Can garlic help lower cholesterol and blood sugar levels?

According to the Centers for Disease Control and Prevention (CDC), diabetes affects millions of people per year. Approximately 11.6% of people in the United States have diabetes.

The CDC also reports that around 86 million adults 20 years and older in the U.S. have elevated cholesterol levels. This can lead to developing heart disease or having a stroke.

One way medical professionals monitor these conditions is by checking blood levels. During a routine checkup, healthcare providers often order blood tests that check the patient’s cholesterol, fasting blood glucose, HbA1c, and triglyceride levels.

Depending on the results of these tests, the provider gets an idea of whether someone is in the process of developing a health condition such as diabetes or high cholesterol.

For people who are at risk or have developed a condition, doctors can put in place interventions to reduce the chances of developing the disease or treat it with medications and lifestyle changes.

The researchers in the current study were curious whether garlic could impact lipid levels and blood glucose levels.

Garlic has a compound called allicin, which a previous review study reported to have properties such as being antibacterial, antifungal, and antiviral. A prior study also showed that allicin was effective at lowering cholesterol in an animal trial.

To see whether garlic can improve blood glucose and lipid metabolism, the researchers analyzed 22 studies meeting their criteria, which included 29 trials to focus on for their meta-analysis. These trials involved a total of 1,567 participants from different countries and age groups.

To qualify for inclusion, trials needed to use garlic as an intervention for more than 2 weeks and report on HbA1c, fasting blood glucose, total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglycerides.

The researchers also only considered studies with participants ages 18 and older and studies with control groups.

The researchers in the various trials administered garlic in different forms:

• garlic powder
• garlic oil
• aged garlic extract
• garlic powder pill or tablet
• garlic extract capsule
• raw garlic.

Depending on the trial, some participants consumed 300 to 22,400 milligrams (mg) of garlic powder per day, while other preparations ranged from 800 to 4,200 mg daily.

At the end of those trials, the researchers collected information on the participants’ blood levels to compare to their baseline levels.

The researchers conducting the current meta-analysis used all these data to see whether garlic consumption could improve metabolic markers.

The meta-analysis found a significant association between garlic intervention and improvement in different metabolic markers.

Garlic supplementation lowered fasting blood glucose levels, HbA1c, total cholesterol, and low-density lipoprotein cholesterol — also referred to as “bad cholesterol.”

Additionally, the garlic intervention increased high-density lipoprotein cholesterol levels, also known as “good cholesterol.”

“Elevated fasting blood glucose and HbA1c are characteristic of type 2 diabetes mellitus,” note the authors, highlighting the significance of these findings. The researchers also said that the longer the garlic intervention trial lasted, the more improvement participants saw in their fasting blood glucose, total cholesterol, and low-density lipoprotein cholesterol levels.

While the researchers found improvements in other blood markers, they did not find an impact on triglyceride levels.

The study findings show that garlic interventions may have the potential for use in either preventing or managing some cardiovascular and metabolic disorders.

“The intervention of garlic is beneficial to control blood glucose and blood lipids in humans,” write the authors.

Cheng-Han Chen, MD, a board-certified interventional cardiologist and medical director of the Structural Heart Program at MemorialCare Saddleback Medical Center in Laguna Hills, CA, discussed the research — in which he was not involved — with Medical News Today.

“This meta-analysis included many different trials that studied the effects of garlic,” said Chen. “However, these studies varied quite a bit in their designs, and thus do not allow us to pinpoint the exact active compounds that could be responsible for garlic’s beneficial effects.”

Chen further noted that experts believe “garlic has beneficial effects on blood sugar control and cholesterol levels through its sulfur-based compounds, such as allicin, alliin, and diallyl disulfide,” but that more research is necessary to learn exactly how it works.

“This study is unlikely to change our specific dietary recommendations, but it should be noted that garlic would be considered a nutritious and healthy addition to any diet,” he told us.

Edwin Bosa-Osorio, MD, a faculty member in the Family Medicine Program at the Brodes H. Hartley, Jr. Teaching Health Center at Community Health of South Florida, also spoke with MNT and discussed the study’s strengths and weaknesses. Bosa-Osorio was not involved in the current research either.

“While the findings are interesting and bear further study, this is not what we would call a ‘high-powered’ study given the low sample numbers and limited durations,” he explained.

Bosa-Osorio pointed out that many of the trials included in the study meta-analysis had a low participant level, saying that “[of]f those 22 studies, many had low sample sizes, the highest being below 200 persons studied, and others numbering only a hundred or so.”

He also did not foresee any changes to dietary recommendations in the near future:

“If these indications are truly valid, pending further studies, there could be an impact on dietary recommendations. But right now, when it comes to primary prevention for heart disease and type 2 diabetes, we already have proven very highly effective treatments and primary preventative methods.”