Vitamin B6 Dependence of One-Carbon Metabolism

Arm 1 glycine and leucine: A subset of 14 participants out of the total enrolled participants with an adequate nutritional status will undergo the tracer infusion of glycine and leucine amino acids protocol while an adequate vitamin pyridoxine, B6 status. After the first infusion each participant will then begin a diet low in vitamin B6 (\<0.5 mg/d) for 4 weeks to achieve marginal B6 status followed by a repeat of fasting blood sampling and tracer infusion protocol.

Arm 2 Intervention of Serine and methionine infusion: A subset of 14 participants out of the total enrolled participants. Received an adequate nutritional status will undergo the tracer infusion of methionine and serine amino acids protocol while in adequate vitamin pyridoxine, B6 status. After the first infusion each subject will then begin a diet low in vitamin B6 (\<0.5 mg/d) for 4 weeks to achieve marginal B6 status followed by repeat of fasting blood sampling and tracer infusion protocol.