Does Garlic Reduce Your Risk of Cancer?

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

Garlic is thought to have cancer prevention properties related to its antibacterial and antioxidant effects in the body, and population studies suggest this theory is true. Some studies have shown benefits with garlic in relation to cancers of the stomach, colon, esophagus, pancreas, breast, and prostate, but the magnitude of cancer risk reduction is still unclear, and different epidemiological studies have been reporting conflicting results.. Components of garlic such as allicin, flavonoids, and allyl sulfides all contribute to different mechanisms that reduce risk. There is also some preliminary evidence that garlic might play a role in cancer treamtent as well. That said, understanding how to purchase, prepare, and cook garlic is important lest you lose those important phytonutrients between the grocery store and your plate.

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Garlic Basics

Garlic and onions have been a part of cooking since the days of ancient Greece and Rome. The fragrant garlic plant has been called by many names, including "the bulb of the tree of life" (for its anti-aging properties) and "the stinking rose" (even though it is related to lilies and not roses).

Garlic has been credited with the power to enhance your sex life, give endurance to athletes, and ward off vampires. But, more importantly, the health benefits of garlic include its natural antibiotic and antioxidant properties, both of which may help prevent cancer.

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

You'll know where the garlic is planted long before you see it, as its strong, sulfuric fragrance will declare its location very distinctly. Although dining on garlic-flavored foods may give you "garlic breath," doing so can improve your health by lowering high blood pressure and bad cholesterol.

Health Benefits

When looking at potential benefits of foods in relation to cancer prevention, it's helpful to look both at population studies (do people who eat a large amount of the food have a lower rate of cancer?) and the possible mechanism by which they work (does the biological mechanism fit?)

Cancer Reduction/Prevention

It's certainly not possible to prevent all cancers, but population studies have found a reduced risk of the following cancers in people who consume more garlic:

  • Stomach cancer
  • Colon cancer
  • Pancreatic cancer
  • Esophageal cancer
  • Breast cancer
  • Prostate cancer

Anti-Cancer Compounds

Garlic has natural antioxidants and is anti-inflammatory, antibacterial, and antiviral. The knobs and cloves of garlic contain high levels of sulfur, flavonoids, and selenium. And, when it is crushed, chopped, or bruised, garlic produces the compound allicin.

It is garlic's antibacterial properties that may help to prevent cancer as well as its ability to enhance genetic repair, slow down cell proliferation, and prevent the formation of carcinogenic substances in the body.

Three of the cancer-fighting compounds in garlic include:

  • Allicin: A powerful plant compound that is antibiotic and anti-fungal. This substance is strong enough to cause blisters if you get too much on your skin, but allicin fades quickly after it is produced. Cooking speeds the breakdown of allicin, and microwave cooking appears to kill it and destroy the health benefits.
  • Flavonoids: Aromatic plant compounds that are considered to have antioxidant and anti-inflammatory properties. These compounds fight cancer by preventing cell damage.
  • Selenium and allyl sulfides: Both of these plant chemicals may be anti-mutagens, or substances that prevent cancer by blocking damage to cells' DNA or stimulating the body to repair damaged DNA.

How Garlic May Reduce the Development of Cancer

There are several mechanisms by which garlic may inhibit the development of cancer. There are additional mechanisms by which it may also slow the cell cycle in cancer cells already present or induce apoptosis (cell death). Examples of just a few of these are discussed here.

DNA Repair

Garlic's ability to enhance genetic repair, in particular, is worth noting. Cancer begins when a series of mutations (damage to DNA in cells) leads to a cell grows out of control (a cancer cell) and becomes a cancerous tumor.

Damage to DNA in genes in the human body is common, caused by both environmental carcinogens and the products of normal metabolism in the body. Even when substantial damage occurs, however, the body has a way to either repair the damaged DNA or eliminate un-ixable damaged cells. Tumor suppressor genes are genes we all have that carry the blueprint for proteins that do these jobs. When these genes are mutated, a person may have an increased risk of developing cancer (a genetic susceptibility). BRCA gene mutations are an example of mutated tumor suppressor genes.

Cancer is common, affecting one in two men and one in three woman during a lifetime (not including skin cancer). While we are familiar with some of the causes and can thus avoid them, there is much that we don't understand. Therefore, a dietary compound that enhances DNA repair when damage occurs is exciting.

A 2019 study further supported the role of garlic in DNA repair in that (at least in the lab) garlic appeared to enhance the expression of tumor suppressor genes.

Inhibition of Carcinogens Such as Nitrosamines

Just as dietary components may lower cancer risk, there are some that increase risk as well. Both nitrosamines and heterocyclic amines fall into this category. Heterocyclic amines are one of the reasons that grilled meat is associated with an increased risk of developing cancer. The grilling process itself, and exposure to heat alone can result in these carcinogens being formed. (Grilling vegetables does not result in heterocyclic amines). Garlic appears to inhibit the formation of both heterocyclic amines and nitrosamines in grilled food.

Adding a little garlic to your meats before grilling might help, but there are other ways to reduce carcinogens in grilled foods, such as marinating meats for 20 minutes before cooking, cooking at lower temperatures, and using the right charcoal.

Garlic and Cancer Treatment

There is currently research looking at the potential role of garlic in cancer treatment. While the research is still in its infancy, and we don't know whether studies done in the lab can translate into actions in the human body, it doesn't necessarily matter if you are using garlic to enhance the taste of the foods you eat. According to a 2019 study, garlic may affect signaling pathways in cancer growth in a number of ways.

