Evaluation of the Prevalence and Pathophysiology of Subclinical Vitamin A Deficiency in Malabsorptive States of Childhood

Abstract

The prevalence of subclinical vitamin A deficiency was investigated in children with chronic liver disease, cystic fibrosis, and gastrointestinal disease, all of whom received routine vitamin A supplements. Low serum vitamin A levels were found in patients with liver disease, and although a correlation was noted between the severity of liver disease and serum vitamin A levels, age of onset and duration of the liver disease may also influence vitamin A status. The major factors thought to cause vitamin A deficiency in such patients, malabsorption and retinol-binding protein (RBP) status, were investigated. Even though responses to an oral test dose of vitamin A were similar in a number of patients, the long term response to regular daily oral supplements was found to be varied, possibly as a result of differences in RBP status. Using successful liver transplant recipients as controls of similar age, serum total RBP levels were found to be reduced in patients with chronic liver disease, but not cystic fibrosis. However, serum total RBP levels in liver disease appeared to remain just within the normal range for age. Although apparently quantitatively normal, the serum RBP may have a reduced affinity for vitamin A, possibly resulting in reduced transport and therefore low serum vitamin A levels. Subclinical vitamin A deficiency was most prevalent in severe liver disease where oral vitamin A requirements appeared to be highly individual, therefore daily doses of vitamin A should probably be based on a dose per kg of body weight, and may be far in excess of 10,000iu of a watermiscible preparation. Dosage recommendations might be based on severity, duration and age of onset of liver disease, however the relative influences of these factors requires further investigation. Practically, regular measurement of serum vitamin A levels remains the most useful indicator of vitamin A status once the limitations have been recognised; especially when supported by measurement of serum total RBP levels.