The uptake of ingested vitamin B12 and its total body balance: a mathematical model suggests the optimal supplementation strategy

Impaired or insufficient uptake of vitamin B₁₂ causes neurological disorders, anemia, and various diffuse symptoms, all historically called pernicious anemia (PA). Maintenance of adequate B₁₂ body store (B) is important, but the recommended doses and duration of peroral B₁₂-supplementation are usually half-empirical. The current work suggests physiologically realistic algebraic equations to express the changes in B via the daily B₁₂-uptake. The data from literature were used to estimate the relevant parameters of the equations. The modeled values of B showed that the daily ingestion of B₁₂ = 3 × 2.0 μg maintains the steady state value of B = 1316/1858/2683 μg in healthy individuals with low/mean/high types of B₁₂-uptake. The "classical" PA-patients have a highly decreased intrinsic factor (falling from 30 μg of B₁₂-equivalents to below 0.2 μg), giving B = 47/81/123 μg for the low/mean/high B₁₂-uptakes and the aforementioned doses. Alignment of B with the combined index of B₁₂-status (cB12) in a heterogeneous cohort indicated that B > 1250 μg provides the safe B₁₂-status for >84 % of the subjects. The risk of PA is associated with B < 400 μg. Repletion of a low body store from B = 400 μg to ≈1250 μg would require a prolonged supplementation of healthy individuals with B₁₂-pills, if they receive 1 × 5 μg/day or 1 × 50 μg/day. These schemes are expected to raise B after the time intervals of (not possible)/2200/780 days or 2330/860/480 days, respectively. Only a pill with high B₁₂ = 5000 μg/day would raise B to 1250 μg in 24/16/10 days.