Citrus fruit intake and gastric cancer: the Stomach cancer Pooling (StoP) project consortium

Diets rich in vegetables and fruit have been associated with reduced risk of gastric cancer, and there is suggestive evidence that citrus fruits have a protective role. This study aimed at evaluating and quantifying the association between citrus fruit consumption and gastric cancer risk. We conducted a one-stage pooled analysis including 6340 cases and 14,490 controls from 15 case-control studies from the Stomach cancer Pooling (StoP) Project consortium. Odds ratio (OR) and the corresponding 95% confidence intervals (CI) of gastric cancer across study-specific tertiles of citrus fruit intake (grams/week) were estimated by generalized linear mixed effect models, with logistic link function and random intercept for each study. The models were adjusted for sex, age, and the main recognized risk factors for gastric cancer. Compared to the first third of the distribution, the adjusted pooled ORs (95% CI) for the highest third was 0.80 (0.73-0.87). The protective effect of citrus fruits increased progressively until three servings/week and levelled off thereafter. The magnitude of the association was similar between cancer sub-sites and histotype. The analysis by geographic area showed no association in studies from the Americas. Our data confirm an inverse association between citrus fruit intake and gastric cancer and provide precise estimates of the magnitude of the association. However, the null association found in studies from America and in some previous cohort studies prevent to draw definite conclusions on a protective effect of citrus fruit consumption.