# Adherence to the diet with higher protein quality reduces the risk of colorectal cancer: results from a population-based prospective study

## TL;DR

A study of over 100,000 Americans found that higher-quality protein diets are linked to lower colorectal cancer risk and mortality.

## Contribution

This is the first large-scale US study to show that protein quality, not just quantity, affects colorectal cancer risk.

## Key findings

- Higher protein quality index (HPPQI) was linked to 23% lower CRC incidence and 34% lower mortality.
- Sensitivity analyses confirmed the robustness of these associations.
- No significant associations were found for specific cancer subtypes (proximal, distal, rectal).

## Abstract

Protein quantity’s link to colorectal cancer (CRC) risk is known, but protein quality’s impact on US populations remains unclear. This study fills the gap via a population - based prospective study of 101,709 American adults from the PLCO Cancer Screening Trial.

From 154,887 adults aged 55–74 years at 10 US screening centers, we formed the study group. HPPQI was calculated from the DHQ. Cox regression analysis determined HRs and 95% CIs for HPPQI - CRC associations. Subgroup and sensitivity analyses identified modifiers and ensured robustness.

During the study period, 1100 CRC cases and 314 CRC-related deaths were documented. In our result, HPPQI was significantly negatively associated with incidence of CRC (HR Q4 vs. Q1: 0.77; 95% CI: 0.65, 0.93; P = 0.009 for trend), as well as mortality rate (HR Q4 vs. Q1: 0.66; 95% CI: 0.47, 0.91; P = 0.024 for trend). The relationships between HPPQI and the incidence and mortality of CRC were robustly supported by sensitivity analyses. Nevertheless, upon separate examination of the relationships between HPPQI and proximal colon cancer, distal colon cancer, and rectal cancer, none of these associations attained statistical significance (all P-values > 0.05).

Our findings suggest focusing on higher quality of protein consumption may be an effective approach to reduce the risk of CRC in the US population.