Dietary fiber, vegetables, and colon cancer: critical review and meta-analyses of the epidemiologic evidence

J Natl Cancer Inst. 1990 Apr 18;82(8):650-61. doi: 10.1093/jnci/82.8.650.


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.

Publication types

  • Meta-Analysis
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Case-Control Studies
  • Colonic Neoplasms / prevention & control*
  • Dietary Fiber / administration & dosage*
  • Humans
  • Meta-Analysis as Topic
  • Risk
  • Vegetables*