Why your Vitamin D supplements might not be working. Did you know that oral supplements have to go through your entire digestive system? This means you might not be absorbing what The Impact of Vitamin D and L Cysteine Co Supplementation on Upregulating Glutathione and Vitamin D Metabolizing Genes and in the Treatment of Circulating 25 Hydroxy Vitamin D Deficiency Vital Nutrients Glutathione 100 Capsules 400 mg Vitamin C, D, and Glutathione Injections: Supporting Immunity from the Inside Out Syn Wellness Center