We Can Thank Poor Evolutionary Design for Vitamin D Deficiencies

My doctor recently declared me deficient in vitamin D and prescribed a weekly pill. Because I take care to eat a healthy and diverse diet, I was a bit annoyed. She said it was no big deal and actually very common, the medical equivalent of a parent telling a child, "Because I said so." Later on, I was grousing to some of my friends and many of them said they had gotten the same news. It made me wonder: What is going on with vitamin D? A Vexing Vitamin Truth be told, we shouldn't really ne