Folic Acid Absorption Studies a Comparison of Two Microbiological Assay Techniques.

In the investigation of malabsorption syndromes and folic acid deficiency, the folic acid absorption test may be used to determine the degree of absorption of folic acid from the intestine and also to measure the rate of clearance from the serum . The test is based on loading the patient with subcutaneous folic acid followed by an oral dose of this vitamin. Samples of blood are withdrawn at suitable intervals after the administration of the oral dose. The folic acid activity of the serum obtained from these samples is assayed microbiologically using Streptococcus faecalis as the test organism by Pitney, Joske and Mackinnon (1). More recently, Lactobacillus easel has been used to determine physiological levels of serum folic acid activity by Herbert (2), Waters and Mollin (3), and Davis and Kelly (4). S. f zecalis is not a suitable organism for this assay as it does not appear able to utilize the more complex forms of folic acid normally present in serum. It seemed therefore that it may be possible to use L. casei as an alternative to S. faecalis as the test organism for folic acid absorption studies. It is the purpose of this paper to compare the results obtained in a series of twenty folic acid absorption studies using both L. easel and S. faecalis as the assay test organisms.