Does Garlic Reduce Your Risk of Cancer?

Alliums in garlic may play a role in both cancer prevention and treatment

Garlic may have benefits that go beyond flavoring food. It has been shown to have antibacterial and antioxidant properties. It has also been linked to a reduced risk of developing certain cancers.

Although there is still much to be learned about the exact role garlic might play in reducing the risk of cancer, it might have some benefits in cancers of the gastrointestinal (GI) tract as well as the breast and prostate.

This article will review the properties of garlic that provide its health benefits, as well as the conditions it may be helpful for, how it can be used, and warnings.

Garlic
Amarita / iStockphoto

Garlic Basics

Garlic and onions have been a part of cooking since ancient times. The fragrant garlic plant has been called by many names, including "the bulb of the tree of life" for its antiaging properties.

Garlic is a vegetable in the Allium family of bulb-shaped plants. It grows in several sizes and colors and can be planted alongside other vegetables as a natural pesticide.

Although dining on garlic-flavored foods may give you "garlic breath," this food is believed to help improve health by lowering high blood pressure and "bad" (LDL, low-density lipoprotein) cholesterol levels. The health benefits of garlic also include its natural antibiotic action that prevents the growth of bacteria, antioxidant action to help fight free radical damage, and anti-inflammatory properties, all of which may help prevent cancer.

Garlic contains high levels of sulfur, flavonoids, and selenium. And, when it is crushed, chopped, or bruised, garlic produces the compound allicin.

Allicin can have an effect on cells called signaling cells, which control cell growth.

Three of the cancer-fighting compounds in garlic are:

  • Allicin: This plant compound is antibiotic and antifungal (inhibits the growth of fungi). Raw is best since cooking speeds the breakdown of allicin, and microwaving appears to destroy it and eliminate the health benefits.
  • Flavonoids: These are aromatic plant compounds that are considered to have antioxidant and anti-inflammatory (prevents or reduces inflammation) properties. These compounds can help fight cancer by preventing cell damage.
  • Selenium and allyl sulfides: These substances keep cell DNA from being damaged—DNA damage is the root cause of cancer.

Health Benefits

When looking at the potential benefits of garlic in relation to cancer prevention, it's helpful to search for studies that examined a relationship between eating large amounts of garlic and its effect on rates of cancer. Multiple studies have been done on garlic and its role in cancer prevention.

Cancer Reduction/Prevention

Garlic has been associated with a reduced risk of the following cancers:

How Garlic May Reduce the Development of Cancer

Many processes are present when cancer starts to grow, but it all starts with the DNA inside of a cell becoming abnormal. A normal, healthy cell is made in a very predictable process, and then, at the proper time, it undergoes cell death.

The abnormal DNA in cancer cells causes them to make new cancer cells uncontrollably, and the cells do not die when they are supposed to. Substances in garlic may play a role in improving the process of cancer cell growth, including repairing DNA.

For example, a 2019 study supported the role of garlic in DNA repair and prevention of cancer cell development in an experimental lab setting.

Garlic and Cancer Treatment

There is currently research looking at the potential role of garlic in cancer treatment. Most of the research is animal or laboratory research, although there are also human studies. While the research doesn't quite have clear answers, it is showing some promising results.

According to a 2019 study, garlic may affect signaling pathways in cancer growth in a number of ways, including:

  • Cell cycle arrest: Garlic appears to cause cell cycle arrest, meaning it stops cells from continuing to divide. Cell cycle arrest is how many chemotherapy drugs work, in a variety of different points in the cell cycle.
  • Decreased blood vessel growth: Cancer cells need blood and nutrients to survive, and sometimes cancer cells can even grow their own blood vessels. Garlic appears to reduce the ability of cancer cells to promote the growth of new blood vessels.
  • Increased cell death: Normal cells die at a certain point, and cancer cells are often able to avoid this natural cycle of cell death. Garlic and its components appear to increase the rate of cancer cell death.

Few studies have been performed on the potential role of garlic treatment in humans, though a 2019 study was encouraging. Gastric cancer is very common worldwide, being the leading cancer diagnosis in some countries. A 2019 study in China found that treating Helicobacter pylori ( H. pylori, a bacterial infection associated with stomach cancer) for two weeks or giving garlic supplementation for seven years significantly reduced the risk of death due to gastric cancer.

How to Use and Buy Garlic for Health

You can use garlic in several ways to boost your health. If you want to reap the most rewards of garlic, it's helpful to understand the best ways to buy, prepare, and cook the cloves.

The greatest benefit will come from fresh, uncooked garlic. If you prefer to try other forms of garlic, there's garlic essential oil, garlic powder, and garlic extract, but the benefits of these products are not known.

How Much Garlic Should You Eat?

It may take only a small amount of garlic to provide its cancer-reducing effects. Even one clove of garlic daily has been linked with a reduced risk of some cancers.

Preparing and Purchasing Garlic

Preparing fresh garlic is ideal. Though jars of minced garlic are convenient and tasty, only a small fraction of the phytonutrients survive over time. Allicin is released when garlic is exposed to air, so it's important to chop or use your garlic press and then allow the garlic to sit exposed to air for around 10 minutes before adding it to a salad or using it in cooking.

