Garlic and onion intake helps to prevent head and neck cancer

Head and neck cancer (HNC) is the sixth most common cancer in the world. The major recognized risk factors for HNC are tobacco and alcohol, with 5–10-fold higher risks for smokers as compared with nonsmokers and for heavy drinkers as compared with abstainers or moderate drinkers. Only a few studies analyzed the role of allium vegetables with reference to HNC, with mixed results. 

A scientific consortium of 22 international health institutes investigated the potential beneficial role of garlic and onion within the International Head and Neck Cancer Epidemiology (INHANCE) Consortium.

Full study is available online since July 2nd 2015 at:
http://onlinelibrary.wiley.com/doi/10.1002/mnfr.201500042/pdf

For the survey, scientists analyzed pooled individual-level data from eight case-control studies, including 4590 cases and 7082 controls. Five studies were conducted in Europe (65% of total cases and 75% of controls), two in North America (27% of total cases and 17% of controls) and one in Central America (8% of total cases and 8% of controls). Four studies were hospital-based and four were population-based studies.

The results of this pooled-analysis support a possible moderate inverse association between garlic and onion intake and HNC risk. The distribution of HNC cases and controls according to selected variables (age, gender, race/ethnicity, education cigarette smoking and alcohol drinking) showed that 81% of HNC cases were men and 95% were non-Hispanic whites. Patients with HNC were more frequently tobacco users and alcohol drinkers.

Results showed an inverse relation between garlic consumption and HNC risk. The pattern of risk was similar for onion, though the inverse association was significant for larynx only. In particular, high garlic use was associated with a significant risk reduction of overall HNC and oro/hypopharyngeal cancers by 26 and 38%, respectively. Further, consuming more than three portions of onion per week was associated with a significant reduction of laryngeal cancer risk by more than 30%.

Scientists explain that the inverse association between allium vegetables and the risk of HNC may be related to various components of garlic and onion. Allium vegetables contain many chemicals with potential antioxidant and anticancer activity, including organosulfur compounds, flavonoids, minerals and vitamins. In particular, garlic contains around 33 sulfur compounds, while onions contain several sulfoxides, mainly S-propenylcysteine sulfoxide, S-propylcysteine sulfoxide and S-methylcysteine sulfoxide

Scientists conclude, although the most effective strategy for HNC prevention involves alcohol and tobacco control, selected dietary advices, including a vegetables rich diet, specifically with a high allium vegetables intake, may reduce the occurrence of this neoplasm with high incidence and low survival.

Source: Carlotta Galeone et al., ‘Relation of allium vegetables intake with head and neck cancers: Evidence from the INHANCE consortium’, 2015, Molecular Nutrition and Food Research, Vol. 59, pages 1641–1650.