Vitamin B₁₂ and ageing: Current issues and interaction with folate

A compromised vitamin B₁₂ status is common in older people despite dietary intakes that typically far exceed current recommendations. The maintenance of an optimal status of vitamin B₁₂ is not only dependent on adequate dietary intake but more critically on effective absorption which diminishes with age. The measurement of vitamin B₁₂ is complicated by the lack of a gold standard assay. There are a number of direct and functional indicators of vitamin B₁₂ status; however, none of these are without limitations and should be used in combination. Vitamin B₁₂ is of public health importance, not only because deficiency leads to megaloblastic anaemia and irreversible nerve damage, but also because emerging evidence links low B₁₂ to an increased risk of a number of age-related diseases, including cardiovascular disease, cognitive dysfunction, dementia and osteoporosis. Furthermore, there are concerns relating to potential adverse effects for older adults with low vitamin B₁₂ status of over-exposure to folic acid in countries where there is mandatory fortification of food with folic acid. The aim of this review is to examine the known and emerging issues related to vitamin B₁₂ in ageing, its assessment and inter-relationship with folate.