| Agents | Effects |
| Aspirin | Very effective |
| NSAIDs (ibuprofen, sulindec etc.) | Probably effective |
| Vitamin E, Vit. C and beta carotene | Not effective |
| Folate | Effective if mostly obtained in diet |
| Calcium | Effective almost |
| Estrogen | Effective but have other problems |
| Fiber | Not effective |