Albumin Catabolic Rate Measured by a Stable Isotope

The goal of this physiological study is to compare albumin catabolic rate measured by a stable isotope labeled amino acid in healthy volunteers and in patients with liver disease. At steady state synthesis and catabolism or degradation are equal. The primary questions it aims to answer are: * Is albumin catabolic rate lower in patients with liver disease? * Is albumin catabolic rate measured by stable isotopes in volunteers like historical controls measured by radio-iodinated albumin at the investigator's laboratory or elsewhere? Subjects will be given an oral dose of the deuterium labeled amino acid phenylalanine that will be incorporated by the liver in newly synthetized albumin molecules, and blood samples will be taken over 12 weeks to determine the catabolic rate of albumin.