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If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
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.
Garlic’s role in heart health
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.
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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.
Additional benefits of garlic
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).
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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.
How to take garlic for heart health
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.
Garlic benefits: crush, chop, or mash garlic to unleash them
Side effects and potential risks
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.
- Arreola, R., Quintero-Fabián, S., López-Roa, R. I., Flores-Gutiérrez, E. O., Reyes-Grajeda, J. P., Carrera-Quintanar, L., & Ortuño-Sahagún, D. (2015). Immunomodulation and anti-inflammatory effects of garlic compounds. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4417560/
- Assmann, G., Cullen, P., Schulte, H., Hata, Yoshiya, Aviello, G.,et al. (2010). The effects of time-released garlic powder tablets on multifunctional cardiovascular risk in patients with coronary artery disease. Lipids in Health and Disease, 9(119): 110. Retrieved from https://lipidworld.biomedcentral.com/articles/10.1186/1476-511X-9-119
- Banerjee, S. K. & Maulik, S. K. (2002). Effect of garlic on cardiovascular disorders: a review. Nutrition Journal, 1, 4. doi: 10.1186/1475-2891-1-4. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC139960/
- Gander, K. (2019, September 12). Eating garlic linked to better memory in Alzheimer’s study on mice. Retrieved from https://www.newsweek.com/eating-garlic-linked-better-memory-alzheimers-study-mice-1388600
- Inal, D., Tiryaki, G., & Levent, M. (2000) Effects of Effects of Garlic on Aerobic Performance. Turkish Journal of Medical Sciences, 30, 557-561. Retrieved from https://www.semanticscholar.org/paper/Effects-of-Garlic-on-Aerobic-Performance-Ince/685e7746a865751cc421acdf60cfd8d4ace19cfd?p2df
- Kianoush, S., Balali-Mood, M., Mousavi, S. R., Moradi, V., Sadeghi, M., Dadpour, B., et al. (2012). Comparison of therapeutic effects of garlic and d-Penicillamine in patients with chronic occupational lead poisoning. Basic Clinical Pharmacology and Toxicology, 110(5): 476-481. doi: 10.1111/j.1742-7843.2011.00841.x. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22151785
- Mukherjee, M., Das, A. S., Mitra, S., & Mitra, C. (2004). Prevention of bone loss by oil extract of garlic (Allium sativum Linn.) in an ovariectomized rat model of osteoporosis. Phytotherapy Research, 18(5): 389-394. doi: 10.1002/ptr.1448. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15173999
- Sears, M. E. (2013). Chelation: harnessing and enhancing heavy metal detoxification–a review. Scientific World Journal, 2013: 219840. doi: 10.1155/2013/219840. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3654245/#sec3title
- Zeng, T., Guo, F. F., Zhang, C. L., Song, F. Y., Zhao, X. L., & Xie, K. Q. (2012). A meta-analysis of randomized, double-blind, placebo-controlled trials for the effects of garlic on serum lipid profiles. Journal of the Science of Food and Agriculture, 92(9): 1892-1902. doi: 10.1002/jsfa.5557. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22234974
Dr. Mike is a licensed physician and the Director, Medical Content & Education at Ro.