 The day after you are discharged from the GCRC, you will be asked to eat, for a period of approximately 4 weeks, a diet containing reduced amounts of vitamin B6 and limit the amount of caffeine in coffee, tea, and carbonated drinks you drink to one to two per day. Twice each day during this approximately 4 week period you will come to the General Clinical Research Center GCRC at Shands Hospital where you will eat your breakfast and evening meals. Also, you will be weighed once daily and have your heart rate, respirations and blood pressure monitored twice weekly. You will be given a sack lunch to be consumed wherever you choose. To be sure that you are getting adequate amounts of all nutrients except the vitamin being studied, you will be given a pill containing a vitamin and mineral supplement each day. Once each week when you come into the GCRC to eat breakfast, you will have two teaspoons of blood taken from a vein in your arm to allow monitoring of your vitamin B6 status. 