Studies have revealed that high blood levels of selenium may be protective against advanced prostate cancer. Turkey has about 25 micrograms of selenium per half cup. Canned tuna has about 65 micrograms per 3-ounce serving. Just keep the sandwich lean by choosing low-fat or nonfat mayo.

In addition to turkey and tuna, other food sources of selenium include Brazil nuts, wheat flour, part-skim ricotta cheese, and pork. Selenium is a trace mineral, which means that your body only needs a small amount of it. The RealAge Optimum dose of selenium is 200 micrograms per day. Too much selenium can be toxic to your system, so opt for food sources rather than supplements. In a study, adequate selenium intake was linked to a reduced risk of advanced prostate cancer; however, it did not appear to affect prostate cancer risk on the whole. When adding selenium-rich fish to your diet, avoid fish varieties that tend to be highest in mercury, such as long-lived fish.