Carbohydrate quality rather than quantity affects risk of colorectal cancer

1. In a large prospective cohort, consumption of higher quality carbohydrates was associated with a decreased risk of colorectal cancer compared to lower quality carbohydrate diets.

2. Lower carbohydrate quantity consumption was not associated with significant correlations in colorectal cancer risk or outcomes.

Evidence Rating: 1 (Excellent)

Colorectal cancer (CRC) confers a significant healthcare burden worldwide, and it has been well documented that individual CRC risk can be mediated through diet. In prior literature, both the quantity and quality of carbohydrate consumption has been postulated as potential mediators of CRC risk and outcomes, although this has not been well characterized. To further characterize this link, patients from the Prostate, Lung, Colorectal, and Ovarian (PLCO) Cancer Screening Trial, a large randomized clinical trial between 1993 and 2001, were followed over a mean follow-up of 8.8 years. They had both the quality and quantity of their carbohydrate consumption tracked, as measured by the carbohydrate quality index (CQI), and low-carbohydrate diet score (LCDs), respectively. CQI was calculated via a validated tool that assessed factors such as glycemic index, whole grain to total grain ratio, solid carbohydrate to total carbohydrate ratio, and dietary fiber. It was found that individuals in the highest quartiles of CQI had significant lower CRC incidence (HR 0.80 95% CI 0.67–0.96) and mortality (Q4 vs Q1: HR 0.61, 95% CI 0.44–0.86) when compared to those in the lowest quartiles, specifically for the distal colon and rectum. Interestingly, no associations were found between LCDs and CRC incidence or mortality in any CRC types. Study findings suggest that quality of carbohydrate intake, rather than quantity, has the effect on CRC incidence as well as mortality risk. With further research, practitioners and dietitians alike may utilize study findings to help counsel patients on their dietary choices to further mitigate CRC risk. 

Click to read the study in BMC Medicine

Image: PD

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