Vitamin B12 - a scoping review for Nordic Nutrition Recommendations 2023

Abstract

Vitamin B₁₂ (cobalamin) is essential for normal metabolic function, and even moderate deficiency of this vitamin has negative health effects. Vitamin B₁₂ is found in animal foods, and as vegetarian diets are increasingly popular in Western countries, one might expect a higher prevalence of vitamin B₁₂ deficiency in the Nordic population. Setting recommendations for vitamin B₁₂ intake has proven to be difficult, as uptake of vitamin B₁₂ varies substantially, the clinical deficiency symptoms are often diffuse, and there is no clear agreement on the decision limits for vitamin B₁₂ deficiency. Vitamin B₁₂ deficiency is reported to be particularly common among pregnant women and infants, despite the fact that less than 1% of Norwegian pregnant women have a cobalamin intake below the Nordic Nutrition Recommendations 2012-recommended level of 2.0 µg/day. In addition, the assumption that breast milk contains sufficient vitamin B₁₂ for optimal health and neurodevelopment during the first 6 months of life does not comply with the high prevalence of insufficient vitamin B₁₂ status in this age group. Recommended intakes of vitamin B₁₂ vary among age groups and must be based on markers of cobalamin status, indicating an optimal intracellular biochemical status, and not merely absence of clinical signs of vitamin B₁₂ deficiency.

Keywords: Vitamin B12; cobalamin; homocysteine; methyl malonic acid; nutrition recommendations; one-carbon metabolism.