Those who count on eating raw garlic or taking garlic supplements to get their serum cholesterol under control, may not want to hear this, but a new Stanford University School of Medicine study has found that the herb does not help lower low-density lipoprotein or LDL or bad cholesterol. The study was published in the Feb. 26 issue of the Archives of Internal Medicine

The study on the effect of garlic on plasma cholesterol was conducted by a number of "heavy weight" experts including 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 - who understand the biochemical properties of the spice and helped ensure the quality and stability of the garlic consumed in the study.

Many studies have been conducted to investigate the possible effect of garlic on cholesterol, but results are inconsistent or conflicting.   

One early study published in the December 2006 issue of American Journal of Clinical Nutrition by M BA van Doorn and colleagues found that garlic preparation has no effect on plasma lipids such as total cholesterol and LDL cholesterol in 90 overweight subjects aged 40 to 75.

Another study, which is more encouraging, published in Journal of the American College of Nutrition, vol. 20. No. 3 2001 by David Kannar and colleagues found that enteric-coated garlic power supplements with 9.6 mg allicin-releasing potential may help patients with mild to moderate hypercholesterolemia when a low fat diet was also used.   In the study of 46 subjects, the supplement reduced total cholesterol by 4.2 percent and LDL cholesterol by 6.6 percent.   The researchers suggest in their article that the efficacy of garlic for lipoprotein metabolism might require certain degree of allicin bioavailability.

The researchers of the current study said that their study, believed to be most rigorous provides evidence proving that garlic does not help lower LDL cholesterol among men and women with moderately high levels of LDL cholesterol.

"It just doesn't work," said senior author Christopher Gardner, PhD, assistant professor of medicine at the Stanford Prevention Research Center. "There's no shortcut. You achieve good health through eating healthy food. There isn't a pill or an herb you can take to counteract an unhealthy diet."

"If garlic was going to work, in one form or another, then it would have worked in our study," Gardner said. "The lack of effect was compelling and clear. We took cholesterol measurements every month for six months and the numbers just didn't move. There was no effect with any of the three products, even though fairly high doses were used."

According to the researchers, most of the early medicinal claims over garlic's cholesterol lowering benefit are based on the fact that the sulfur-containing substance known as allicin, which is produced when raw garlic is chopped or crushed, inhibits the synthesis of cholesterol in test tubes and in animals.   However, the benefit has not consistently been demonstrated in humans.

"In lab tests, you can apply the garlic compounds directly to cells," Gardner said. "But in real people you don't know whether allicin would actually get directly to cells if someone ate garlic. You still have to do the human clinical trial to see if it really works, and the previous clinical trials left people confused."

There is another fact that garlic supplement makers may claim is that garlic possesses antioxidative properties and naturally it may be assumed that it protects against oxidation of LDL cholesterol and the protection may benefit people with high levels of cholesterol.

The current study was conducted in 192 patients who had moderately elevated LDL cholesterol levels ranging from 130 to 190 mg/dL with an average level of about 140 mg/dl when entering the study.  They were assigned into four groups to receive four types of treatments, raw garlic, garlic power, aged garlic extract and placebo 6 days per week for six months. According to the study, the amounts used in the study were standardized to one average-sized garlic clove (about 4 grams).

Garlic was used in 3 forms with raw garlic from California Early; Christopher Ranch, Gilroy, California, 2 commercial supplements, Garlicin from Nature's Way Products Inc, Springville, Utah and Kyolic-100 from Wakunaga of America Co, Mission Viejo, California.

All of the study participants were given tablets as well as sandwiches with 370 kcal calories in each Sandwich and no more 10 percent saturated fat prepared by Gardner's team who acknowledged that the sandwiches may have affect on the serum cholesterol, but the study was so designed to minimize the potential influence.

During the study, the researchers monitored LDL-C concentration as primary study outcome. Fasting plasma lipid concentrations were also assessed on a monthly basis. They also monitor participants closely to ensure they did not gain or lose weight, which might have affected their cholesterol readings.

What was found is that the LDL cholesterol levels were essentially the same in blood samples collected at the start and the end of the study from all four groups.   The groups receiving garlic or garlic supplements seemingly experienced an insignificant increase while a tiny drop was seen in the placebo group.

"Our study had the statistical power to see any small differences that would have shown up, and we had the duration to see whether it might take a while for the effect of the garlic to creep in. We even looked separately at the participants with the highest vs. the lowest LDL cholesterol levels at the start of the study, and the results were identical," Gardner said. "Garlic just didn't work."

The Stanford University issued a press release saying that "One potential reason for the confusion surrounding garlic's reputed health benefits is that the supplement makers themselves funded many of the previous studies claiming that garlic lowered cholesterol. Gardner's funding came from the National Institutes of Health."   But critics suggest that funding from the National Institutes of Health does not necessarily mean free of influence from the sponsor.

Regardless of its effect on cholesterol, Gardner said garlic may still have an effect against other diseases or conditions that were not addressed in the study including inflammation, immune function or cancer. But, again, he added that those health claims must also be confirmed in rigorously controlled trials.

He also said that garlic can still be valuable part of everyone’s diet. "But if you choose garlic fries as a cholesterol-lowering food, then you blew it. The garlic doesn't counteract the fries," Gardner said.

A scientist affiliated with foodconsumer.org comments that the conclusion the researchers made that garlic has no effect on cholesterol was based on one single dose, meaning that any effect of other doses remains unknown.

He suggests that there may be some drawbacks in the study.   First, participants were instructed to microwave the garlic-containing sandwiches before eating them.   This means that the active components in garlic and garlic supplements that would otherwise have a potential cholesterol lowering effect might have been destroyed.  The conclusion may not be applicable to the garlic people use every day, which is seldom subjected to microwaving.

Secondly, he suggests, the effect of sandwiches per se on the serum cholesterol was unknown.   Although the study was so designed to minimize its effect on the study outcomes among four arms of the study, high dietary intake of cholesterol-promoting or dietary cholesterol from foods could overwhelm the garlic cholesterol lowering effect if there is any.  

Thirdly, there was no reporting of what else the participants ate other than the garlic sandwiches each day over the six entire months.   A typical American diet consists of high levels of cholesterol.   The foods in one's diet may have a significant effect on the serum cholesterol.  

He suggests that consumers need to know a few things.  First, the conclusion of the current study has its own limitations, meaning that the conclusion may not be generalized to a real consumption of garlic.  Second, one should never count on garlic to lower their cholesterol in the first place.   Third, one should continue using garlic as this pungent herb does not only offer a unique flavor, but also other health benefits such as helping fight a host of cancer among others.

The best way to naturally reduce the LDL cholesterol without resorting to garlic, the health observer says is to lower dietary intake of LDL cholesterol. That means one needs reduce intake of meat and dairy products although few people would be able to follow such a restricted dietary regimen.

Source
 

Effect of Raw Garlic vs Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia: A Randomized Clinical Trial
Christopher D. Gardner, PhD; Larry D. Lawson, PhD; Eric Block, PhD; Lorraine M. Chatterjee, MS; Alexandre Kiazand, MD; Raymond R. Balise, PhD; Helena C. Kraemer, PhD
Arch Intern Med 2007;167:346-353.

ABSTRACT | FULL TEXT