  • Cell cycle arrest: Garlic appears to cause cell cycle arrest in the G0/G1 phase as well as the G2/M phase. Cell cycle arrest is how many chemotherapy drugs work, though at different points in the cell cycle.
  • Decreased angiogenesis: Angiogenesis, or the growth of new blood vessels is necessary for tumors to grow. In fact, it's thought that tumors cannot grow beyond a few millimeters in size without angiogenesis. Garlic appears to reduce the ability of cancer cells to promote the growth of new blood vessels.
  • Increased apoptosis: Normal cells die (apoptosis) at a certain point, while cancer cells are often able to avoid this programmed cell death. Garlic and its components appeared to increase the rate of apoptosis of cancer cells.

Garlic and Cancer Survival

Few studies have been performed looking at 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 both H. pylori treatment (the bacterial infections associated with stomach cancer) for two weeks or garlic supplementation for seven years were associated with a significantly reduced risk of death due to gastric cancer.

Garlic and Cancer Cachexia

Cancer cachexia, a syndrome that includes both unintentional weight loss and muscle loss (atrophy), is thought to be directly responsible for roughly 20% of cancer-related deaths. To date, the prevention and treatment of cachexia has been challenging, and supplementation of calories alone is inadequate.

A component of crushed garlic, A-ajoene, has intrigued researchers as a potential therapy in reducing cancer cachexia. A 2019 study looked at the effects of an ajoene extract both in mice and in human cancer cells grown in the lab. It was found that ajoene may function in two separate ways both to reduce the inflammatory responses that contribute to muscle atrophy and by actually promoting muscle protein synthesis. It's not yet known if these results will mean that ajoene (a sulfur compound present in crushed garlic) can protect against muscle atrophy in people with cancer, but garlic may help in yet another way. A lack of appetite is far too common with cancer, especially advanced cancer, and garlic can spice up a meal to make it more appetizing.

Dietary vs. Supplementary Garlic

Two 2019 studies raised concern about antioxidant supplements in people living with cancer. In one study, postmenopausal women who took antioxidants during chemotherapy and radiation for breast cancer were more likely to die.

In other study, treating lung cancer cells in the lab with antioxidant supplements appeared to promote the spread (metastasis) of the cells.

It's important to note that these studies looked at antioxidant supplements, not dietary sources. most oncologists believe that dietary antioxidants are safe, and even encourage these foods during cancer treatment.

How to Use and Buy Garlic for Health

You can use garlic in several ways to boost your health, but the greatest benefit will come from fresh, uncooked garlic. If you prefer to try other forms of garlic, there's garlic essential oil, garlic oil macerate, garlic powder, and garlic extract, but the benefits of these products isn't certain.

If you want to receive the benefits of garlic in your diet, it's important to not only find garlic in the store, but understand the best ways to buy, prepare, and cook the cloves.

How Much Garlic Should You Eat?

Unlike some studies looking at cancer prevention and foods, it may only take a small amount of garlic to receive its cancer reduction effects. Even one clove of garlic daily has been linked with a reduced risk of some cancers.

To Supplement or Not

Garlic supplements are also available if you want to avoid "garlic breath." However, be warned that the allicin contained in these supplements varies greatly and will be much less powerful than that which is released from a fresh garlic clove. In general and when at all possible, it's best to eat foods rather than take supplements to get your phytonutrients. This is especially true for those who are currently living with cancer.

Preparing and Purchasing Garlic

Preparing fresh garlic is ideal. Though pre-minsed jars of 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

After buying and preparing good garlic, it's important to not destroy the benefits. It appears that microwave cooking does just that, with most of the healthy phytonutrients being destroyed. Better options can include lightly sauteing, steaming, or baking.

What if You Don't Like Garlic?

Some people simply don't like garlic, but there are still options for getting the benefits. Other allium foods (those that contain cancer-fighting allicin) include chives, onions, green onions, scallions (immature onions), leeks, and shallots.

Garlic is Only One Component of a Cancer Prevention Diet/Lifestyle

While there seems to be at least some good evidence that garlic may lower cancer risk, using garlic alone is reminiscent of fad diets that fail. Experts in nutrition recommend eating a "rainbow of foods" to ensure you get a variety of healthy phytonutrients. Combine garlic with cruciferous vegetables, fruits, dietary fiber, and regular exercise to maximize your health and prevention strategies.

How you eat may also play a role in cancer and cancer prevention. Intermittent fasting, or prolonged nighttime fasting (eating for roughly 8 hours each day and fasting for around 16 hours). Not only has intermittent fasting been linked with a lower risk of breast cancer recurrence, but a 2019 review in the New England Journal of Medicine provides evidence that suggests most people might benefit from this style of eating with regard to not only the avoidance of disease and reduction in obesity, but from the standpoint of overall longevity.

A Word From Verywell

You don't have to chew on one clove of garlic a day by itself to get the anticancer benefits from this fragrant bulb. Just chop or finely dice garlic and sprinkle it on a salad, a thick slice of bread, over a fish fillet, or on your cooked vegetables. And if you notice that vampires avoid you, your daily jog gets easier and your sex life improves, well, that's good too.

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6 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. Li WQ, Zhang JY, Ma JL, et al. Effects of Helicobacter pylori treatment and vitamin and garlic supplementation on gastric cancer incidence and mortality: follow-up of a randomized intervention trial. BMJ. 2019. 366:l5016. doi:10.1136/bmj.l5016

  3. Lee H, Heo JW, Kim AR, et al. Z-ajoene from Crushed Garlic Alleviates Cancer-Induced Skeletal Muscle Atrophy. Nutrients. 2019. 11(11). pii: E2724. doi:10.3390/nu11112724

  4. 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

  5. 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

  6. de Cabo R, Mattson MP. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine. 2019. 381(26):2541-2551. doi:10.1056/NEJMra1905136

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