The Effect of Intrinsic Factor on the Absorption of Vitamin B12 in Older People

Abstract

Determinations of the vitamin B₁₂ level in the plasma were made on 201 persons between the ages of 37 and 92 years. A statistically significant decline in the plasma vitamin B₁₂ level with age was found. This decline, calculated by the method of least squares, was 0.00521 mµg per ml of plasma per year of age. Schilling assays were done on twenty elderly subjects. Administration of intrinsic factor increased the urinary excretion of radioactive vitamin B₁₂ in those who had poor vitamin B₁₂ absorption as well as low plasma levels. On the other hand, the subjects with a urinary excretion of vitamin B₁₂Co⁶⁰ in the normal range, but with low plasma levels, did not show a statistically significant change when intrinsic factor was given in addition to vitamin B₁₂. Thirty-eight people with low normal plasma vitamin B₁₂ levels (0.3 to 0.5 mµg per ml) were given vitamin B₁₂ orally for five months. There was a statistically significant increase in plasma concentration of vitamin B₁₂. However, the increase in the amount of vitamin B₁₂ in the plasma was just as great when intrinsic factor was given with vitamin B₁₂ as when the subjects received vitamin B₁₂ alone. No evidence for any inhibitory activity of the intrinsic preparations was found.