Oral Vitamin B12 May Correct Deficiencies

WAGENINGEN, Netherlands--New research uncovered what scientists believe is the lowest oral dose of cyanocobalamin (vitamin B12) necessary to correct plasma markers of deficiency.

In the randomized, parallel-group, double blind study, published in this month's Archives of Internal Medicine (165, 10:1167-1172, 2005), scientists administered oral doses of 2.5, 100, 250, 500, and 1000 mcg/d of cyanocobalamin for 16 weeks in 120 older people with insufficient serum levels of vitamin B12 to find the lowest dose of oral cyanocobalamin necessary to produce 80 percent to 90 percent of the estimated maximal reduction in plasma methylmalonic acid concentration. Deficiency of the vitamin was defined as a serum vitamin B12 level of 100 to 300 pmol/L and a methylmalonic acid level of 0.26 µmol/L or greater. Orally delivered vitamin B12 in doses of 2.5, 100, 250, 500, and 1000 mcg/d was associated with respective mean reductions in plasma methylmalonic acid concentrations of 16 percent, 16 percent, 23 percent, 33 percent and 33 percent. Doses of 647 mcg/d to 1032 mcg/d of cyanocobalamin were associated with the greatest reduction in plasma methylmalonic acid concentration.

The researchers concluded the minimum dose of oral cyanocobalamin required to reverse mild vitamin B12 deficiency is more than 200 times greater than the recommended dietary allowance of approximately 3 mcg/d.