American Journal of Clinical Nutrition, Vol 27, 700-705, Copyright © 1974 by The American Society for Clinical Nutrition, Inc.

Human serum retinol transport in malabsorption

¹ From the Department of Medicine, Columbia University College of Physicians and Surgeons, The Medical Service of The Presbyterian Hospital, and the Medical Service of the Harlem Hospital Center, New York, N. Y.

Using specific immunoassays for retinol-binding protein (RBP) and prealbumin (PA), the proteins responsible for serum vitamin A transport in man, the retinol transport system has been examined in 22 adults with malabsorption (mean stool fat 23 g/24 hr). Mean serum concentrations of vitamin A and RBP in these patients did not differ from normal, whereas PA levels were depressed (P < 0.001). This contrasted with the previously reported marked depression of all three components of the serum retinol transport system in patients with liver disease and the marked elevations of vitamin A and RBP in patients with renal failure. In patients with malabsorption, serum concentrations of vitamin A were correlated with RBP (r = 0.901, P < 0.001). These data are consistent with the hypothesis that patients effectively mobilize hepatic stores of vitamin A as a retinol-RBP complex during fat malabsorption. For this reason, serum vitamin A concentrations are a poor means of screening for malabsorption.