From mefi: You may need more Vitamin D than you think
New research suggests that taking vitamin D, preferably D3, may prevent up to half of the cases of breast cancer and two-thirds of the cases of colorectal cancer in the United States. Vitamin D3 is produced by your body when your skin is exposed to sunlight. (You can also get it from fatty fish, egg yolks, fortified milk and other products, and supplements. D3 supplements are usually produced from lanolin, so vegans will prefer D2.)
