Case-control study on beneficial effect of regular consumption of apples on colorectal cancer risk in a population with relatively low intake of fruits and vegetables.

Laboratory in-vitro studies and animal experiments showing the potential health benefits from apples raises the question to what extent the regular consumption of apples in humans may have a beneficial effect on colorectal cancer risk. A total of 592 incident cases of colorectal cancer have been enrolled in a hospital-based case-control study. The comparison group included 765 controls chosen from the patients of the same hospital without history of cancer and admitted for treatment of nonneoplastic conditions. Interviews of both cases and controls were conducted in the hospital setting by trained interviewers. The median intake of fruits among cases was lower than in controls (9.5 vs. 11 servings/week) and the difference was statistically significant. Apples were the most frequent fruit consumed by the study participants and about 80% of variability in the total fruit consumption resulted from the intake of apples. We did not observe any significant statistical differences in consumption of berries, citrus, or stone fruits and other kinds of fruits across cases and controls. The adjusted estimates of colorectal cancer risk related to the daily consumption of apples (in quintiles) were based on the unconditional multivariate logistic model, which considered the set of potential confounding variables such as demographic characteristics of participants (age, gender, place of residency, marital status, tobacco smoking), total energy intake, intake of vegetables and fruits without apples. The results of the logistic analysis showed that the adjusted risk of colorectal cancer inversely correlated with daily number of apple servings. The reduced risk of colorectal cancer of border significance level was already observed at the consumption of at least one apple a day (odds ratio=0.65, 95% CI: 0.39-1.09), but at the intake of more than one apple a day the risk was reduced by about 50% (odds ratio=0.53, 95% CI: 0.35-0.79). Neither the consumption of vegetables nor other fruits have shown beneficial effects on the risk of colorectal cancer. The observed protective effect of apple consumption on colorectal risk may result from their rich content of flavonoid and other polyphenols, which can inhibit cancer onset and cell proliferation.