Part 3/14:
However, in the 1920s, the isolation of vitamin D as a supplement changed the landscape. Extracted from sources like cod liver oil, it became widely available for purchase in pill form, initially marketed toward children, pregnant women, and even "delicate men." With technological advances, chemists learned to synthesize vitamin D in labs, a process involving sheep wool grease containing cholesterol derivatives and UVB exposure in controlled environments. This revolutionized the approach to deficiency, shifting reliance from natural sunlight and diet to supplements.