Fruits and vegetables consumption and risk of non-Hodgkin's lymphoma: a meta-analysis of observational studies.

Epidemiologic evidence suggests that intakes of fruits and/or vegetables may play a role in the etiology of non-Hodgkin's lymphoma (NHL), but the findings are inconsistent. We aimed to assess fruits and/or vegetables intakes in relation to risk of NHL by a meta-analytic approach. We searched on PubMed database from January 1966 to September 2012 to indentify case-control and cohort studies. We used a random-effects model to compute summary risk estimates. For vegetables, the summary relative risks (RRs) of NHL for high versus low intake for case-control, cohort and all studies were 0.75 (95% CI, 0.60-0.94; N = 8), 0.90 (95% CI, 0.81-1.00; N = 5) and 0.81 (95%CI, 0.71-0.92; N = 13) ; and the corresponding RRs for intake of 1 serving per day were 0.88 (95% CI, 0.80-0.96; N = 8), 0.96 (95% CI, 0.92-1.00; N = 5) and 0.92 (95%CI, 0.87-0.96; N = 13). For fruits and vegetables combined, the summary RR for high versus low intake was 0.78 (95%CI, 0.66-0.92; N = 4), and for intake of 1 serving per day was 0.95 (95%CI, 0.91-1.00; N = 4). Regarding histological subtypes, vegetables intake was significantly inversely associated with diffuse large B-cell lymphoma and follicular lymphoma, but not small lymphocytic lymphoma/chronic lymphocytic leukemia (high vs. low intake, RR = 0.70, 0.70 and 1.01, respectively; N = 7, 7 and 10, respectively). Fruits intake was generally not associated with total NHL, or any histological subtypes. Our findings suggest that intakes of vegetables, and fruits and vegetables combined, but not fruits alone, significantly reduce risk of NHL.