GI Cancers are some of the nastist, deadliest and most common forms of cancer. Oral (mouth) cancer is disfiguring and is just as deadly as it was decades ago. Colon cancer is the same: it can really only be detected by a colonoscopy, an unpleasant procedure often skpped by the middle aged and senior crowd who need it most. Stomach cancer is little better. It is the second most deadly form of cancer and often goes undetected until it is too late.
Most Peak Testosterone do not like surprises, especially ones that shorten their lifespans or destroy their quality of life. And that is exactly what GI cancers are notorious for doing. Imagine spending years guarding and building your health only to find that a silent invader has stolen all your hard work Below we show you to avoid these silent killers:
1. Alcohol. Alcohol improves cardiovascular mortality rates. Unfortunately, it has a dark side: it increases the risk for all GI cancers. See this link on Alcohol for details.
2. Green Tea. Some studies show that green tea lowers GI cancers by almost two thirds. For more details, see this link on Cancer Protection.
3. Vitamin D and Calcium. One study (of women) found a substantial reduction in all cancers based on these two heavy hitters.  The reason that these may be so important in preventing colon cancers specifically is that they are tied into apotosis rates, i.e. how fast cells kill themselves. In other words, as Vitamin D and Calcium levels decrease, cell death decreases leading to increased cancer risk. 
4. Broccoli Sprouts and H. Pylori. One of the key risk factors for stomach cancer is H. Pylori, a generally silent bacteria that sits in the stomach in some people undetected and unnoticeable. Well, sometimes it leads to ulcers and other problems, but in many people it stays resolutely hidden. Interestingly enough, broccoli sprouts seems to thwart the little critters. Sulfurophane, one of the super chemicals prevalent in broccoli, is probably responsible as it can be a potent antibiotic. 
1) Amer J of Clin Nutr, Jun 2007, 85(6):1586-1591, "Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial"
2) Cancer Epidemiology, Biomarkers & Prev, Feb 2005, 14:525, "Calcium, Vitamin D, and Apoptosis in the Rectal Epithelium"