Fruit and vegetable consumption and risk of esophageal cancer in the Asian region: a systematic review and meta-analysis

The consumption of fruit and vegetables was reported to be associated with a reduced risk of esophageal cancer (EC) in many studies of esophageal adenocarcinoma (EAC) and esophageal squamous cell carcinoma (ESCC) from different regions worldwide. Therefore, to provide precise information to reduce the risk of EC in Asia, we performed a systematic review and meta-analysis of studies conducted in the Asian region about fruit and vegetable consumption and the risk of EC. We searched the MEDLINE (PubMed) and ICHUSHI (Japana Centra Revuo Medicina) databases from January 2010 to December 2020. The summary relative risk (SRR) and 95% CI were calculated using a random-effects model. In addition, I² statistics were used to detect heterogeneity. Twenty-two studies were eligible for meta-analysis (16 case–control studies and 6 cohort studies). The SRR for the lowest versus highest fruit consumption was 0.64 (95% CI 0.53–0.77, I² = 82%). That for the lowest versus highest vegetable consumption was 0.61 (95% CI 0.50–0.74, I² = 81%). Based on subgroup analysis, a validated Food Frequency Questionnaire (FFQ) was significantly associated (SRR for fruit: 0.54; 95% CI 0.40–0.74, SRR for vegetable: 0.60; 95% CI 0.48–0.76) with low heterogeneity (I² = 48% for fruit, I² = 0% for vegetables). Egger’s funnel plot asymmetry test demonstrated publication bias (P < 0.001 for fruit, P = 0.009 for vegetables). Fruit and vegetable consumption might be associated with a lower risk of EC in the Asian region. However, further substantial prospective studies with a validated FFQ and well-controlled important confounding factors are required to confirm the association.