Glutathione deficiency is associated with impaired survival in HIV disease. Survival rates are 90% for those with glutathione levels above 0.91 and only 32% for those below 0.91. Supplementation with a whey-based oral supplement designed to provide glutathione precursors significantly increased glutathione levels and dramatically improved pulmonary function in a patient with obstructive lung disease. Cystine is the preferred form of cysteine for glutathione synthesis in macrophages and astrocytes and for immune enhancement.