Lipid-Lowering Effects of Garlic

It was demonstrated previously that allicin extracted from garlic had a lipid-lowering effect on long-term feeding to healthy rats. These studies reported a significant decrease in total serum lipids, phospholipids, and cholesterol in the animals fed allicin compared to control animals. 

The cholesterol-lowering effect of garlic was also seen in rabbits that were fed 2 g choles-terol/day for 16 weeks. A dose-dependent reduction of serum cholesterol in garlic-fed rats was observed in these experiments. 

A study carried out in the U.S. showed a 56% decrease in serum total lipid radioactivity in rats fed the equivalent of 5 g of fresh garlic bulbs/d for 7 d. Rats fed an experimental diet containing cholesterol were treated either with intraperitoneal injections of C-14 labeled acetate or a diet containing C-14 sucrose. 

In summary, the consumption of garlic appears to reduce serum cholesterol in experimental animals in a dose-dependent fashion. This may be due to decreased synthesis or increased excretion of cholesterol through the intestinal tract. It has been reported that garlic consumption increases high-density lipoprotein (HDL) levels, which may help to remove excess cholesterol from arterial tissue. 

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In vitro, allicin and related compounds inhibit HMG-CoA reductase, which is involved in cholesterol biosynthesis (see Chapter 35 Agents Used in Hyperlipidemia). Several clinical trials have investigated the lipid-lowering potential of garlic. Some have shown significant reductions in cholesterol and others no effect. The most recent meta-analysis suggested a minor (5%) reduction of total cholesterol that was insignificant when dietary controls were in place. 

Sumioka, L, Hayama, M., Shimokawa, Y., Shiraishi, S., Tokunaga, A., and Hiroshima, J. 2006. Lipid-lowering effect of Monascus garlic fermented extract (MGFE) in hyperlipidemic subjects. Med. Sci. 55(2), 59-64. 

The cardiovascular diseases and thrombotic diseases, which would be attributed more or less to the atherosclerosis, have been increased recently, and are the leading cause of death especially in the industrialized countries. The intake of garlic and onion is supposed to benefit in lowering the mortality and morbidity rates of these diseases by their antithrombotic, lipid-lowering, and hypoglycemic effects. In this section, antithrombotic and anticardiovascular effects of garlic and onion are described. 

Garlic has been reported to have lipid- and blood-pressure-lowering properties, as well as antiplatelet, antioxidant, and fibrinolytic effects. In animal models and human cell cultures, it has been shown to have antiatherosclerotic activity (see Chapter 50). The sulfur-containing component, allicin, is considered to be the principal active ingredient of garlic, but several other bioactive ingredients have also been isolated. 

Garlic is the bulb of Allium sativum L. and was first cultivated in ancient Egypt, Greece, Rome, India, and China for its safe and effective therapeutic benefits as well as culinary uses. It has been used to treat tumors, headaches, weakness and fatigue, wounds, sores, and infections. It lowers blood lipids and inhibits platelet aggregation. 

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