Garlic and Cancer

Garlic and Cancer

Hasn’t you grandmother tell you when you were sick to eat fresh cut garlic with bread and butter?  Followed by warm milk with honey? This used to be one of the main recipes in my family when flu season arrived.

So, is garlic so magical? Let’s try to find out.

There are many claims that garlic and garlic supplements can prevent or cure cancer.

Garlic (allium sativum) is closely related to onions, leeks, shallots, scallions and chives. Extracts from garlic have been used as herbal remedies for centuries.

There is some evidence in population studies to suggest that garlic may reduce the risk of some cancers, but as of now this question is being actively studied in Prospective Phase III trails.

Based on NCI (National Cancer Institute) website - Some preliminary studies show that garlic consumption can reduce development of cancer, especially some gastrointestinal cancers.

European study EPIC, a prospective Investigation into Cancer and Nutrition is an ongoing multinational study of men and women from 10 different countries.

Its main goal is to investigate nutrition and cancer. In this study, preliminary data shows that higher intake of onion and garlic can reduce risk of gastrointestinal cancers. (1)

Data analysis from seven population studies showed that higher the amount of raw and cooked garlic consumed the lower the risk of stomach cancer. (3)

Iowa Women’s Health study showed women who consumed higher amount of garlic had 50% reduction of colon cancer to women that did not. (4)

In China stomach cancer is on rise and its association is to certain foods and preparation of food. Their population study showed the consumption of allium vegetables, especially onion, and garlic was lined to reduced risk of stomach cancer. (5)

Another study in China showed reduced prostate cancer risk by eating higher amount of garlic (6). In France, decrease risk of breast cancer was seen (7) and small study in US showed decreased incidence of pancreatic cancer (8).


Do we know how Garlic compounds can prevent cancer?

Protective effects from garlic (allylic compounds) may arise from:

  • its antibacterial properties (9)
  • its ability to block the formation of cancer-causing substances (10),
  • its ability to halt the activation of cancer-causing substances (11),
  • enhanced DNA repair (12),
  • reducing cell proliferation, or inducing cell death.(13)

But there are problems with some studies and data.

  1. Accuracy of reporting in the studies is difficult to be standardized.
  2. Amount of garlic consumed is unknown and it’s unclear if garlic alone or in combinations with other nutritional components may affect and provide the greatest benefit.
  3. What form of garlic should be used? Raw, cooked or in supplement, which form have the most protective effects? 

All of those questions are valid and more studies are needed to answer them.

There have been claims that garlic has immune – boosting properties that may reduce cancer cell growth and help the body to fight of diseases such as cold and flu. Those claims are currently under study.  We partially understand the mechanism of immune protection.

The few human studies that have looked at garlic supplements have not found them to be helpful against cancer.

There are many questions that remain to be answered.

There is considerable debate as to which preparations and amount of garlic could influence health. Cooking can reduce potency of garlic active ingredients. It maybe is best to simply mince garlic and eat it raw or add garlic to foods in end of cooking.

We don’t know how much garlic we should eat to have the protective affect. There are problems with eating too much garlic, it can lead to stomach irritation, causing stomach pain, increased gas and even vomiting. Garlic is also a natural blood thinner; it can increase risk of bleeding. Therefore high doses of garlic should never be given or used before any surgery.

Garlic also inhibits some enzymes in the liver, which can reduce effect of some drugs or even chemotherapy, therefore you need to always disclose to you family doctor or other physicians what you take.

We cannot say that eating high amount of garlic or taking garlic supplements will prevent cancer.

That said, we do recommend including garlic as a part of balanced diet (unless one has a particular health problem or is taking medication that has been shown to be adversely affected by garlic)

I would recommend using raw or cooked garlic for benefits and not take a garlic supplement since most likely the benefit of garlic is a combination effect of verity compounds found in garlic. The supplements are newer versions and the active ingredients are hard to measure in such substances. Garlic supplements have not been shown to have any health benefits, and they might even be dangerous. I don’t recommend using garlic “supplements” for cancer prevention.

The fresh and natural is the way to go!


  1. Gonzalez CA, Pera G, Agudo A, et al. Fruit and vegetable intake and the risk of stomach and oesophagus adenocarcinoma in the European Prospective Investigation into Cancer and Nutrition (EPIC-EURGAST). International Journal of Cancer 2006; 118(10): 2559–2566.
  2. Steinmetz KA, Kushi LH, Bostick RM, Folsom AR, Potter JD. Vegetables, fruit, and colon cancer in the Iowa Women’s Health Study. American Journal of Epidemiology 1994; 139(1):1–15.
  3. Fleischauer AT, Arab L. Garlic and cancer: A critical review of the epidemiologic literature. Journal of Nutrition 2001; 131(3s):1032S–1040S.
  4. Steinmetz KA, Kushi LH, Bostick RM, Folsom AR, Potter JD. Vegetables, fruit, and colon cancer in the Iowa Women’s Health Study. American Journal of Epidemiology 1994; 139(1):1–15.
  5. Setiawan VW, Yu GP, Lu QY, et al. Allium vegetables and stomach cancer risk in China. Asian Pacific Journal of Cancer Prevention 2005; 6(3):387–395.
  6.  Hsing AW, Chokkalingam AP, Gao YT, et al. Allium vegetables and risk of prostate cancer: A population-based study. Journal of the National Cancer Institute 2002; 94(21):1648–1651.
  7. Challier B, Perarnau JM, Viel JF. Garlic, onion and cereal fibre as protective factors for breast cancer: A French case-control study. European Journal of Epidemiology 1998; 14(8):737–747
  8. Chan JM, Wang F, Holly EA. Vegetable and fruit intake and pancreatic cancer in a population-based case-control study in the San Francisco bay area. Cancer Epidemiology Biomarkers & Prevention 2005; 14(9):2093–2097.
  9. Ruddock PS, Liao M, Foster BC, et al. Garlic natural health products exhibit variable constituent levels and antimicrobial activity against Neisseria gonorrhoeae, Staphylococcus aureus and Enterococcus faecalis. Phytotherapy Research 2005; 19(4):327–334.
  10. Shenoy NR, Choughuley AS. Inhibitory effect of diet related sulphydryl compounds on the formation of carcinogenic nitrosamines. Cancer Letters 1992; 65(3):227–232.
  11. Milner JA. Mechanisms by which garlic and allyl sulfur compounds suppress carcinogen bioactivation. Garlic and carcinogenesis. Advances in Experimental Medicine and Biology 2001; 492:69–81.
  12. L'vova GN, Zasukhina GD. Modification of repair DNA synthesis in mutagen-treated human fibroblasts during adaptive response and the antimutagenic effect of garlic extract. Genetika 2002; 38(3):306–309.
  13. Boon H, Wong J. Botanical medicine and cancer: A review of the safety and efficacy. Expert Opinion on Pharmacotherapy 2004; 5(12):2485–2501.