Chinese balanced diet quality and risk of upper gastrointestinal cancers: a population-based cohort study in China

Background: Upper gastrointestinal (UGI) cancers are highly prevalent in China and have been linked to dietary factors, yet the impact of overall diet quality remains underexplored. We aimed to investigate the association between Chinese diet quality, as measured by the Chinese Diet Balance Index 2016 (DBI-16) and plant-based diet index (PDI), and UGI cancer risks in high-risk populations. Methods: We conducted a prospective cohort study from 2017 to 2019 in five high-risk regions of China, involving 44,495 residents aged 40-69 years. Diet quality was evaluated using DBI-16, which includes higher bound scores (HBS), lower bound scores (LBS), and diet quality distance (DQD), alongside the PDI, which distinguishes between overall, healthy, and unhealthy plant-based diets. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression analysis. Findings: Over a median follow-up of 55 months, 790 cases of UGI cancer were recorded. The study revealed suboptimal dietary quality in these high-risk areas, marked by both excessive and inadequate food intake. A high HBS (excessive intake) was associated with a lower risk of UGI cancers (HR=0.57, 95% CI: 0.41-0.81) and esophageal cancer (HR=0.51, 95% CI: 0.32-0.80). Conversely, significant dietary imbalance (high DQD) was linked to an increased risk of UGI cancers (HR=1.59, 95% CI: 1.08-2.36), while severe inadequate intake (high LBS) was only associated with an increased risk of esophageal cancer (HR=2.16, 95% CI: 1.00-4.65). A higher overall PDI was protective against UGI cancers (HRQ4 vs. Q1=0.69, 95% CI: 0.49-0.98), whereas an unhealthy PDI increased the risk (HRQ4 vs. Q1=1.92, 95% CI: 1.38-2.67). Interpretation: This study highlights the importance of promoting balanced plant-based diets to reduce UGI cancer risks in high-risk Chinese populations. Further research should investigate the underlying mechanisms and evaluate the effectiveness of dietary interventions.