Vitamin D has been all over the news as the latest nutrient whose Recommended Daily Allowance has come under great scrutiny. Dietary vitamin D is unique in that it is not actually a vitamin and would be better classified as ‘pro-hormone D’.   We can thank Sir Edward Mellanby for the mishap in nomenclature going back to 1919 when the first notion of vitamin D being activated by sunlight was established.  In our closest attempt to imitate plant photosynthesis, when sunlight strikes...