Dietary pattern and odds of lung cancer: a large case-control study in Iran.

Background: Lung cancer is known as the second main fatal cancer in the world. Besides smoking, the effect of other lifestyle factors, especially dietary habits, on the risk of this cancer has not been established yet. The current study is designed to assess the association between various dietary patterns and the odds of lung cancer in Iran.

Methods: This large case-control study was conducted on 608 cases and 3397 controls enrolled in the IROPICAN study in Iran. Dietary intakes were reported using a 171-item validated food frequency questionnaire. Data on the participants' dietary consumption and demographic characteristics was collected by performing face-to-face interviews. Factor analysis was carried out to extract the main nutritional patterns. Multi-model adjusted logistic regression was conducted to evaluate the association between extracted dietary patterns and the risk of lung cancer.

Results: Three dietary patterns were derived. Significantly higher odds of small cell carcinoma were observed with higher adherence to the "Pesco vegetarian" dietary pattern, rich in fruits, vegetables, legumes and nuts, olives and olive oil, honey, and fish (OR _{T3 vs. T1} = 1,81, 95% CI 1.05, 3.11, P = 0.04). We found no significant association between the odds of total or subtypes of lung cancer with the "animal and sugar" dietary pattern, full of red and processed meat, dairy, sugar, coffee, tea, and chicken, and the "carbohydrate, fat, and egg" dietary pattern, rich in grains, eggs, fat, coffee and tea, and salt, and poor in dairy and red meat.

Conclusion: While there was no association between dietary intake and the odds of lung cancer, adherence to the "pesco vegetarian dietary pattern" might be associated with an increase in the odds of small-cell carcinoma lung cancer.