I also think a very large majority of people on this planet are tired because of an unknown deficit of vitamines and minerals like Omega 3, Zink and Vitamin D
I never ate much meat but I do eat fermented-only dairy. I got my bloodwork done and I am iron deficient. I am taking the bisglycinate salt which is completely unnoticeable on my stomach. I'll have it retested after a course of 5000mg elemental iron equivalents (about a month). My mood noticeably improved after checking and correcting my blood vitamin and iron levels.
Also high CO2 in working and sleeping areas. Basically any older building without HVAC and with upgraded (double pane) windows.
Most home HVAC systems don’t bring in fresh air, right? Just recirculate air in the house.
V in HVAC is for "ventilation" and although home AC unit might not provide it itself, I'd be surprised if there really wasn't any. Unlike AC, V is mandated by law in many jurisdictions.
The ones I know suck air out of the building (well, really, create a mild low pressure), and rely on fresh air getting in elsewhere (for example through dedicated intakes around windows in apartments.)
Newer homes are supposed to have heat recovery ventilators, which do bring in fresh air even if all windows are closed.
Is there any research to back that claim up?
Vitamin D deficiency is well known enough it should stand up to the simple concern trolling done by people who demand a source like every post must be an academic journal.