Colon cancer risk: Data about (total) green vegetables was provided by 3 cohorts. A significantly increased risk among men was found in one cohort of small size (1), but a nonsignificant protective effect was found in another cohort of small size examining men (4). No association was found in the third cohort (25).
Data about green leafy vegetables was provided by a pooled analysis of 14 cohorts (29), and one additional cohort (24). No associations were found.

Rectal cancer risk: Data about the relation with rectal cancer risk was provided by 6 cohorts including a total of 977 cases (4, 6, 9, 24, 25). No (non)significant associations were found in any of the cohorts at any level of consumption.

Colorectal cancer risk: Data from articles about 4 cohorts was not stratified by cancer site (though information about colon cancer from 1 cohort was used by the pooled analysis: 23). A total of 5,106 cases were included in these cohorts.
Among men, a significant protective effect was found in the largest cohort (27), and a nonsignificant protective effect was found in another cohort (18). In the third cohort, no associations of high vs low consumption were found with light-green, or dark-green vegetables, but a protective effect of dark-green vegetables was noted with intermediate levels of consumption (30). These levels of consumption were not defined. Among women, no association of high vs low consumption was found in any of the cohorts (18, 23, 27, 30).

Mortality: Data about colorectal cancer mortality was provided by 2 cohorts. A protective effect against colon cancer mortality was found in the largest cohort among both men and women, but no information was provided about the strength, and significance of the association, and no adjustments for possible confounders were made (7). In the second cohort, a nonsignificant protective effect against rectal cancer mortality was found among men, but not women, and no associations were found with colon cancer mortality (22).

Conclusion: Few associations were found between green leafy vegetables and both colon, and rectal cancer risk. Among men, a significant protective effect against total colorectal cancer risk was found in one cohort of very large size, and a nonsignificant protective effect was found in another cohort of very large size. Inconclusive evidence was found for an association between green and/or leafy vegetables and colorectal, colon, or rectal cancer.

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