The current analysis pooled the results of 29 studies with a combined total of more than 1,500 participants. Investigators only included randomized control trials that compared garlic with a placebo control, which is the gold standard for any research design and means the meta-analysis is high quality, says Alyssa Kwan, RD, a registered dietitian working with people in the cardiovascular ICU and surgery units at Stanford Health Care in California.
A Large Body of Evidence Confirms Garlic’s Benefits
Overall, the findings agree with what previous studies have shown: Garlic leads to some decrease in A1C levels and a small reduction in LDL (or “bad”) cholesterol, says Matthew Badgett, MD, an integrative health physician at Cleveland Clinic in Ohio, who was not involved in the study.
All the included studies that looked at A1C levels found a decrease in the group taking garlic, and the average LDL cholesterol reduction across the studies was 8.2 points, says Dr. Badgett.
That’s a modest benefit when it comes to lowering “bad” cholesterol, though many studies were likely too short to show the full benefit of garlic, he says.
“We often need to lower LDL from 150 to 200, to less than 70 in high risk patients, and sometimes even more,” says Badgett.
Garlic Has a Long History in Traditional Medicine
Garlic has been used for its medicinal properties for thousands of years, long before studies like this one were conducted, says Elisabetta Politi, MPH, RD, who works as a certified diabetes educator at Duke Health in Durham, North Carolina.
The plant is part of the allium family, which also includes onions, scallions, shallots, chives, and leeks. Vegetables in this family contain high concentrations of sulfur compounds, including allicin, alliin, and methyl allyl trisulfide, which contribute to the health benefits.
The Study Had Some Limitations
Overall, the analysis has some strengths and weaknesses that should be considered when viewing the findings, Badgett says.
For a meta-analysis, the number of participants was small — which is often a problem with supplement studies, because they usually don’t enroll a lot of people.
Additionally, the garlic supplements examined in the different trials are extremely variable, which weakens the analysis, and probably makes the benefit of garlic look weaker than it is, says Badgett.
Garlic May Help as Part of a Plan That Includes Lifestyle Changes and Medications
There’s clear evidence that garlic is safe, healthy, and yields some benefit. Without bigger lifestyle changes, though, it’s not likely to have a significant impact on your health, says Badgett.
“But it can be one small piece of an effective plan,” he says.
Kwan agrees that although the analysis suggests that garlic can be beneficial for improving cholesterol and blood sugar levels, more evidence, including larger studies, are needed to show that garlic is causing these benefits.
Which Is Better, Taking a Garlic Supplement or Eating Foods With Garlic?
There are many types of garlic, including garlic extracts, garlic compounds, garlic powder, raw garlic, and cooked garlic, says Badgett.
The participants consumed between 300 and 22,400 milligrams of garlic powder tablets. We can eat within that range at meals if we like garlic enough, he says.
“But the issue with eating garlic is that the study looked at daily consumption, and I rarely see people eat garlic consistently every single day,” says Badgett. People would be more likely to see consistent results by taking a daily supplement, he adds.
“For clients who don’t digest garlic well or don’t like the taste of it, I do recommend supplements. But because of the variations in supplement quality and the expense, I think using garlic powder in foods to get the equivalent amount may be preferable — if you like the taste and you tolerate it,” says Politi.
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