The primary hypothesis in this study is that adding simple milk sugar (galactose) to the diet of Congenital Disorders of Glycosylation patients will normalize the metabolic abnormalities. The secondary hypothesis posits that galactose intervention in Congenital Disorders of Glycosylation patients will normalize specific physiological biomarkers of protein glycosylation that can be utilized for future phase II/III trial development. The knowledge gained from the investigation of these two aims will help the investigators learn more about the disrupted metabolic mechanism of this disease and should lead to the identification of new disease biomarkers that can be used to evaluate clinical efficacy in future therapeutic trials.