The relationship between the index of nutritional quality and the risk of colorectal cancer and adenoma : a case-control study.

Objective: Colorectal cancer is one of the most common cancers in the world, whereas dietary factors are its most modifiable risk factors. The index of nutritional quality is considered as a general overview of the nutrient content of diet. The aim of this study is to determine the relationship between the index of nutritional quality and the risk of colorectal cancer and adenomas. Methods: Overall, 129 colorectal cancer and 130 colorectal adenoma cases and 240 healthy controls were studied in three major general hospitals in Tehran province, Iran. Index of nutritional quality scores were calculated based on information on the usual diet that was assessed by a valid and reliable Food Frequency Questionnaire. Multivariate logistic regression was used to estimate the relationship between the index of nutritional quality scores and the risk of colorectal cancer and adenoma. Results: After controlling for several confounding factors, the index of nutritional quality of calcium, vitamin C, riboflavin, folate and fiber were associated with decreased risk of colorectal cancer [ORcalcium: 0.21 (0.08-0.52), ORvitC: 0.16 (0.09-0.28), ORvitB2: 0.35 (0.18-0.65), ORfolate: 0.33 (0.16-0.65), ORfiber: 0.35 (0.21-0.58)]. Also, the inverse association were observed between risk of CRA and the index of nutritional quality of calcium, vitamin C, riboflavin, folate and fiber [OR (calcium): 0.32 (0.14-0.74), ORvitC: 0.51 (0.34-0.73), ORvitB2: 0.48 (0.28-0.82), OR (folate): 0.44 (0.23-0.81), OR (fiber): 0.62 (0.42-0.92)]. Conclusion: This study showed that individuals who have a healthier diet, high in calcium, vitamin C, riboflavin, folate and fiber and food groups like fruits, vegetables and whole-grain and less in sweets and red or process meats are at a lower risk of colorectal cancer and CRA than those with unhealthy and poor diet.