alternative medicine.
  • The various health claims of the benefits of garlic include lowering cholesterol, blood pressure, homocysteine, antioxidant properties, as well as preventing heart disease, heart attack, and diabetes. 1-3
  • Effectiveness of garlic in cardiovascular disease (CVD) was more encouraging in experimental studies, which prompted several clinical trials. While a few small earlier studies showed beneficial effects of garlic, more recent large studies failed to confirm the earlier findings. 
  • Several reviews have critically examined current scientific literature concerning claims of cardiovascular benefits from regular consumption of garlic or garlic preparations. 4-7 The vast majority of recent randomized, placebo-controlled studies do not support a role for garlic in lowering blood lipids.5, 8
  • A rigorous trial with constant assessment of chemicals in the study material in 192 patients found that over a 6-month follow-up, raw garlic and 2 commercial preparations do not significantly affect lipid levels. It is unlikely that garlic is useful in preventing CVD.8
  • The available evidence from randomized controlled trial does not demonstrate any beneficial effects of garlic on serum cholesterol and its use to lower cholesterol is of questionable value at best.9, 10
  •  Although two meta-analyses suggested slight lowering of blood pressure with garlic it cannot be recommended for lowering blood pressure in people with high blood pressure.5, 11, 12
  • Investigation of antithrombotic (blood thinning) effects of garlic consumption appears to hold promise, but too few data exist to draw firm conclusions.5
  • Possible explanations for the contradictory results include publication bias, overestimation of treatment effects in trials with inadequate concealment of treatment allocation, or if the constituent trials are small.13
  • There has been no trial to show that garlic reduces clinical CVD outcomes such as heart attack or stroke.

Sources

1. Yeh YY, Yeh SM. Homocysteine-lowering action is another potential cardiovascular protective factor of aged garlic extract. J Nutr. Mar 2006;136(3 Suppl):745S-749S.

2. Ginter E, Simko V. Garlic (Allium sativum L.) and cardiovascular diseases. Bratisl Lek Listy. 2010;111(8):452-456.

3. Luis DA, Aller R. [Garlic and cardiovascular risk]. An Med Interna. May 2008;25(5):237-240.

4. Banerjee SK, Maulik SK. Effect of garlic on cardiovascular disorders: a review. Nutr J. Nov 19 2002;1:4.

5. Brace LD. Cardiovascular benefits of garlic (Allium sativum L). J Cardiovasc Nurs. Jul 2002;16(4):33-49.

6. Rahman K, Lowe GM. Garlic and cardiovascular disease: a critical review. J Nutr. Mar 2006;136(3 Suppl):736S-740S.

7. Reinhart KM, Talati R, White CM, Coleman CI. The impact of garlic on lipid parameters: a systematic review and meta-analysis. Nutr Res Rev. Jun 2009;22(1):39-48.

8. Ong HT, Cheah JS. Statin alternatives or just placebo: an objective review of omega-3, red yeast rice and garlic in cardiovascular therapeutics. Chin Med J (Engl). Aug 20 2008;121(16):1588-1594.

9. Khoo YS, Aziz Z. Garlic supplementation and serum cholesterol: a meta-analysis. J Clin Pharm Ther. Apr 2009;34(2):133-145.

10. Stevinson C, Pittler MH, Ernst E. Garlic for treating hypercholesterolemia. A meta-analysis of randomized clinical trials. Ann Intern Med. Sep 19 2000;133(6):420-429.

11. Ried K, Frank OR, Stocks NP, Fakler P, Sullivan T. Effect of garlic on blood pressure: a systematic review and meta-analysis. BMC Cardiovasc Disord. 2008;8:13.

12. Reinhart KM, Coleman CI, Teevan C, Vachhani P, White CM. Effects of garlic on blood pressure in patients with and without systolic hypertension: a meta-analysis. Ann Pharmacother. Dec 2008;42(12):1766-1771.

13. Neil HA, Silagy CA, Lancaster T, et al. Garlic powder in the treatment of moderate hyperlipidaemia: a controlled trial and meta-analysis. J R Coll Physicians Lond. Jul-Aug 1996;30(4):329-334.

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