| Evidence |
Convincing |
Probable |
Possible |
| Substantially increased risk |
Cigarette smoking |
- |
- |
| Moderately increased risk |
- |
- |
- |
| Slightly increase risk |
Alcohol consumption for men |
- |
Pipe
Cigar
Environmental smoking |
| No association |
- |
Coffee, Tea, Vegetable
Vitamin A (carotenoids)
Vitamin C |
Total fluid Folate |
| Slightly decreased riske |
- |
Fruit |
- |
| Moderately Decreased risk |
- |
Selenium |
Vitamin E |
| Substantially decreased risk |
- |
- |
- |