Abstract

BACKGROUND: Vegetables & fruit may protect against CVD risk and some types of cancer, but little evidence was found for an association with CVD death and total cancer risk or death. This raises questions about the association with death from all causes.
OBJECTIVES:

• To review all prospective studies which provided data about total fruits or vegetables, their subgroups, and specific types of vegetables and fruits, in relationship with all-cause mortality/survival.
• To define the amount of consumption found to be related with the described effects on death.
• To define possible effect modification by confounders.

DATA SOURCE: The Pubmed database was searched (No start date - July 6, 2009) for relevant articles using the keywords "prospective, cohort, follow-up, longitudinal" combined with "vegetables, fruit", and a fair amount of other keywords. The exact search term is described in the methods.
Prospective studies published in the English language were included. Reference lists were searched for additional articles.
RESULTS: 43 articles were found which provided information about 31 different cohorts.
Of these, 0 articles were excluded.
Results are described when any evidence for an association - as defined in the Methods - was found. In addition, data about total vegetables or fruits is described.

• Data about total vegetables was provided by 14 cohorts, including 10,093 cases. Significant protective effects were found in 3 cohorts, one of which was of moderate-large size, and two of which were of very small size. Suggestive evidence was found for a protective effect of vegetables against all-cause mortality. The level of consumption for this effect could not be defined, but no suggestion was found that very high consumption is needed.
• Data about total fruit was provided by 18 cohorts, including 19,444 cases. Significant protective effects were found in 5 cohorts, one of which was of moderate-large size, and four of which were of (very) small size. Suggestive evidence was found for a protective effect of fruit against all-cause mortality. No level of consumption could be defined for this effect.
• Data about soy was provided by 3 cohorts, including 73,844 cases. When all soy items were combined, significant protective associations were found in 3 cohorts of moderate to (very) large size. Soy consumption possibly protects against mortality. No level of consumption could be defined for this effect. Results were confined to publications about Japanese cohorts.
• Data about (green) leafy vegetables was provided by 3 cohorts, including a total of 18,275 cases. Significant protective associations were found in 2 cohorts of moderate-large size, and in part of a third cohort. Green leafy vegetables possibly protect against mortality.

CONCLUSION: Suggestive evidence was found for a protective effect of both total vegetables and total fruits against mortality. In addition, both soy and (green) leafy vegetables possibly protect against mortality. Results from the association with soy were confined to publications about Japanese cohorts. Since few significant effects were published in servings/cups/grams over a given time period, it is not possible to define specific amounts of consumption for these effects.
LIMITATIONS: No results were available from any of the cohorts of very large size (except for green-yellow vegetables and soy). It is to be expected that, in the coming decades, within these cohorts hundreds of thousands of subjects will decease. Since the current evidence is based on 10,093 and 19,444 deaths (for total vegetables and total fruits, respectively), it is not hard to understand that current evidence could change in any direction in the near future.
PERSPECTIVE: Evidence was judged about the relation with mortality only, but within the tables in this review results were added from publications about the relation with total major chronic disease. Three publications about 2 cohorts provided information about total major chronic disease in relation with various subgroups of vegetables & fruits, as well as with total vegetables & fruits (18). Inclusion of total major chronic disease in the model of mortality strenghtens the evidence for an association with green leafy vegetables, but does not change the evidence for any of the remaining variables,

Total vegetables and all-cause mortality/survival.

20 articles, providing information about 14 different cohorts were found, including a total of 10,093 cases.

Significant protective effects were found in 3 cohorts (7, 21, 24), and a protective association among men was found in another cohort (2), including a total amount of 6,084 cases (60 % of all cases).

Inclusion of intermediate levels of consumption:
Few articles provided data about specific amounts of consumption. Significant protective effects at any level of consumption are as follows:

• In the Spanish part of The EPIC Study (21) at an intermediate level of consumption: mean 183 g/day.
• Among participants with diabetes mellitus in The EPIC Study (21) at high consumption: ≥ 198 g/day.
• In the Italian part of The Seven Countries Study (24) at high consumption: ≥ 60 g/day.

Conclusion: Significant protective effects were found in 3 cohorts, one of which was of moderate-large size, and two of which were of very small size. Suggestive evidence was found for a protective effect of vegetables against all-cause mortality. The level of consumption for this effect could not be defined, but no suggestion was found that very high consumption is needed.

Total fruit and all-cause mortality/survival.

26 articles, providing information about 18 different cohorts were found, including a total of 19,444 cases.

Significant protective effects were found in 5 cohorts, including a total of 8,355 cases (8, 14, 21, 26, 32). In addition, nonsignificant protective associations were found in 2 cohorts (2 [men only], 16), including 1,132 cases. But nonsignificantly increased risks were also found in 2 cohorts (2 [women only], 15 [subjects aged ≥ 80 only]), including 506 cases.

Inclusion of intermediate levels of consumption:
Few articles provided data about specific amounts of consumption. Significant protective effects at any level of consumption are as follows:

• In the Spanish part of The EPIC Study (21) at high consumption ≥ 355 g/day.
• Among participants with diabetes mellitus in The EPIC Study (21) at an intermediate level of consumption: mean 195 g/day.

Conclusion: Significant protective effects were found in 5 cohorts, one of which was of moderate-large size, and four of which were of (very) small size. Suggestive evidence was found for a protective effect of fruit against all-cause mortality. No level of consumption could be defined for this effect.