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The analysis combined the results of 29 studies with a total of more than 1,500 participants. The researchers included only randomized controlled trials that compared garlic with a placebo, which is the gold standard for any study design and means the meta-analysis is of high quality, says Alyssa Kwan, a registered dietitian who works with patients in the cardiovascular ICU and surgical units at Stanford Health Care in California.
A large body of evidence supports garlic's effectiveness
Overall, the results are consistent with previous studies, which found that garlic may lower A1C levels somewhat and slightly reduce LDL (or “bad”) cholesterol. Matthew Badgett, MDThe integrative medicine physician at the Cleveland Clinic in Ohio was not involved in the study.
According to Badget, every study that looked at A1C levels saw a reduction in levels in those taking garlic, with the average reduction in LDL cholesterol across studies being 8.2 points.
This is a modest effect in terms of lowering “bad” cholesterol, but most studies are likely too short in duration to show garlic's full effect, he says.
“Oftentimes, LDL levels need to be lowered to 150 to 200, and in high-risk patients, they may need to go below 70, and sometimes even lower,” Badgett says.
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 were conducted, researchers say. Elisabetta Politi, MPH, RDShe works as a certified diabetes educator at Duke Health in Durham, North Carolina.
This plant belongs to the Allium family, which also includes onions, leeks, shallots, chives, and scallions. Vegetables from this family contain high concentrations of sulfur compounds such as allicin, alliin, and methylallyl trisulfide, which provide health benefits.
This study had limitations
Overall, Badgett said the analysis has several strengths and weaknesses that should be taken into consideration when looking at the results.
The meta-analysis had a small number of participants, but this is a common problem in supplement studies, which usually do not include many participants.
What's more, there was huge variability in the garlic supplements looked at in the various trials, which could weaken the analysis and make garlic appear less effective than it actually is, Badgett said.
Garlic may be useful as part of a plan that also includes lifestyle changes and medications.
There's clear evidence that garlic is safe and healthy and has some benefits, but it's unlikely to have a significant impact on your health unless you make some big lifestyle changes, Badgett says.
“But that may only be a small part of an effective plan,” he says.
Kwan agrees that while the analysis suggests garlic may be effective in improving cholesterol and blood sugar levels, more evidence, including larger studies, is needed to prove that garlic has these benefits.
Is it better to take garlic supplements or eat foods that contain garlic?
Badgett said there are many types of garlic, including garlic extract, garlic compounds, garlic powder, raw garlic and cooked garlic.
Participants took garlic powder tablets containing between 300 and 22,400 milligrams, and if you like garlic enough, you can include anything within that range in your diet, he says.
“But the problem with eating garlic is that this study looked at daily intake, and I've hardly ever seen anyone eat garlic consistently every day,” Badgett said. Taking a daily supplement would likely produce consistent results, he added.
“If you have trouble digesting garlic or don't like the taste of garlic, I would recommend a garlic supplement, but supplements vary in quality and are expensive, so if you like the taste of garlic and can tolerate it, I would recommend using garlic powder in your food to get the same amount,” Politi says.
Expert tips for adding more garlic to your diet
To get the health benefits of garlic, you need to eat about 3 to 6 grams per day, or 1 to 2 cloves if you like it fresh, says Brogan Taylor, RD, a registered dietitian with Banner Health in Phoenix, Arizona.
To reap all of the potential benefits, Taylor recommends that her clients add fresh garlic, minced or crushed, to their foods.
Garlic is also a great way to flavour foods if you're trying to cut down on your sodium intake, she adds.
Here are some ideas for incorporating more garlic into your diet:
Chili, soup, stew Adding garlic adds flavor and health benefits, Taylor says.
Protein and vegetables Cook proteins like chicken or lean meats with garlic, and use it when roasting or sautéing vegetables, says Taylor. “It can also be added to salad dressings and marinades for a flavorful effect.”
bread Who doesn't love garlic bread? You can also make bruschetta by adding crushed tomatoes and your favorite marinara sauce, says Politi.
Plague Fresh garlic is an essential ingredient in pesto sauce, made with olive oil, basil, Parmesan cheese, and nuts (usually pine nuts), a simple, delicious Mediterranean pasta sauce that Politi says is also heart-healthy.
