Observational studies, primarily of a case-control design, have shown an inverse association of fruit and vegetable consumption with the risk of stomach cancer, a finding tentatively attributed to anti-oxidant vitamins. Ensuing randomized-intervention trials of these vitamins, however, have been mostly negative. Therefore, the seemingly protective effect of fruit and vegetables in case-control studies is suspected to be influenced by the information bias inherent in the retrospective assessment of exposure, particularly since pre-conceptions about the wholesome effects of these foods are common among the public. Our aim was to examine the association of fruit and vegetable intake with the risk of stomach cancer in a prospective cohort study. Fruit and vegetable consumption was assessed in 1967 in 11,546 individuals in the Swedish Twin Registry, along with a wide range of potentially confounding factors. Complete follow-up through 1992 was attained through record linkage to the National Cancer and Death Registers. The relative risk of stomach cancer was estimated in proportional hazards models, with confidence intervals (CIs) adjusted for correlated outcomes. The risk of stomach cancer was inversely related to fruit and vegetable consumption. Controlling for potentially confounding factors, the relative risk among subjects with the lowest compared to those with the highest intake was 5.5 (95% CI 1.7-18.3) with a statistically significant dose-risk trend (p
BACKGROUND: Several recent large prospective cohort studies have failed to demonstrate the presumed protective effect of fruit, vegetable, and dietary fiber consumption on colorectal cancer risk. To further explore this issue, we have examined these associations in a population that consumes relatively low amounts of fruit and vegetables and high amounts of cereals. METHODS: We examined data obtained from a food-frequency questionnaire used in a population-based prospective mammography screening study of women in central Sweden. Women with colorectal cancer diagnosed through December 31, 1998, were identified by linkage to regional cancer registries. Cox proportional hazards models were used to estimate relative risks. All statistical tests were two-sided. RESULTS: During an average 9.6 years of follow-up of 61 463 women, we observed 460 incident cases of colorectal cancer (291 colon cancers, 159 rectal cancers, and 10 cancers at both sites). In the entire study population, total fruit and vegetable consumption was inversely associated with colorectal cancer risk. Subanalyses showed that this association was due largely to fruit consumption. The association was stronger, however, and the dose-response effect was more evident among individuals who consumed the lowest amounts of fruit and vegetables. Individuals who consumed less than 1.5 servings of fruit and vegetables per day had a relative risk for developing colorectal cancer of 1.65 (95% confidence interval = 1.23 to 2.20; P(trend) =.001) compared with individuals who consumed more than 2.5 servings. We observed no association between colorectal cancer risk and the consumption of cereal fiber, even at amounts substantially greater than previously examined, or of non-cereal fiber. CONCLUSIONS: Individuals who consume very low amounts of fruit and vegetables have the greatest risk of colorectal cancer. Relatively high consumption of cereal fiber does not appear to lower the risk of colorectal cancer.
A number of prospective cohort studies have examined the relations of individual dietary variables to risk of colorectal cancer. Few studies have addressed the broader eating patterns that reflect many dietary exposures working together. Using data from a prospective study of 61,463 women, with an average follow-up period of 9.6 years (between 1987 and 1998) and 460 incident cases of colorectal cancer, the authors conducted a factor analysis to identify and examine major dietary patterns in relation to colorectal cancer risk. Using proportional hazards regression to estimate relative risks, the authors found no clear association between a "Western," "healthy," or "drinker" dietary pattern and colorectal cancer risk. However, the data suggested that consuming low amounts of foods that constitute a "healthy" dietary pattern may be associated with increased risks of colon and rectal cancers. An inverse association with the "healthy" dietary pattern was found among women under age 50 years, although the number of cancers in this age group was limited and interpretation of this finding should be cautious. In this age group, relative risks for women in increasing quintiles of the "healthy" dietary pattern, compared with the lowest quintile, were 0.74 (95% confidence interval (CI): 0.41, 1.31), 0.69 (95% CI: 0.39, 1.24), 0.59 (95% CI: 0.32, 1.07), and 0.45 (95% CI: 0.23, 0.88) (p for trend = 0.03). The role of overall eating patterns in predicting colorectal cancer risk requires further investigation.
The incidence of adenocarcinoma of the oesophagus has increased rapidly in recent decades. In order to appreciate the potential for prevention by means of dietary modification, we estimated the aetiological fractions and the increments in absolute risk attributable to low intake of fruit and vegetables for adenocarcinoma and squamous cell carcinoma of the oesophagus and for adenocarcinoma of the gastroesophageal junction. We conducted a nationwide population-based case-control study in Sweden, with participation of 608 cases and 815 controls. We used unconditional logistic regression to estimate relative risks, from which we calculated aetiological fractions. Individuals in the highest exposure quartile (median 4.8 servings/day) versus the lowest (median 1.5 servings/day) showed approximately 50% lower risk of oesophageal adenocarcinoma and 40% lower risk of oesophageal squamous cell carcinoma, but no risk reduction for gastric cardia adenocarcinoma. Approximately 20% of oesophageal adenocarcinoma, and likewise squamous cell carcinoma, in Sweden was attributed to consuming less than three servings of fruit and vegetables per day. A very large number of individuals (over 25,000) would need to increase their fruit and vegetable consumption moderately in order to prevent one oesophageal cancer per year. Moderate relative risk reductions translate into weak absolute risk reductions for oesophageal cancers in Sweden.