Association of low-carbohydrate diet score and carbohydrate quality index with colorectal cancer risk: a large-scale case-control study.

Purpose: Carbohydrate intake has been linked to colorectal cancer (CRC) risk, with variations depending on the quantity and quality of carbohydrates consumed. This study aimed to investigate the association between carbohydrate quantity and quality, using the low-carbohydrate diet score (LCD) and carbohydrate quality index (CQI), and the risk of CRC in the Chinese population.

Methods: We conducted a case-control study in Guangzhou, China, with 2,799 CRC cases and an equal number of sex- and age-matched controls. Dietary data were collected using a validated food frequency questionnaire to derive the LCD and CQI, assessing the quantity and quality of carbohydrate intake separately. Odds ratios (OR) and 95% confidence interval (CI) for CRC risk were estimated using unconditional logistic regression models, and restricted cubic splines were used to explore potential non-linear relationships.

Results: The results demonstrated that higher adherence to the overall LCD score, plant-based LCD score, and CQI was associated with a lower risk of CRC. The adjusted ORs (95%CIs) for the highest quintile of intake in comparison with the lowest quintile were 0.76 (0.63, 0.91) for the overall LCD score, 0.61 (0.50, 0.74) for the plant-based LCD score, and 0.70 (0.58,0.84) for the CQI, respectively. However, the animal-based LCD did not show a significant association with CRC risk, with the adjusted OR (95%CI) for the highest quintile compared to the lowest being 0.98 (0.81, 1.18). Restricted cubic splines analysis showed non-linear associations of the overall LCD score, animal-based LCD score, and plant-based LCD score with CRC risk. In contrast, a linear relationship was observed between CQI and CRC risk (P_nonlinear = 0.594).

Conclusions: Our findings indicate that the overall LCD score, the plant-based LCD score, and the CQI were inversely associated with the risk of CRC.