D3 is made by irradiating lanolin (from sheep wool) with UV light [1]. Natural source of D3 is oily fish, beef liver. It's the Vitamin D2 that is made from fung

D3 is made by irradiating lanolin (from sheep wool) with UV light [1]. Natural source of D3 is oily fish, beef liver. It's the Vitamin D2 that is made from fungi - UV light helps to create it in mushrooms [2]. [1] https://www.quora.com/What-is-the-industrial-process-involved-in-making-Vitamin-D3?share=1 https://www.quora.com/What-is-the-industrial-process-involve... [2] https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/#h3 https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessiona...