Garlic consumption may reduce the risk of developing several types of cancer, as preliminary studies suggest, however the amount needed to lower the risk remains unknown because the studies evaluated different types and varying amount of garlic.
Garlic is considered by the AICR (American Institute for Cancer Research) to be one of their cancer fighting foods. The allium food family (including garlic, onions, leeks and chives) protect against stomach cancer. Their research also suggests that components of garlic have the ability to slow or stop the growth of tumours in breast, bladder, prostate, colon and stomach tissue as well as also the development of cancer in several stages and at various body sites.
Doctors from Department of Urology, China-Japan Friendship Hospital, Beijing, China reported that intake of allium vegetables (especially garlic) are related to lowering the risk of prostate cancer. This wonderful finding in reference to studies conducted up to May 2013 was published in Asian Pacific Journal of Cancer Prevention.
Next to China-Japan Friendship Hospital’s and AIRC’s, several other studies also indicate an association between reduced risks of certain cancers and increased intake of garlic.
EPIC, The European Prospective Investigation into Cancer and Nutrition, investigates connection between nutrition and development of cancers. (1) This ongoing study indicates that increased intake of garlic and onion can be associated with reducing risk of intestinal cancer. (2)
A large prospective study, The Iowa Women’s Study, investigating distribution of body fat, diet, age and other risk factors, conducted a study which findings showed a strong association between consumption of garlic and risk of colon cancer. In fact women who consumed the highest amount of garlic had a 50% lower risk of cancer of the distal colon. (3)
Garlic consumption and cancer risk studies were conducted in several population studies in China. The reduced risk of oesophageal and stomach cancers as well as prostate cancer (50% risk reduction) were directly linked to the consumption of allium vegetables, especially garlic and onions. (4,5,6)
Another population-based study conducted in the San Francisco Bay area showed evidence suggesting that increased consumption of garlic may reduce pancreatic cancer risk. (7)
A case controlled study in France associated reduced risk of breast cancer in patients who consumed greater amount of fiber and alliums.(
However, despite all the studies which indicate that increased garlic intake can be connected to a drop in the risk of developing certain types of cancer, numerous randomized studies conducted in China & Japan did not show the same results. (8,9,10)
So does garlic prevent cancer or not?
It is very likely it does, but not necessarily directly and in the way we think about it.
The use of differing garlic produce, the quantities consumed, the accuracy of reporting and an inability to compare the studies make an overall and definitive conclusion about garlic and cancer prevention extremely difficult. It isn’t clear whether garlic in combination with other nutritional components or alone may have the greatest effect. Hundreds of garlic varieties as well as different cultivation styles dependent on a region does not make this task any easier.
More studies on different type of preparation and processing is also needed.
Having said that, garlic’s antibacterial properties and ability to block the formation of cancer promoting substances, ability to enhance repair of DNA and reduce cell proliferation do promote the protective effect of garlic.
- Garlic and cancer: A critical review of the epidemiologic literature.Journal of Nutrition2001; 131(3s):1032S–1040S – Fleischauer AT, Arab L
- 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 Cancer2006; 118(10): 2559–2566 – Gonzalez CA, Pera G, Agudo A
- Vegetables, fruit, and colon cancer in the Iowa Women’s Health Study. American Journal of Epidemiology1994; 139(1):1–15. – Steinmetz KA, Kushi LH, Bostick RM, Folsom AR, Potter JD
- Protective effect of allium vegetables against both esophageal and stomach cancer: A simultaneous case-referent study of a high-epidemic area in Jiangsu Province, China. Japanese Journal of Cancer Research1999; 90(6):614–621. – Gao CM, Takezaki T, Ding JH, Li MS, Tajima K
- Allium vegetables and stomach cancer risk in China. Asian Pacific Journal of Cancer Prevention2005; 6(3):387–395. – Setiawan VW, Yu GP, Lu QY
- Allium vegetables and risk of prostate cancer: A population-based study. Journal of the National Cancer Institute2002; 94(21):1648–1651. – Hsing AW, Chokkalingam AP, Gao YT
- Vegetable and fruit intake and pancreatic cancer in a population-based case-control study in the San Francisco bay area. Cancer Epidemiology Biomarkers & Prevention2005; 14(9):2093–2097. – Chan JM, Wang F, Holly EA.
- An intervention study to prevent gastric cancer by micro-selenium and large dose of allitridum. Chinese Medical Journal (English)2004; 117(8):1155–1160 – Li H, Li HQ, Wang Y
- Randomized double-blind factorial trial of three treatments to reduce the prevalence of precancerous gastric lesions. Journal of the National Cancer Institute2006; 98(14):974–983. – You WC, Brown LM, Zhang L
- Effects of aged garlic extract (AGE) on colorectal adenomas: A double-blinded study. Hiroshima Journal of Medical Sciences2004; 53(3–4):39–45. – Tanaka S, Haruma K, Kunihiro M
National Cancer Institute is the source of the above information and related references.