Table 3

Summary of dietary prevention of colorectal tumors in rats, mice and humans: efficacy of agents or diets to reduce tumor incidence in rats, polyp number in mice, and polyp recurrence in humans

Agent or dietaAOM-rats, colon tumor incidencebMin mice, polyp number, (small bowel)Humans, polyp recurrenceReferences and notes
%cNd%cNd%c
Selenium 50 7 60 3 50 95 e
Celecoxib 20 2 60 4 70 96 f
Aspirin90 70 4 80 97 g
Sulindac 60 8 50 1580 98 h
Calcium70 80 99 i
Wheat bran 60 9 80 490 100
Low fat 80 10± 70 1100 101 102 103 104 j
Caloric reduction 50 3 90 1 100 102 103 104 k
Fruits and vegetables1008120100 102 , 105 106 107
β-carotene 80 3110 104 , 108
Vit. C + vit. E10011110 108 109 110
Psyllium 40 1 160 111
  • a Agents or diets tested in clinical trials, ranked by efficacy in humans.

  • b Data come from a systematic review of positive rat studies (7) , pooled with null and negative published rat studies.

  • c Data are treatment effects, averaged from all published studies, and rounded to the nearest 10. Calculation: 100 × (colorectal tumor incidence in treated group)/(incidence in control group). A percentage <100 denotes a protective effect. Boldface, significant effect. Italics, value not firmly established (because from a single trial or a small size one or because the primary endpoint was not colon tumor). In mice column, polyp number was used in place of tumor incidence.

  • d Number of pooled studies. ±, some studies within the pool were clearly discrepant.

  • e Colon cancer was a secondary endpoint in the selenium trial, primarily designed to reduce prostate cancer.

  • f Polyp reduction shown in FAP patients. No data yet published on sporadic polyps.

  • g Significant effect of low dose of aspirin (80 mg/day), no effect of high dose (325 mg/day).

  • h Sulindac shows significant protection in FAP patients (three small-size trials), not on sporadic polyps (two trials) (4) .

  • i In Apc1638 mice (24) , the low-calcium “Western Diet” increased by +175% the tumor yield. This result was not included in the table because the diet was also low in vitamin D and high in fat.

  • j The effect of fat was significant in F344 rats (101) but not in SD rats (data not shown). In human volunteers, the interventions were in part, or led to, a dietary fat intake reduction (102 103 104) .

  • k The above-cited low-fat interventions also led to a reduction in caloric intake, estimated as −18%, −10%, and −5% in studies 102–104, respectively.