Wondering how people used to get vitamin D in the winter

Note: It appears that no vitamin D from the sun when 40 degrees away from equator in the winter.

• Burn the fat & vitamin D in the body which had been added with summer feasting

  • Winters were times of famine/fasting - and burning of fat and retrieving vitamin D stored in the fat

• Campfires? - some small amount of vitamin D

• Dried fish?

• Lard and many game meats had lots of vitamin D - which could be consumed in the winter

Since flame detectors sometimes monitor UV there must be some UV in a fire - perhaps enough to generate some vitamin D

• UV Flame Detector - Honeywell

• How to Select a Flame Detector

• WikiPedia Flame Detector

• WikiPedia Flame Detection

Flame Spectrum from WikiPedia: UV = purple area in lower left

Wonder about animals in the Northern Winters

• Do birds migrate South in the winter to get food AND vitamin D?

• Do mammals which do not migrate (deer, rabbits,...) store vitamin D in fat and body tissue long enough to get to Spring?

• Do mammals which burn fat during hibernation (bears, ground squirrels, ...) get vitamin D from their fat as well?

  • Interesting: Vitamin D2 in bears is higher in winter than in summer

• Some animals eat dried grass in the winter

  • Sun-cured hay has 2,000 IU per kg - "Vitamin D is the only nutrient more abundant in dried forage than in fre

• Many animals (which do not migrate) add fat in the summer - when vitamin D happens to be available

Humans unfortunately typically add fat in the winter - when vitamin D is usually NOT available

This gives one possible reason that evolution (in humans and many animals) caused the storing of vitamin D in fat

Burning fat for energy during the winter also releases vitamin D

• Vitamin D levels increased when senior women lost weight – July 2011