A recent report suggests that eating garlic - either raw or as a supplement - does not lower cholesterol levels. However, some studies in 2006-2007 showed positive results, what could be the cause for the mixed results among the studies?
Mahmoodi M. and his co-workers from Rafsanjan, Iran, found that oral consumption of 5 g of garlic twice a day for 42 days was associated with lowered triglyceride and the total cholesterol levels.
Japanese researchers from Wakunaga Pharmaceutical Co., Ltd developed a monascus garlic fermented extract. They found that intake of this garlic extract for 2-4 weeks could reduce serum total cholesterol (TC) and low-density lipoprotein cholesterol levels significantly.
While, Russian researchers demonstrated that allicor (a long-acting garlic product) reduced total cholesterol and LDL cholesterol in 167 patients with hyperlipidemia.
How does garlic extract reduce cholesterol levels?
Garlic extracts reduce cholesterol synthesis by up to 75% without significant cellular toxicity. Diallyl disulfide, diallyl trisulfide, and allyl mercaptan are the key compounds for the inhibitory activities.
Why are there mixed results?
Rahman K and Lowe GM. at Liverpool John Moores University, UK, point out that epidemiologic studies show an inverse correlation between garlic consumption and progression of cardiovascular disease. Numerous in vitro and animal studies have confirmed the ability of garlic to reduce these parameters and suggested its mechanism on cholesterol-lowering activities.
The mixed results can simply be explained by different contents of the garlic extracts, preparations or experimental design in the studies. Note that the dose in Mahmoodi's study is 5 g of garlic twice a day for 42 days (positive results) while Zhang L used only 200 mg aged garlic extract and 1 mg steam-distilled garlic oil in his study (negative results).
