Cooking methods and esophageal squamous cell carcinoma in high-risk areas of Iran

Cooking methods have been implicated in the etiology of gastrointestinal cancers, reflecting exposure to potential carcinogens as results of cooking. We used a validated food frequency questionnaire and a pretested cooking method questionnaire in 3 groups: 40 esophageal squamous cell carcinoma (ESCC) cases from a high-risk area in northeast of Iran, 40 healthy subjects from the same high-risk area, and 40 healthy subjects from a low-risk area in Southern Iran. We compared the frequency of boiling, grilling, and frying, and the frying score among these 3 groups. We also calculated "frying index" by multiplying the frequency of each fried food item by its frying score. Mean frying to boiling ratios were 18.2:1, 12.8:1, and 2.6:1 for cases, high-risk controls, and low-risk controls, respectively (P < 0.01). Reuse of cooking oil for frying was reported in 37.5% of the ESCC cases, 25% of high-risk controls, and 7.5% of low-risk controls (P < 0.001). Frying index was higher in the high-risk than in the low-risk controls (P < 0.001) and in cases than in the high-risk controls (P < 0.05) after adjusting for smoking, opium use, rural residence, education, and ethnicity. High-temperature cooking and frying may be associated with increased risk of ESCC in high-risk areas.