Low-Carbohydrate Diet Score and the Risk of Colorectal Cancer: Findings from the Singapore Chinese Health Study

Background: Colorectal cancer is common cancer with a high mortality rate. Low-carbohydrate diet (LCD) score holistically evaluates the LCD pattern from carbohydrate, protein, and fat intake. Epidemiologic data of LCD–colorectal cancer association are sparse. Methods: We evaluated the associations between LCD (i.e., total, animal- and plant-based) and colorectal cancer risk in the Singapore Chinese Health Study, a population-based prospective cohort study including 61,321 Chinese in Singapore who were 45 to 74 years old at baseline. Cox proportional hazard regression model was used to determine the HRs and respective 95% confidence intervals (CI) for colorectal cancer associated with LCD after adjusting for potential confounders, including age, sex, BMI, physical activity, family history of colorectal cancer, etc. Results: After an average of 19.5 years of follow-up, 2,520 participants developed colorectal cancer (1,608 colon cancer and 912 rectal cancer). Overall, the association between total or plant-based LCD scores with the risk of colorectal, colon, or rectal cancer was null (all P_trend ≥ 0.28). The animal-based LCD was modestly associated with colon cancer risk (P_trend = 0.02), but not with rectal cancer. Compared with the lowest quartile, HRs (95% CIs) of colon cancer for quartiles 2, 3, and 4 of animal-based LCD were 1.12 (0.98–1.29), 1.27 (1.10–1.46), and 1.14 (0.99–1.31), respectively. Conclusions: A low-level carbohydrate diet with a high level of animal protein and fat was associated with a moderate increase in the risk of colon cancer among Chinese Singaporeans. Impact: High consumption of animal protein/fat and low consumption of carbohydrates may increase colon cancer risk.