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| Cancer Epidemiol Biomarkers Prev 1998 Aug;7(8):667-71 |
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Fiber
intake and risk of colorectal cancer.
Negri E, Franceschi S, Parpinel M, La Vecchia C.
Istituto di Ricerche Farmacologiche Mario Negri, Milan, Italy.
The relationship between various types of fiber and colorectal
cancer risk was investigated using data from a case-control
study conducted between January 1992 and June 1996 in Italy.
The study included 1953 cases of incident, histologically confirmed
colorectal cancers (1225 colon cancers and 728 rectal cancers)
admitted to the major teaching and general hospitals in the
study areas and 4154 controls with no history of cancer admitted
to hospitals in the same catchment areas for acute nonneoplastic
diseases. Dietary habits were investigated using a validated
food frequency questionnaire. Odds ratios (ORs) were computed
after allowance for age, sex, and other potential confounding
factors, including physical activity and protein, fat, and carbohydrate
intake. Fiber was analyzed both as a continuous variable and
in quintiles. For most types of fiber, the OR of colon and rectal
cancers was significantly below 1, and no appreciable differences
emerged between the two. When the unit was set at the difference
between the upper cutpoints of the fourth and first quintile,
i.e., the 80th and 20th percentiles, the ORs for colorectal
cancer were 0.68 for total fiber (determined by the Englyst
method as nonstarch polysaccharides), 0.67 for soluble noncellulose
polysaccharides (NCPs), 0.71 for total insoluble fiber, 0.67
for cellulose, 0.82 for insoluble NCPs, and 0.88 for lignin.
When fiber was classified according to the source, the OR was
0.75 for vegetable fiber, 0.85 for fruit fiber, and 1.09 for
cereal fiber. The ORs were similar for the two sexes and the
strata of age, education, physical activity, family history
of colorectal cancer, and energy intake. Likewise, no appreciable
differences emerged when subsites of the colon and rectum were
investigated separately. This study provides additional support
for a protective and independent effect of fiber on colorectal
cancer, particularly for cellulose and soluble NCPs, and of
fiber of vegetable or fruit origin.
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