In most studies, higher levels of vitamin D in a population are associated with less prostate cancer. Studies also suggest that using vitamin D may improve outcomes from treatment. Food sources of vitamin D include oily fish (salmon, mackerel, tuna, herring, cod liver oil), and dark green leafy vegetables. Your body also produces vitamin D naturally when sunlight strikes your skin.
About 800 IU of vitamin D daily is a reasonable supplement for Portland-area people, who are more likely to be deficient in the vitamin than those from sunnier climes; less might be fine for people who spend more time in the sun.
A study involving high-potency vitamin D (calcitriol, which is by prescription only) combined with the chemotherapy agent docetaxel (Taxotere) for patients with hormone-refractory prostate cancer showed some benefit, but there is potential for serious side effects.
