Onions and Garlic- Do they help Prevent Cancer?

Vegetables in the allium family, such as onions, garlic, leeks, and shallots, are a rich source of phytonutrients, and are used for the prevention and treatment of several diseases, including coronary heart disease, obesity, type 2 diabetes, gastrointestinal problems, and cancer.

There is evidence that allium vegetables can protect against cancers including stomach and colorectal cancer. Organic compounds containing sulphur, which give these vegetables their foul odor, may be responsible for the cancer-preventative effects. As well, it has been proposed that allium vegetables may kill and alter some tumor cell lines. A literature review in Environmental Health Perspectives reported that out of 37 case-control or cohort studies reviewed, 28 found some evidence that allium vegetables have protective effects against cancer, the strongest evidence being for stomach and colon cancers (Bianchini and Vainio, 2001). In addition, researchers from Cornell University found that the top five varieties of onions for protecting against cancer were Shallots, followed by Western Yellow, New York Bold, Northern Red, and Mexico (Yang et al., 2004)

Much of the research to date suggests that allium vegetables show promise for cancer prevention. However, there are several factors that need to be taken into account before recommending allium vegetables for cancer prevention, such as the stability of the cancer-preventative compounds when heated during cooking, and taking into account the intake of other fruits and vegetables which may also have cancer preventative effects (Bianchini and Vainio, 2001).

References

Bianchini and Vainio (2001). Allium vegetables and organosulfur compounds: do they help prevent cancer? Environmental Health Perspectives; 109(9):893-902.

Yang et al. (2004). Varietal differences in phenolic content and antioxidant and antiproliferative activities of onions. J Agric Food Chem; 52(22):6787-93.