Eussen SJ, de Groot LC, Joosten LW, et al. Effect of oral vitamin B-12 with or without folic acid on cognitive function in older people with mild vitamin B-12 deficiency: a randomized, placebo-controlled trial. Am J Clin Nutr 2006;84(2):361-70.
In this-study, 195 participants with mild B-12 deficiency aged >=70 years were assigned to receive 1000mcg vitamin B-12, 1000mcg B-12 plus 400mcg folic acid, or placebo for 24 weeks. Cognitive function was assessed before and after treatment using a neuropsychological test battery including domains of attention, construction, sensomotor speed and memory. Memory function improved in the placebo group more so than in the group who only received B-12 (P = 0.0036). Neither B-12 supplementation alone, or in combination with folic acid, showed any improvement in cognitive function in test subjects after 24 weeks.
Zhang SM, Willett WC, Selhub J, et al. Plasma folate, vitamin B-6, vitamin B-12, homocysteine, and risk of breast cancer. J Natl Cancer Inst 2003;95(5):373-80.
In this prospective nested case-control study within the Nurse's Health Study, 32,826 women had blood samples obtained in 1989 and 1990 and were followed through 1996 for the development of breast cancer. 712 breast cancer patients and 712 matched controls were identified. Higher levels of plasma folate were associated with lower breast cancer risk especially in women with moderate alcohol consumption. (>= 15g/day) and in post menopausal women. Pre-menopausal women with the highest plasma B-12 levels also have lower breast cancer risk. The authors conclude that their findings suggest a chemopreventive role in breast cancer for folate and B-6 may contribute to a reduction in risk of breast cancer.