The results of numerous case-control studies indicate that eating a diet rich in fruits and vegetables decreases the risk of developing a number of different types of cancer, particularly cancers of the digestive tract (oropharynx, esophagus, stomach, colon, and rectum) and lung (19-21). The results of some of these studies were the foundation for the National Cancer Institute’s “5 a Day” program, which was aimed at increasing the fruit and vegetable consumption of the American public to a minimum of five servings daily. The current U.S. government campaign, Fruits & Veggies-More Matters™, has replaced the "5 a Day" program. In contrast to the results of case-control studies, many recent prospective cohort studies have found little or no association between total fruit and vegetable intake and the risk of various cancers (22-44). There are several possible explanations for this discrepancy. Case-control studies, in which the past diets of people diagnosed with a particular type of cancer are compared to the diets of people without cancer, are more susceptible to bias in the selection of participants and dietary recall than prospective cohort studies, which collect information on the diets of large cohorts of healthy people and follow the development of disease in the cohort over time (45). Although prospective cohort studies provide weak support for an association between total fruit and vegetable consumption and cancer risk, they provide some evidence that high intakes of certain classes of fruits or vegetables are associated with reduced risk of individual cancers. Higher intakes of fruits have been associated with modest but significant reductions in lung cancer risk in a pooled analysis of eight prospective cohort studies (28) and with reductions in risk of bladder cancer in some studies (46). In men, higher intakes of cruciferous vegetables have been associated with significant reductions in the risk of bladder cancer (47) as well as prostate cancer (48), and higher intakes of tomato products have been linked with significant reductions in risk of prostate cancer (49).
The results of numerous case-control studies indicate that eating a diet rich in fruits and vegetables decreases the risk of developing a number of different types of cancer, particularly cancers of the digestive tract (oropharynx, esophagus, stomach, colon, and rectum) and lung (19-21). The results of some of these studies were the foundation for the National Cancer Institute’s “5 a Day” program, which was aimed at increasing the fruit and vegetable consumption of the American public to a minimum of five servings daily. The current U.S. government campaign, Fruits & Veggies-More Matters™, has replaced the "5 a Day" program. In contrast to the results of case-control studies, many recent prospective cohort studies have found little or no association between total fruit and vegetable intake and the risk of various cancers (22-44). There are several possible explanations for this discrepancy. Case-control studies, in which the past diets of people diagnosed with a particular type of cancer are compared to the diets of people without cancer, are more susceptible to bias in the selection of participants and dietary recall than prospective cohort studies, which collect information on the diets of large cohorts of healthy people and follow the development of disease in the cohort over time (45). Although prospective cohort studies provide weak support for an association between total fruit and vegetable consumption and cancer risk, they provide some evidence that high intakes of certain classes of fruits or vegetables are associated with reduced risk of individual cancers. Higher intakes of fruits have been associated with modest but significant reductions in lung cancer risk in a pooled analysis of eight prospective cohort studies (28) and with reductions in risk of bladder cancer in some studies (46). In men, higher intakes of cruciferous vegetables have been associated with significant reductions in the risk of bladder cancer (47) as well as prostate cancer (48), and higher intakes of tomato products have been linked with significant reductions in risk of prostate cancer (49).
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