Context Some epidemiologic studies suggest that elevated fruit and vegetable
consumption is associated with a reduced risk of breast cancer. However, most
have been case-control studies in which recall and selection bias may influence
the results. Additionally, publication bias may have influenced the literature
on associations for specific fruit and vegetable subgroups.
Objective To examine the association between breast cancer and total and specific
fruit and vegetable group intakes using standardized exposure definitions.
Data Sources/Study Selection Eight prospective studies that had at least 200 incident breast cancer
cases, assessed usual dietary intake, and completed a validation study of
the diet assessment method or a closely related instrument were included in
these analyses.
Data Extraction Using the primary data from each of the studies, we calculated study-specific
relative risks (RRs) that were combined using a random-effects model.
Data Synthesis The studies included 7377 incident invasive breast cancer cases occurring
among 351 825 women whose diet was analyzed at baseline. For comparisons
of the highest vs lowest quartiles of intake, weak, nonsignificant associations
were observed for total fruits (pooled multivariate RR, 0.93; 95% confidence
interval [CI], 0.86-1.00; P for trend = .08), total
vegetables (RR, 0.96; 95% CI, 0.89-1.04; P for trend
= .54), and total fruits and vegetables (RR, 0.93; 95% CI, 0.86-1.00; P for trend = .12). No additional benefit was apparent
in comparisons of the highest and lowest deciles of intake. No associations
were observed for green leafy vegetables, 8 botanical groups, and 17 specific
fruits and vegetables.
Conclusion These results suggest that fruit and vegetable consumption during adulthood
is not significantly associated with reduced breast cancer risk.