B12 and Chronic Disease: Cancer

Summary: There is some evidence that a low B12 intake could play a role in the development of cancer.

To be confident of a link between a nutrient deficiency and cancer, numerous prospective studies should be conducted showing such an association. As of May of 2002, there was only one prospective study performed with the purpose of examining the relation between B12 and cancer (discussed below), and it was not performed on people with especially low B12 levels. Thus, there is not a lot of evidence one way or the other at this time. On the other hand, there is some evidence that low B12 intakes increase DNA damage which could then lead to cancer.

B12 and DNA Damage

It is thought that since B12 is needed for proper DNA production, a lack of B12 could have an effect on cancer through the incorporation of uracil into DNA. This can cause chromosome breakage resulting in a cancerous cell.¹ The same can be said of folate.¹

Fenech² studied folate and B12 levels and intake in respect to DNA damage in white blood cells (lymphocytes) which has been shown to be a good marker for future cancer. They found that serum B12 > 405 pg/ml and a supplemental intake of 7 µg of B12/day was optimal for reducing DNA damage. The subjects were not vegetarian.

Notes for B12 and DNA Damage

1. Ames BN. DNA damage from micronutrient deficiencies is likely to be a major cause of cancer. Mutat Res. 2001 Apr 18;475(1-2):7-20.

2. Fenech M. Micronucleus frequency in human lymphocytes is related to plasma vitamin B12 and homocysteine. Mutat Res. 1999 Jul 16;428(1-2):299-304.

B12 and Breast Cancer

In the only prospective study looking at B12, folate, B6 and breast cancer, Wu et al.¹ (1999, USA) found no association between serum folate or B6. There was a small increased risk for the postmenopausal women in the lower one-fifth of B12 levels (averaging 280 pg/ml) in one of the two groups studied. In the other group, where lower levels of B12 were not associated with increased risk, the women in the lowest one-fifth of serum B12 levels averaged 312 pg/ml, which are higher than average B12 levels in vegans who do not supplement (which tend to be around 200 pg/ml).

Notes for B12 and Breast Cancer

1. Wu K, Helzlsouer KJ, Comstock GW, Hoffman SC, Nadeau MR, Selhub J. A prospective study on folate, B12, and pyridoxal 5'-phosphate (B6) and breast cancer. Cancer Epidemiol Biomarkers Prev. 1999 Mar;8(3):209-17.