> ... Vit D deficiency was probably endemic in the Winter months...but you don’t die from that...
Besides a lack of the sunshine vitamin, in the late winter months, people used to run out of vegetables and greens and ate mostly meats. They then contracted what was called “Cabin Fever” or “Spring Fever”. It was actually a lack of vitamins of various kinds. The contracted rickets, scurvey, beri-beri and many other things. When vegetables were available in the late spring, the diseases subsided.
The precise reason for the origin of the Christmas tree...tea made from evergreen needles kept our Euro ancestors alive during the winter. Good source of vitamin C...