The Associations of Fruit and Vegetable Intakes with Burden of Diseases: A Systematic Review of Meta-Analyses

Background Low fruit and vegetable intakes are recognized risk factors for non-communicable diseases. This systematic review summarizes published meta-analyses of global burden of diseases attributable to low fruit and vegetable intakes, and the best relative risk estimates. Methods A published novel assessment process combining Cochrane Review measures, Assessing the Methodological Quality of Systematic Reviews checklist, and Newcastle-Ottawa Quality Assessment Scale was employed. Results Sixty-four reports investigating 98 riske-disease pairs were included in the systematic review. Fifty-six pairs from 39 reports were assessed as statistically significant, involving 29 burden of diseases. Dose responses were identified for 31 negative and two positive associations. High against low intake relative risks were identified for 22 negative and one positive association. The highest identified linear dose response for each 100 g/day increase in fruit intakes was 0.56 (95% CI 0.42 to 0.74) for esophageal cancer, followed by 0.72 (95% CI 0.59 to 0.87) for mouth, pharynx, and larynx cancer; nonlinear dose response for the first 100 g/day of fruit intakes were 0.86 (95% CI 0.84 to 0.88) for stroke, followed by 0.89 (95% CI 0.88 to 0.90) for all-cause mortality. The highest identified linear dose response for each 100 g/day increase in vegetable intakes was 0.88 (95% CI 0.80 to 0.95) for renal cell cancer, followed by 0.89 (95% CI 0.84 to 0.95) for non-Hodgkin lymphoma; nonlinear dose responses for the first 100 g/day of vegetable intake were 0.86 (95% CI 0.84 to 0.89) for coronary heart disease, followed by 0.87 (95% CI 0.84 to 0.90) for all-cause mortality. For nonlinear associations, clear increases in protective associations were observed with the first 200 g/day of intakes, whereas little further increase or even decrease in protective associations were reported beyond 300 g/day intakes. Canned fruit intakes were positively associated with all-cause and cardiovascular disease mortality, and pickled vegetable intakes were positively associated with stomach cancer. Conclusions This systematic review supports existing recommendations for fruit and vegetable intakes. Current comparative risk assessments might significantly underestimate the protective associations of fruit and vegetable intakes.