Hugely popular garlic supplements do not pass the scientific smell test when it comes to lowering cholesterol levels, a study out of Stanford University says.

One of the best-selling herbal medicines – and one that's been used for thousands of years to improve heart health – garlic has "zero" impact on human cholesterol levels, says the study, published yesterday in the journal Archives of Internal Medicine.

"There was absolutely no impact (on cholesterol levels)," says Christopher Gardner, an assistant professor in the California school's department of medicine and the lead study author.

The research involved 192 patients with moderately elevated LDL (or bad) cholesterol levels.

Scientists found that neither raw garlic nor two popular derivatives of the pungent herb had any cholesterol reducing properties.

"It was very disappointing, I have to say," says Gardner, who works at the Stanford Prevention Research Centre.

"We really thought, actually, that the fresh garlic would work and then we were really curious which of the garlic supplements would measure up to the fresh garlic."

Instead, during head-to-head competition, the garlic products actually fared a little worse as cholesterol reducers than the placebos.

Garlic product manufacturers typically sell their concoctions on claims they lower cholesterol and blood pressure, says Heather Boon, associate professor in the University of Toronto's Leslie Dan Faculty of Pharmacy.

"It's been used for those particular (heart-oriented) uses for thousands of years," says Boon.

"It's one of the oldest medicinal remedies that we know of."

Julie Daniluk of The Big Carrot Natural Food Market in Toronto says garlic is "incredibly popular" as a herbal remedy, so much so that it warrants its own section in her popular Danforth Ave. facility.

Daniluk, the store's nutritionist, says garlic's popularity is based largely on its touted cholesterol-lowering properties, as well as its claims to antibacterial and immunological benefits.

"It's also sold widely as a lung support, because as you eat garlic, when you digest it, the garlic oil can actually bubble up through the lungs," she says.

"And that does kill the bacteria in the lungs, so it's used also when people have colds."

Daniluk says previous studies have confirmed garlic's use as a cholesterol reducer.

All of the participants in the six-month Stanford study were given supplement or placebo pills and "heart-healthy gourmet" sandwiches, some with and some without fresh garlic.

Those who were given placebo pills were fed the garlic bearing sandwiches while those receiving the actual supplement pills were given sandwiches without any garlic.

After more than 30,000 sandwiches and thousands of pills, however, researchers could find no significant cholesterol reduction in any of the study participants.

Gardner says there have been several previous studies in animal and cell culture models that suggested garlic might have a cholesterol-lowering impact.

"There are (also) 30 or 40 human clinical trials on this and the frustrating thing is half have said `yes' and half said `no'," Gardner says.

"But they were all funded by the supplement industry. They are all supplement studies."

Boon says the study did not come as a huge surprise to her, as previous research has shown little or no cholesterol-related properties for garlic supplements.

Gardner, whose research was funded by the U.S. National Institutes of Health, says the new study suggests that neither fresh garlic nor any of the available supplements affect cholesterol in humans.

He says none of the previous human studies used fresh garlic and that if it didn't work to lower cholesterol, there would be little possibility that any derivative supplement would either.

But Gardner says his study does not kill garlic's potential usefulness as a cholesterol-lowering substance.

He says fresh garlic could be used to improve the taste of healthy foods, to make them more palatable to those not used to eating them.

As well, he says, the study did not look at the potential role of garlic in preventing heart attacks or cancer, some of the other claims that have been made of the plant.

"However, none of those have been substantiated either with a definitive, human clinical trial."