To assess, through meta-analysis, the magnitude of the relation between fruit and vegetable consumption and the risk of coronary heart disease (CHD).

• Only prospective cohort studies were used for the meta-analysis
• Cohort studies were selected if they reported relative risks and 95% confidence intervals for coronary heart disease or mortality and if they presented a quantitative assessment of fruit and vegetable intake

• Articles in languages other than English
• Studies that reported cardiovascular events only
• Studies that reported combined cerebro- and cardiovascular events
• Individual fruits or vegetables

Recruitment

• Searches were conducted in electronic databases (MedLine and EMBASE) from 1970 to January 2006
• References from the extracted papers, reviews, and previous meta-analysis were also consulted to complete the data bank
• The electronic search included both free-text and MESH terms and was performed with the support of the laboratory librarian
• Search terms were described
• No attempt was made to contact authors of unpublished works or find articles in languages other than English.

Design:  Meta-Analysis 

Blinding used (if applicable):  not applicable 

Intervention (if applicable):  not applicable 

Statistical Analysis

• Pooled relative risks were calculated for each additional portion of fruit and/or vegetables consumed per day assuming a log-linear model
• Linearity of the associations were examined
• Heterogeneity among studies was assessed by Cochran's Q test
• Possibility of publication bias was assessed by funnel plot analysis and the Egger test

Timing of Measurements

Not applicable.

Dependent Variables

• Risk of coronary heart disease (CHD):  fatal and non-fatal myocardial infarction, ischemic heart disease mortality or coronary death, and coronary heart disease incidence

Independent Variables

• Fruit and vegetable consumption:  individual fruits and vegetables were not included
• Method involved a computation of the fruit and vegetable intake and not just the frequency of intake
• Food intake was assessed by means of food records, diet history records, and food frequency questionnaires

Control Variables

Initial N:  20 studies were identified.

Attrition (final N):  9 studies eligible for inclusion, consisting of 221,080 subjects (91,379 men, 129,701 women) and 5,007 CHD events.

• 4 studies were excluded for CHD events were pooled with cardiovascular or cerebrovascular events
• 4 studies were excluded because the food frequency questionnaire did not assess the quantity of fruit and/or vegetable intake
• 3 studies were excluded because there were insufficient data to extrapolate the relative risks

Age:  see Results

Ethnicity:  not specified

Other relevant demographics:

Anthropometrics

Location:  Finland and USA

Key Findings:

• The risk of CHD was decreased by 4% (RR = 0.96, 95% confidence interval: 0.93 - 0.99, P = 0.0027) for each additional portion per day of fruit and vegetable intake and by 7% (RR = 0.93, 95% confidence interval:  0.89 - 0.96, P < 0.0001) for fruit intake.
• The association between vegetable intake and CHD risk was heterogeneous (P = 0.0043), more marked for cardiovascular mortality (RR = 0.74, 95% confidence interval:  0.75 - 0.84, P < 0.0001) than for fatal and nonfatal myocardial infarction (RR = 0.95, 95% confidence interval:  0.92 - 0.99, P = 0.0058).

Other Findings

• Visual inspection of the funnel plot suggested a publication bias, although not statistically significant
• Therefore, the reported RRs are probably overestimated

In conclusion, this analysis presents evidence of a beneficial association between fruit and vegetable consumption and CHD risk, supporting the recommendation to eat a sufficient amount of fruit and vegetables to lower CHD risk.  The strength of this association, however, is still uncertain because of a possible publication or selection bias.  Furthermore, because observational studies do not control for unmeasured confounders, the causal mechanisms remain to be established in randomized controlled trials.  Finally, this study also points out the limited availability of cohort studies to analyze the relation between fruit and/or vegetable intake and CHD risk in Europe and Asia.

Analysis of the relation between vegetable intake and CHD risk revealed heterogeneity among studies.