Dietary fiber, vegetables, and colon cancer: critical review and meta-analyses of the epidemiologic evidence.
Whether colon cancer risk can be modified by a diet rich in vegetables, grains, and fruit, and, if so, whether the protective factor is dietary fiber or other biologically active components correlated with a high-fiber diet are questions of active research interest. Because studies on diet are susceptible to bias from a number of sources, in this review we evaluated the adequacy of study methodology as well as study results to clarify how much protection, if any, is conferred by a high-fiber diet. The review consisted of an aggregate assessment of the strength of evidence from 37 observational epidemiologic studies as well as meta-analyses of data from 16 of the 23 case-control studies. Both types of analyses revealed that the majority of studies gave support for a protective effect associated with fiber-rich diets; an estimated combined odds ratio (OR) of 0.57 (95% confidence interval = 0.50, 0.64) was obtained when the highest and lowest quantiles of intake were compared. Risk estimates based on vegetable consumption (OR = 0.48) were only slightly more convincing than those based on an estimate of fiber intake (OR = 0.58), but the data do not permit discrimination between effects due to fiber and nonfiber effects due to vegetables.
Trock
B
B
Fox Chase Cancer Center, Philadelphia, PA.
Lanza
E
E
Greenwald
P
P
D016022:Case-Control Studies; D003110:Colonic Neoplasms / Q000517:prevention & control*; D004043:Dietary Fiber / Q000008:administration & dosage*; D006801:Humans; D015201:Meta-Analysis as Topic; D012306:Risk; D014675:Vegetables