Balanced diet quality and risk of upper gastrointestinal cancers: Insights from a prospective cohort study in China.

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. This study aimed to assess 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. We conducted a prospective cohort study from 2017 to 2019 in five high-risk regions of China. Diet quality was assessed using DBI-16 and PDI. 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 PDI. Hazard ratios (HRs) and 95% confidence intervals (CIs) were calculated using Cox regression analysis. Over a median follow-up of 55 months, 790 cases of UGI cancers were recorded. 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) increased UGI cancer risk (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 (HR_Q4vs.Q1 = 0.69, 95% CI: 0.49-0.98), whereas an unhealthy PDI increased the risk (HR_Q4vs.Q1 = 1.92, 95% CI: 1.38-2.67). The study concludes that unbalanced diets elevate UGI cancer risk, while balanced, plant-based diets reduce it. Promoting healthier dietary habits may benefit high-risk populations.