Roles of garlic and its bioactive compounds in modulating cholesterol metabolism

Hypercholesterolemia is one of the risk factors causing atherosclerotic cardiovascular diseases. Nutraceuticals and phytochemicals have garnered attention for their potential to lower plasma cholesterol with fewer side effects. Among these, garlic has been shown to be one of the most effective nutraceuticals for lowering plasma cholesterol.

Most in vivo and human studies indicate that garlic can reduce plasma total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C) accompanied with an increase in high-density lipoprotein cholesterol (HDL-C). The purpose of this review is to provide a comprehensive overview of mechanisms by which garlic consumption influences blood cholesterol levels.

Scopus and PubMed databases were systematically searched and analyzed to identify relevant in vitro, in vivo and randomized clinical trial studies which examined how garlic consumption affected the hypercholesterolemia.

Mechanistic investigations have revealed that garlic exerts its benefits through multiple pathways, including the inhibition of de novo cholesterol synthesis and dietary cholesterol absorption, enhancement of LDL-C uptake, and improvement in HDL-C biogenesis. Recently, garlic extraction and its isolated bioactive compounds have been shown to promote a favorable gut microbiota composition, elevate short-chain fatty acid production, and reduce levels of trimethylamine and trimethylamine N-oxide production. Clinical evidence has shown that long supplementation of garlic for more than two months is effective in reducing plasma cholesterol among individuals whose TC levels are mild to moderate high.

Cholesterol-lowering activity of garlic is mediated by modulating cholesterol synthesis, absorption, and metabolism with an optimal efficacy observed after sustained use in hypercholesterolemic individuals.