Which should we eat, fruit or vegetables? The association with abdominal aortic aneurysm

Long-term consumption of a Mediterranean diet (including high consumption of fruit and vegetables) increases circulating levels of endothelial progenitor cells more than a low-fat diet in patients with type-2 diabetes. Furthermore, adherence to the Mediterranean diet and adoption of an active lifestyle are inversely associated with incidence of cardiovascular disease. Consumption of fruit and/or vegetables has been known to be inversely associated with risk of hypertension, type 2 diabetes mellitus, and metabolic syndrome. Fruit/vegetable consumption may be also inversely associated with risk of cardiovascular disease (not only incidence but also mortality), especially coronary heart disease and stroke. The association of fruit/vegetable consumption with risk of abdominal aortic aneurysm (AAA), however, has been less investigated. In the present article, to assess whether consumption of either fruit or vegetables, both fruit and vegetables, or neither fruit nor vegetables is associated with incidence of AAA, we performed the first meta-analysis of currently available all prospective cohort studies. To identify all prospective cohort studies researching the association of fruit/vegetable consumption with AAA incidence, we searched PubMed, Web of Science and Google Scholar up to July 2019. Search terms included fruit(s) or vegetable(s); aorta or aortic; and aneurysm(s). From each study, we extracted multivariable-adjusted hazard ratios (with their 95% confidence intervals (CIs)) of AAA incidence for higher versus the lowest fruit or vegetable consumption, then combined the specific estimates by means of inverse variance-weighted averages of logarithmic hazard ratios in the random-effects model. All analyses were conducted using Review Manager version 5.3. We identified three large population-based prospective cohort studies (Table 1) enrolling 120,055 participants. Incidence rates of AAA during follow-up of 13 to 23 years was 0.52% to 3.83%. All studies provided multivariable-adjusted hazard ratios for fruit and vegetables separately. We excluded a study reporting hazard ratios for fruit and vegetables together. In all studies, smoking and socioeconomic status (education and physical activity) were entered into the multivariable Cox proportional hazards regression as potential covariates in addition to fruit/vegetables consumption (Table 1), which means that the inverse association of fruit, not vegetable, consumption with AAA incidence (demonstrated in the present metaanalysis) is ‘independent’ of smoking and socioeconomic status. A sex-stratified analysis was performed in only one study, which suggests that men (hazard ratio for the fourth versus lowest quartile consumption, 0.79: 95% CI, 0.64 to 0.99), not women (corresponding hazard ratio, 0.71; 95% CI, 0.45 to 1.11), benefit from fruit consumption. Unfortunately, no study reported patient ethnicity. Fruit and vegetable consumption was assessed by a 168-item food frequency questionnaire (FFQ) and a 1-h interview, a 66-item FFQ, and a 96-item FFQ. In a study by Bergwall et al., fruits were divided into citrus and non-citrus fruits; vegetables were, in addition to total vegetables, divided into root vegetables (including carrots), leaf vegetables (including kale), carrots, and cabbage; and juices (including all types of vegetable and citrus juices) were excluded. In other studies, however, fruit/ vegetable consumption was not especially defined. Bergwall et al. provided hazard ratios for citrus fruit, non-citrus fruit, leaf vegetables, and root vegetables separately, and Stackelberg et al. reported