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Garlic and Cholesterol

Cholesterol - a white, waxy substance found in the blood plasma - is essential to life. However overly high cholesterol levels can have serious health implications on the cardiovascular system in particular leading to atherosclerosis. Excessive levels can be an indicator of increased risk of heart attack and/or stroke.

If you suspect that you have a cholesterol problem it is essential that you discuss it with your doctor.

Whilst all cholesterol was once considered harmful, it is now recognised that it comes in two distinct forms: one "good", the other "bad".

Good and Bad Cholesterol

HDL and LDL

Cholesterol comes in two forms: high-density lipoproteins (HDLs) and low-density lioproteins (LDLs). Of these, HDLs are generally called "good" cholesterol whilst LDLs are "bad". For more detail see the LDL & HDL cholesterol page.

2005 UK recommendations (from the Joint British Societies - JBS2) are total cholesterol below 4.0mmol/l, "bad" cholesterol below 2.0mmol/l (1). Obviously these are general guidelines which may not be appropriate for everyone.

The Possible Effect of Garlic on Cholesterol Levels

Garlic has been reputed to assist the heart for centuries and has been used in herbal medicines for all manner of conditions. Garlic & cholesterol reduction are frequently mentioned together.

Modern medical science suggests one reason garlic might reduce cholesterol: garlic is a proven anti-oxidant (2). This property might help to prevent LDLs from being oxidised. In this way the cholestrol build-up that clogs the arteries could perhaps be reduced by garlic.

In recent decades, numerous scientific studies have been conducted to test the claims that garlic can help lower cholesterol levels. These studies involve measuring the cholesterol and triglyceride levels of patients taking garlic supplements compared with a control group of patients taking a placebo. Unfortunately the results are not conclusive (3).

Some studies have shown a reduction in total cholesterol levels and/or LDL levels in those taking garlic. Other medical studies have shown no significant difference between the levels of those taking garlic and those taking a placebo. A study published in 2007 (4) tested raw garlic and two popular garlic supplements (Garlicin and Kyolic). The study concluded that: "None of the forms of garlic used in this study, including raw garlic, when given at an approximate dose of a 4-g clove per day, 6 d/wk for 6 months, had statistically or clinically significant effects on LDL-C or other plasma lipid concentrations in adults with moderate hypercholesterolemia."

Cholesterol and Garlic: The Verdict

Can Garlic Lower Cholesterol Levels?

So, does it work? Whilst some individual studies have shown that garlic can be effective in reducing "bad" cholesterol (LDLs), the overall body of evidence is inconclusive. In particular the 2007 study appears to shed serious doubt on the reality behind garlic's reputation in this area. Thus it would be unwise to draw a definite conclusion that garlic can be used to combat "bad" cholesterol foods.

How then do we explain those studies that do show garlic works as a cholesterol treatment? Do we simply discard them as using flawed methodology? If - for the sake of argument - we assume there is some validity in those that found links, how do we explain the different findings? One possibility is that the efficacy of garlic in combatting cholesterol etc depends upon some other, unknown factor - for example the exact variety or manner of preparation of the garlic. Since this factor is unknown, it is not possible to design tests to eliminate it. Another possibility is that the reputed cholesterol lowering properties of garlic are effective only for specific subgroups of the population.

If you are concerned about elevated cholesterol levels then you should not turn to garlic as an alternative to medical treatment - get advice from your doctor. However if your doctor approves then you might like to consider eating more garlic as part of a balanced diet "just in case". If nothing else it's a tasty alternative to salt.

References:

(1): Your Cholesterol Number
(2): Antioxidant Activity of Allicin, an Active Principle in Garlic
(3): Health Effects of Garlic: American Family Physician
(4): Effect of Raw Garlic vs Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia