Despite decades of conflicting studies about the herb's ability to improve heart health, the researchers say their study provides the most rigorous evidence to date that consuming garlic on a daily basis, in the form of either raw garlic or two of the most popular garlic supplements, does nothing to lower LDL cholesterol levels among adults with moderately high cholesterol levels.

Christopher Gardner of the cholesterol in California, says despite the widespread claims of the herb's power, it does not work.

Gardner says there is no shortcut; good health is achieved by eating healthy food and there is no pill or herb that counteracts an unhealthy diet.

Gardner says some of the claims that garlic lowers cholesterol are derived from laboratory experiments but there is no proof it reacts in the body in the same way.

Gardner says in test tubes and in some animal subjects the compound released from crushed garlic, allicin, a sulfur-containing substance, has been found to inhibit the synthesis of cholesterol.

Gardner carried out a study involving 192 subjects who had slightly elevated levels of low-density lipoprotein (LDL).

The participants were divided into four groups: one ate a clove of garlic six days a week, usually in a gourmet sandwich prepared for them; two other groups consumed the equivalent amount of garlic either in a popular garlic supplement pill or powder, one of which advertised itself as "aged" garlic that removed the bad-breath problem; and the other group consumed a placebo.

Cholesterol levels in the group ranged from 130 milligrams per deciliter of blood to 190 milligrams; a higher amount would have entailed the prescribing of cholesterol-lowering statin drugs.

Gardner says the study had the statistical power to see any small differences that would have shown up, and lasted long enough for them to see whether it might take a while for the the garlic to take effect.

The participants were also divided into those with the highest as against those with the lowest LDL cholesterol levels at the start of the study.

Participants were closely monitored throughout the study to ensure that they didn't gain or lose weight, which might have affected their cholesterol readings.

Cholesterol measurements were taken every month for six months and the results says Gardner were identical.

Gardner believes other health claims attributed to garlic also need to be examined.

Garlic's healthy reputation is historical and dates back to the ancient Egyptians, the Greeks and the Romans.

Its juice has also been used as an antiseptic and it is possible its assumed benefits may be due to its abundance around the Mediterranean, where diets are often rich in healthy olive oil, fish, nuts and fruit.

Gardner says garlic is a useful addition to flavour and spices up healthy dishes, such as stir fry or Mediterranean salads, but anyone choosing garlic fries as a cholesterol-lowering food, has 'blown it'.

The study used the expertise of two of the nation's foremost garlic experts - Larry Lawson, PhD, of the Plant Bioactives Research Institute in Utah, and Eric Block, PhD, professor of chemistry at the University at Albany, State University of New York.

Both have devoted much of their careers to understanding the biochemical properties of the herb and they ensured the quality and stability of the garlic consumed in the study.

The study is the first independent, long-term, head-to-head assessment of raw garlic and garlic supplements and was funded by the U.S. National Institutes of Health.

The study is published in the Archives of Internal Medicine.