Vegetables, Fruit, and Colon Cancer in the lowa Women's Health Study

Abstract

Previous epidemiologic studies have shown an inverse association between vegetable and fruit consumption and colon cancer risk; few of these studies have been prospective or have focused on women. This report describes results from a prospective cohort study of 41,837 women aged 55-69 years who completed a 127-item food frequency questionnaire in 1986 and were monitored for cancer incidence for 5 years via the State Health Registry of Iowa. After specific exclusion criteria were applied, 212 colon cancer cases and 167,447 person-years were available for analysis. Intakes of 15 vegetable and fruit groups and dietary fiber were the major factors of interest. Consumption of garlic was inversely associated with risk, with an age- and energy-adjusted relative risk of 0.68 (95% confidence interval (CI) 0.46-1.02) for the uppermost versus the lowermost consumption levels. Inverse associations were also observed for intakes of all vegetables and dietary fiber; age- and energy-adjusted relative risks for the uppermost versus the lowermost intake quartiles were 0.73 (95% CI 0.47-1.13) and 0.80 (95% CI 0.49-1.31), respectively. Associations for the other vegetable and fruit groups were less remarkable.

Nutritional factors and colon carcinoma

“…A meta-analysis of 37 observational epidemiologic studbasis for a qualitative interaction. 14 In another meta-analysis of 19 case-control studies, 37 it was found females) as fructose, as did the consumption of simple sugar (OR Å 0.70 for males and 1.32 for females). To that grain fiber or cereal intake was either unrelated or positively associated with colon carcinoma risk.…”

Diet and cancer prevention

“…A 1992 meta-analysis of casecontrol studies supported this hypothesis (Howe et al, 1992), but a later re-analysis of these data, considering study heterogeneity and limited to studies with validated diet assessment instruments, did not support a role for fiber (Friedenreich et al, 1994). Most prospective cohort studies of dietary fiber and colon cancer risk have not supported an association (Heilbrun et al, 1985;Willett et al, 1990;Giovannucci et al, 1994;Steinmetz et al, 1994;Kato et al, 1997;Fuchs et al, 1999;Pietinen et al, 1999;Terry et al, 2001a;. However, a recent large European study involving 10 countries found a 25% lower risk of colon cancer associated with higher fiber intakes compared to low intakes (Bingham et al, 2003a).…”

Chemoprevention of Colorectal Cancer

“…Meta-analyses of case-control studies suggested, on average, a 50% reduction in the risk of development of CRC between the 2 groups. However, the published large prospective cohort studies showed equivocal findings [68,69,70], with the largest published study analyzing data on a study population of 19,541 with 16 years of follow-up showing no protective effect of dietary fibre against the development of CRC (RR = 1.08, 95% CI = 0.9–1.29) [71]. Similar findings were also obtained rom another trial using 958 subjects with 36 months of follow-up (RR = 1.00, 95% CI = 0.9–1.12).…”