 After finishing approximately 4 weeks on this diet, you will participate again in the procedure to test how effectively vitamin B6 functions in helping your body use certain amino acids. Again, this will involve giving you a solution of certain amino acids by a vein in your arm over the course of 9 hours. As before, you will report to the GCRC at approximately 8:00 p.m. on the evening before the procedure. You will spend the night at the GCRC and will not be allowed to eat after 9:00 p.m. The exact same procedures will be carried out as in the first admission. 