Vitamin B12 (cobalamin) is synthesized only by microorganisms and humans must absorb it from foods. It is found in foods of animal origin, and especially abundant in foods of ruminant origin. The highest concentrations of vitamin B12 are present in offal (liver, kidney), but it is also present in fish, poultry and other meats. People who avoid animal products (vegetarians) should consider consuming meat alternatives, i.e. foods fortified with vitamin B12, or taking supplements. Vitamin B12 is required for formation of DNA as well as for healthy blood cells and proper functioning of nerve cells. Vitamin B12 deficiency is known as pernicious anemia and it is associated with neurological impairments. Also, low levels of vitamin B12 lead to hyperhomocysteinemia as risk factor of cardiovascular and metabolic diseases (diabetes).
DNA (genes) methylation
A very recent study investigated molecular changes (by comparing changes in DNA methylation) occurring after supplementation with vitamin B12 alone or combined with folic acid. The study was performed in children who were assigned into 4 groups (12 children per group), i.e. placebo, vitamin B12 supplemented, folic acid supplemented and B12 + folic acid supplemented groups. After 12 months of supplementation, significant changes in methylation of type 2 diabetes associated genes were observed in B12 supplemented and B12 + folic acid supplemented groups. These results led to conclusion that vitamin B12 might beneficially affect regulation of metabolically important genes (associated with diabetes).
- Yadav DK, Shrestha S, Lillycrop KA, et al. Vitamin B(12) supplementation influences methylation of genes associated with Type 2 diabetes and its intermediate traits. Epigenomics. 2018;10(1):71-90.
Brain is particularly vulnerable to vitamin B12 deficiency. Unfortunately, suboptimal B12 status is quite common and it occurs in 30 to 60 % of population. Deficit in vitamin B12 leads to hyperhomocysteinemia which is associated with cognitive impairments (i.e. cognitive decline, as seen in dementia and Alzheimer disease). One retrospective study investigated relationship between borderline vitamin B12 low status (≤ 350 pg/ml) and cognitive decline among 91 elderly patients with hip fracture. As a result, B12 levels ≤ 350 pg/ml were identified as independently associated with poorer cognition, evaluated by the Mini-Mental State Examination (MMSE) tool. Further on, recent meta-analysis investigate efficacy of vitamin B12 intake in decreasing levels of homocysteine associated with cognitive decline. In most of these studies, vitamin B12 was applied together with the folic acid and vitamin B6. As this meta-analysis concluded, vitamin B intake was associated with improvements in homocysteine blood levels.
Deficiency of vitamin B12 in early life is especially dangerous since it might affect the growth and development of brain with numerous neurodevelopmental consequences. One review study investigated evidences linking vitamin B12 status with cognition in children. It identified 17 studies on this subject and concluded that vitamin B12 insufficiency associates with the adverse cognitive outcomes (i.e. has a bad effect on attention, memory…). Still, there is a lack of randomized controlled trials investigating effects of B12 supplementation on cognition and brain development in children.
- Mizrahi EH, Lubart E, Leibovitz A. Low Borderline Levels of Serum Vitamin B12 May Predict Cognitive Decline in Elderly Hip Fracture Patients. Isr Med Assoc J. 2017;19(5):305-308.
- Zhang DM, Ye JX, Mu JS, Cui XP. Efficacy of Vitamin B Supplementation on Cognition in Elderly Patients With Cognitive-Related Diseases. J Geriatr Psychiatry Neurol. 2017;30(1):50-59.
- Venkatramanan S, Armata IE, Strupp BJ, Finkelstein JL. Vitamin B-12 and Cognition in Children. Adv Nutr. 2016;7(5):879-88.