Research shows that a deficiency of folate, part of the B complex of vitamins, is linked to cancer. Folate supplementation decreases colon cancer rates by 20 to 50 percent, but more than 50 percent of Americans don't even get the recommended amount, and 90 percent don't get the amount that seems to reduce colon cancer (800 micrograms a day).
Lots of foods like spinach, tomatoes, and orange juice contain folate, but it's absorbed less well than folic acid from supplements. The average intake of folate through food is 275 to 375 micrograms, so you need a supplement of about 400 micrograms to reduce your risk of cancer. That's especially important if you're allowing sun exposure to deplete your folate levels, which happens when you get more than 20 minutes of exposure to the sun a day. Be sure to add B6 and crystalline B12.