Moderation is considered as two drinks or less a day for men and one drink or less a day for women. Alcohol directly alters metabolism and causes excess weight gain, which decreases the strength of the immune system. Perhaps one of the best ways to prevent cancer is to avoid smoking and chewing tobacco. Smokeless tobacco is also related to causing cancer. It's linked to causing mouth cancer and increases risks of other cancers.
Quitting smoking can greatly reduce the risk of developing cancer.
Caffeine should also be limited in order to prevent cancer. Caffeine can have a negative impact on one's health. One side of effect of caffeine is disruption of sleep. Without sleep, the body's immune system does not work as well. It's harder for the body to fight infections and the body's energy level can be greatly decreased.