Objective: To study multiple risk factors of N-nitroso compounds (NOC) in high- and low-risk areas for esophageal cancer in southern China.
Method: The samples of 24-hr diets and 12-hr overnight urine were collected from 120 male healthy subjects (35-64 years old) selected by a 3-stage random cluster sample procedure in each of the high-risk area (Nanao County) and low-risk area (Lufeng County) for esophageal cancer. The urinary samples were respectively collected from undosed subjects, subjects ingested 500 mg L-proline (together with 200 mg ascorbic acid ) and subjects ingested 500 mg proline. The levels of total NOC (TNOC), N-nitrosamino acids (NAAs), volatile N-nitroso compounds and reductive ascorbic acid (VC) in the samples were measured. By unconditional logistic stepwise regression model, we analyzed the association between the multiple factors of NOC and esophageal cancer mortality. The factors included the intake and excretion levels of various kinds of NOC, the ability of NAAs endogenous formation and its inhibition by VC, and nutrition status of VC in the body.
Results: The results of unconditional logistic stepwise regression showed that risk factors entered the model were diet TNOC content (OR 9.613, 95% CI 1.921-48.115) and urinary NAAs level after ingested VC (OR 1.137, 95 % CI 1.001-1.298).
Conclusion: The higher level of diet TNOC and the lower inhibition ability of NOC endogenous formation by VC were important risk factors on NOC etiology of esophageal cancer in southern China.