When buying fresh garlic, consider the following:

Good Garlic Bad Garlic
Solid, firm heads Hollow or soft heads
Even color of outer skins Mottled outer skins (mold)
Head has weight Head is lightweight
Cloves are plump Cloves are shriveled
No green sprouts or leaves Green sprouts or leaves

Cooking With Garlic

It appears that microwave cooking can break down most of the healthy parts of this vegetable. Better options can include lightly sautéing, steaming, or baking.

What If You Don't Like Garlic?

Some people simply don't like garlic, but there are options that provide similar benefits.

Other foods that contain cancer-fighting allicin include:

  • Chives
  • Onions
  • Green onions
  • Scallions
  • Leeks
  • Shallots

Concerns About Supplementary Garlic

Two 2019 studies raised concerns about antioxidant supplements and cancer.

  • In one study, postmenopausal women who took antioxidants during chemotherapy and radiation for breast cancer were more likely to die.
  • In another study, treating lung cancer cells in the lab with antioxidant supplements appeared to promote the spread of the cancer cells.

It's important to note that these studies looked at antioxidant supplements, not dietary sources. Supplements may contain very high levels of the compounds, significantly more than would naturally be eaten. It is always important to discuss any supplements you're taking with your cancer care team.

Cancer Prevention Lifestyle

While there is some good evidence that garlic may lower cancer risk, using garlic alone isn't enough to prevent it entirely. Nutrition experts recommend combining garlic with other vegetables, fruits, dietary fiber, and regular exercise to improve your prevention strategies.

Summary

Garlic contains compounds that can benefit your health, including possibly reducing the risk of cancer. The compounds in garlic are more abundant when garlic is eaten raw, or lightly cooked, to prevent these protective compounds from breaking down.

This is just one step that can be taken when following a diet and living a healthy lifestyle with the goal of reducing the risk of cancer.

A Word From Verywell

Eating garlic can be an easy way to introduce some health-protective compounds into your diet. It can be included in an overall healthy lifestyle along with lots of fresh fruits and vegetables, and with regular exercise. To avoid adverse interactions with medications you take, never take any supplements without discussing with your healthcare team first.

Frequently Asked Questions

  • Does garlic powder have health benefits?

    Garlic has many health benefits. It can be good for the heart by lowering cholesterol, and it has antioxidant, antibacterial, and antiviral properties. Certain compounds in garlic may help reduce the risk of cancer. Garlic powder might contain the same beneficial compounds as raw garlic, but likely to a lesser extent.

  • Is there a certain way to cook garlic for health benefits?

    Yes. Eating garlic as close to its raw state as possible may give the best health benefits. Cooking garlic at very high heat, such as in a microwave, can possibly destroy the beneficial compounds in the garlic.

  • Who shouldn’t eat garlic daily?

    You shouldn't eat too much garlic or take garlic supplements if you are on blood-thinning medications. The combination could increase your risk of bleeding. People taking certain medications to treat HIV (human immunodeficiency virus) should avoid using too much garlic, as it interferes with how the medication works.

  • How much garlic should I eat in a day for cancer prevention?

    The exact amount of garlic needed is not known. However, it is suggested that one to two raw cloves of garlic daily can provide health benefits.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Almatroodi, S., Alsahali, M., Amatroudi, A., and A. Rahmani. Garlic and its Active Compounds: A Potential Candidate in The Prevention of Cancer by Modulating Various Cell Signalling Pathways. Anticancer Agents in Medicinal Chemistry. 2019. doi:10.2174/1871520619666190409100955

  3. Jung, A., Cai, X., Thoene, K. et al. Antioxidant Supplementation and Breast Cancer Prognosis in Postmenopausal Women Undergoing Chemotherapy and Radiation TherapyThe American Journal of Clinical Nutrition. 2019. 109(1):69-78. doi:10.1093/ajcn/nqy223

  4. Melguizo-Rodríguez L, García-Recio E, Ruiz C, De Luna-Bertos E, Illescas-Montes R, Costela-Ruiz VJ. Biological properties and therapeutic applications of garlic and its components. Food Funct. 2022 Mar 7;13(5):2415-2426. doi:10.1039/d1fo03180e

  5. Nicastro, H., Ross, S., and J. Milner. Garlic and onions: Their cancer prevention propertiesCancer Prevention Research. 2015. 8(3):181-189

  6. Petrovic V, Nepal A, Olaisen C, et al. Anti-cancer potential of homemade fresh garlic extract is related to increased endoplasmic reticulum stressNutrients. 2018;10(4):450.

  7. National Cancer Institute. Stomach cancer prevention

  8. Lignitto L, LeBoeuf SE, Hamer H, et al. Nrf2 Activation Promotes Lung Cancer Metastasis by Inhibiting the Degradation of Bach1Cell. 2019. doi: 10.1016/j.cell.2019.06.003

  9. National Center for Complimentary and Integrative Health. Garlic.

  10. Tattelman E. Health effects of garlicAFP. 2005;72(1):103-106.

Additional Reading

By Julie Scott, MSN, ANP-BC, AOCNP
Julie is an Adult Nurse Practitioner with oncology certification and a healthcare freelance writer with an interest in educating patients and the healthcare community.

Originally written by
Pam Stephan
Pam Stephan is a breast cancer survivor.
Learn about our editorial process