Clinincal Briefs-By Louis Kuritzky, MD
Diet and Colorectal Adenomas
The epidemiologic basis implicating diet as a factor in the pathogenesis of colorectal cancer (CRC) is impressive. Not only do international studies and migration studies support such a role, animal studies show that manipulation of fat and fiber in the diet can alter the incidence of colonic tumors. Generally, ingestion of red meat and high dietary fat is associated with increased risk of CRC; vegetables, dietary fiber, and some micronutrients are associated with lower risk. The current study evaluated persons who had suffered an adenomatous polyp, a CRC precursor, to see if dietary alteration could reduce adenoma recurrence.
The Polyp Prevention Trial enrolled 2079 persons who had undergone colonoscopy and had resection of an adenoma, without evidence of CRC. Half of the group was assigned to a low-fat diet, high in fiber, fruits, and vegetables; the other half maintained their usual diet.
Dietary intervention reduced fat intake by almost 33%, but even persons in the usual diet group reduced their fat intake by about 6%. Overall, the mean absolute difference between the two groups was about 10%. Similarly, fruit and vegetable intake increased by about two-thirds in the intervention group, but changed only slightly in the usual diet group. All subjects underwent repeat colonoscopy four years later at the conclusion of the trial.
No difference in frequency of adenomatous polyp recurrence was detectable between the two groups. Similarly, there was no difference in the number of large or advanced adenomas. CRC diagnosis subsequent to randomization was actually substantially greater in the intervention group than in the control (by more than two-fold risk).
The authors conclude that dietary changes administered over four years do not demonstrate reduced likelihood of adenomatous polyp recurrence. COLOR=black>
Schatzkin A, et al. N Engl J Med 2000;342:1149-1155.
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