To review evidence on the associations between vitamin B12 intake and its biomarkers, vitamin B12 intake and its functional health outcomes, and vitamin B12 biomarkers and functional health outcomes.

A systematic review was conducted by searching electronic databases, until January 2012, using a standardized strategy developed in the EURRECA network. Relevant articles were screened and sorted based on title and abstract, then based on full text, and finally included if they met inclusion criteria. A total of sixteen articles were included in the review.

Articles covered four continents: America (n 4), Europe (n 8), Africa (n 1) and Asia (n 3).

Population groups included healthy infants, children and adolescents, and pregnant and lactating women.

From the total number of 5815 papers retrieved from the initial search, only sixteen were eligible according to the inclusion criteria: five for infants, five for children and adolescents, and six for pregnant and lactating women.

Only one main conclusion could be extracted from this scarce number of references: a positive association between vitamin B12 intake and serum vitamin B12 in the infant group. Other associations were not reported in the eligible papers or the results were not provided in a consistent manner. The low number of papers that could be included in our systematic review is probably due to the attention that is currently given to research on vitamin B12 in elderly people. Our observations in the current systematic review justify the idea of performing well-designed studies on vitamin B12 in young populations.