Eating Garlic Reduces Risk of Lung, Bowel Cancer By 40%.
It is not possible to make any overall conclusions about the anticancer properties of garlic due to the limitations of the existing studies.
Natural News carried an article entitled ‘Eating Garlic Daily Reduces Risk of Lung, Bowel Cancer by 40%’. The author recommends growing your own garlic using vertical gardening to avoid the risk of contamination from commercially grown garlic.
The article in Natural News quotes an overview of the health benefits of garlic which was published by the National Cancer Institute. The National Cancer fact sheet states that a number of population studies show an association between increased intake of garlic and reduced risk of a number of cancers, specifically cancer of the stomach, colon, esophagus, pancreas, and breast. However, the National Cancer Institute publication explains that population-based studies are limited and they cannot differentiate between association and causation. Populations studies can tell that two things happen together but not how these two things relate to each other.
The National Cancer Institute factsheet summarizes the current status of clinical trials looking at the health benefits of garlic. Only a handful of clinical trials have been done examining the potential anti-cancer benefits of garlic.
The factsheet quotes four randomized controlled trials on the anticancer effects of garlic: three of these studies relate to gastroinestinal carcinoma and one of which relates to skin cancer.
Of the three randomized clinical trials relating to gastric cancer, the first study compared garlic extract plus selenium versus placebo in 5000 Chinese men and women. The study found a 33% reduced risk of all tumors in the garlic plus selenium treatment arm. Specifically the risk of stomach cancer was reduced by 52% as compared to the control group (1).
The second study compared high dose [2.4 ml] versus low dose [0.16 ml] garlic extract in Japanese subjects with non-cancerous colorectal tumors. 67% of the low-dose group and 47% of the high-dose group developed new adenomas suggesting a possible beneficial effect of garlic (2).
However, studies from the third randomized control trial looking at precancerous lesions of the stomach, showed no beneficial effect of garlic supplementation at a dose of 800 mg a day (4).
The study relating to skin cancer showed beneficial effects of topical application of garlic extract but the study only involved a total of 21 subjects (3).
The National Cancer Institute concludes that the paucity of data and the limitations of available studies make it impossible to draw any overall conclusions about garlic and cancer prevention and recommend that well-designed human clinical trials are needed to answer this question.
The National Cancer also warned of potential side effects of garlic including life-threatening allergies, significant drug-drug interactions (particularly with antiretroviral drugs used for management of HIV and blood-thinning drugs).
They also recommend caution with home-grown garlic which is prone to the development of Clostridium botulinum.
In summary, eating garlic has not been proven to reduce the risk of any cancer.