Can Allium vegetables prevent cancer?

The aim of this paper is to review the evidence for or against an association between regular consumption of Allium vegetables and cancer. A Medline search was conducted to identify all publications on the topic. Twenty epidemiological studies were found. The majority investigate the association of onion consumption and cancer, while eight studies assess garlic consumption. With only one exception, these studies suggest that Allium vegetables convey a protective effect, in particular from cancers of the gastrointestinal tract. These results could be due to an artefact but more likely, they are based on plausible biological mechanisms. Anti-bacterial or anti-mutagenic effects of Allium vegetables are prime candidates to explain this relationship. In conclusion, the hypothesis that regular consumption of Allium vegetables reduces the risk of cancer is compelling and would seem to deserve testing in intervention trials.