What is garlic's role in heart health?

Garlic—that bane of vampires and daters—might be worth embracing for your health. The white bulbous herb, also known as allium sativum, is a cousin of the onion, leek, and chive. For thousands of years, garlic has been used as a seasoning; some cultures have also used it for medicinal purposes to treat a wide range of conditions.

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Garlic contains a natural chemical called allicin, which breaks down into a substance called allicin when the herb is cut, chewed, or mashed. Allicin turns into several compounds, including hydrogen sulfide, which is responsible for the herb's unmistakable smell and taste. It's believed that allicin and other natural compounds in garlic relax blood vessels and have anti-inflammatory effects, which may lower blood pressure and benefit heart health. 

In studies, researchers have found that garlic may have several health benefits. But reviews of the research note that further study is needed to confirm the effects of garlic on heart health. While we describe many of the potential benefits of garlic below, it is important to keep in mind that these studies may have only been conducted in animals, in a few people, or in people with specific health conditions. As a result, it is likely these benefits would not be seen by everybody taking garlic supplements.

Garlic may improve cholesterol levels

Consuming more garlic might have beneficial effects for people who've been diagnosed with high cholesterol. A meta-analysis of 26 studies found that garlic was superior to placebo in reducing levels of total cholesterol and triglycerides (a type of fat) in the blood (Zeng, 2012). Garlic is believed to reduce buildup on the walls of arteries that can cause the clogging that leads to cardiovascular diseases like heart attack or stroke (Banerjee 2002). 

Garlic may reduce blood pressure

According to a review of studies published in Nutrition Journal, increased consumption of garlic is associated with a lower incidence of hypertension (high blood pressure) (Banerjee, 2002). Garlic seems to increase the body's production of nitric oxide, which relaxes smooth muscles and widens blood vessels, causing blood to flow more freely and reducing blood pressure.

Garlic may prevent blood clots

In one study of people with peripheral occlusive arterial disease, patients who took an 800 mg garlic powder supplement for 12 weeks experienced a "significant decrease" in the thickness of their blood (Banerjee, 2002). Another study found that people with coronary artery disease taking a garlic powder supplement had less "platelet aggregation," or blood cells sticking together. Thick, sticky blood can lead to blood clots, stroke, and heart problems (Assmann, 2010). 

Garlic may regulate heart rate

In animal studies, garlic has been found to have a "significant antiarrhythmic effect" (Banerjee, 2002), stabilizing irregular heartbeats. In humans, atrial fibrillation is an irregular heartbeat that is linked to an increased risk of blood clots, stroke, and heart failure, among other cardiovascular issues.

Garlic might fight disease

Garlic has natural antibacterial and antiviral properties, and researchers believe it can strengthen the immune system (Arreola, 2015), decreasing inflammation and stimulating the production of "killer cells," which are agents in the body that combat infection. 

Garlic may help prevent Alzheimer’s disease and dementia

Garlic may have positive effects on memory. That was the conclusion of a recent study at the University of Louisville, in which researchers fed 24-month-old mice (the equivalent of 56- to 69-year-old humans) allyl sulfide, a compound found in garlic. They found the mice had better short- and long-term memory skills than those who didn't take the compound. The scientists speculate that garlic may be able to turn up the expression of a gene, NDNF, which affects memory (Gander, 2019).   

Garlic may improve athletic performance

Garlic is a vasodilator, which causes blood vessels to relax and improves blood flow. Other natural vasodilators, like beet juice, have been found to improve athletic performance, and garlic may have promise in that area: In one study, college endurance athletes who took a garlic powder supplement before running had a "significant increase" in maximum oxygen consumption (VO2max) and endurance performance time five hours later (Inal, 2000).

Garlic detoxifies heavy metals

Clinical studies show that the sulfur present in garlic may be able to detoxify heavy metals in the body, including preventing cadmium-induced kidney damage and decreasing oxidative damage from lead (Sears, 2013). One study found that employees of a car battery plant who took a garlic supplement for 12 weeks had 19% less lead in their blood, and experienced fewer symptoms of lead poisoning, than workers who took the drug D-penicillamine, which is a medication commonly used in cases of heavy metal poisoning (Kianoush, 2012).

Garlic may improve bone health

Animal studies have found that taking a garlic oil supplement increased the bone density of mice who had low levels of estrogen (Mukherjee, 2004). Osteoporosis is a particular risk for women after menopause when estrogen levels decline.

If you're looking to reap the beneficial effects of garlic, first, you can increase your garlic consumption by adding more raw garlic to your diet. You can add fresh garlic to salads, egg scrambles, healthy dressings and sauces, and meat dishes. Or if you're feeling hardcore, you can eat whole garlic cloves.

You can also take garlic supplements, which come in many forms. Garlic pills may include garlic powder or aged garlic extract (like Kyolic). Garlic oil is also available. Always exercise caution when choosing dietary supplements—because they're not regulated as pharmaceuticals are, purity and quality isn't guaranteed. This also means there is no known “ideal” amount to ingest per day to see the health benefits.

Like just about everything, garlic can be toxic if it's taken in high doses. The Office of Dietary Supplements at the National Institutes of Health says that garlic is safe at the amounts naturally present in food but doesn't advise on the tolerable upper limit for garlic supplements.

Side effects of consuming garlic can include breath and body odor, heartburn, and other digestive upset. Some people might have an allergic reaction to garlic.

Taking garlic supplements may increase the risk of bleeding. If you take a blood-thinning medication such as warfarin (brand name Coumadin), tell your healthcare provider if you plan to take garlic dietary supplements. Garlic has also been found to lessen the effectiveness of some drugs, including saquinavir, which is used to treat HIV.

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How we reviewed this article

Every article on Health Guide goes through rigorous fact-checking by our team of medical reviewers. Our reviewers are trained medical professionals who ensure each article contains the most up-to-date information, and that medical details have been correctly interpreted by the writer.

Editorial Guidelines | Medical Review Process

Current version

November 03, 2019

Written by

Michael Martin

Fact checked by

Mike Bohl, MD, MPH, ALM

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About the medical reviewer

Mike Bohl, MD, MPH, ALM

Dr. Mike is a licensed physician and a former Director, Medical Content & Education at Ro.