Is eating a mixed diet better for health and survival?: A systematic review and meta-analysis of longitudinal observational studies

The role of dietary diversity in chronic disease or survival is controversial. This meta-analysis quantified the health impact of dietary diversity. Random-effects models pooled risk ratios (RRs) and 95% confidence intervals (CIs) of 20 longitudinal studies. Total dietary diversity was associated with a 22% lower risk of all-cause mortality (RR 0.78 [95%CI: 0.64, 0.96]), and was inversely associated with incident cancer- or CVD-specific mortality only in subgroup analyses (RR range: 0.53 to 0.90, p < 0.05). Similarly, diversity across healthy foods was inversely associated with all-cause mortality (RR 0.84 [95%CI: 0.73, 0.96]). An inverse association between total diet diversity and incident CVD was significant in non-European populations consuming diets with diverse food groups (RR: 0.93 [95% CI: 0.86-0.99]). Effects on cancer risk are unstudied. Diversity within fruits and/or vegetables showed null associations for all outcomes, except potentially for squamous cell-type carcinomas. More robust research is warranted. Findings indicated greater dietary diversity may benefit overall survival.