Vitamin B12, also known as cobalamin, is essential for numerous metabolic processes, including the manufacture of DNA and RNA. It also plays an important role in maintaining healthy nerve cells and red blood cells.
Attempts to link large intakes of B12 with an improvement in survival from prostate cancer or a reduced risk of developing prostate cancer have not proved successful. (Kasperzyk 2009) In fact, several studies indicate that elevated levels of B12 may actually increase the risk of prostate cancer. A Swedish study, for example discovered that elevated levels of B12 in the blood may triple the risk of developing prostate cancer. (Hultdin 2005) This was not the only one: results from the European Prospective Investigation into Cancer and Nutrition Study found that high levels of B12 may be associated with an increased risk of developing advanced prostate cancer. (Johansson 2008)
Vitamin B12 is found in fish, shellfish, meat, and dairy foods—fruits and vegetables don’t contain this nutrient. The RDA is 2.4 mcg daily for adults. Because up to 30 percent of people older than 50 do not absorb vitamin B12 efficiently from food, a vitamin B12 supplement may be needed. Aside from an inability to properly absorb the vitamin, a B12 deficiency is rare, mainly because the body can store several years’ worth of the vitamin. Exceptions to the possibility of a deficiency include the elderly, strict vegetarians, and those who have pernicious anemia, which is characterized by an inability to absorb vitamin B12 properly.
Hultdin J et al. Plasma folate, vitamin B12, and homocysteine and prostate cancer risk: a prospective study. Int J Cancer 2005; 113(5): 819-24.
Johansson M et al. Circulating concentrations of folate and vitamin B12 in relation to prostate cancer risk: results from the European prospective Investigation into Cancer and Nutrition study. Cancer Epidemiol Biomarkers Prev 2008; 17(2): 279-85.
Kasperzyk JL et al. One-carbon metabolism-related nutrients and prostate cancer risk. Am J Clin Nutr 2009 July 1.