The mission of the International Dark-Sky Association is “to preserve and protect the night time environment and our heritage of dark skies through quality outdoor lighting.” They’re all about stressing the importance of lighting on health, light pollution, and some really interesting stuff.
For more on the topic, check out their website, darksky.org, and Paul Bogard’s book, The End of Night: Searching for Natural Darkness in an Age of Artificial Light.
“Without leaves, without buds, without flowers;
Yet they form fruit.
As a Food, as a tonic, as a medicine;
The entire creation is precious.”
-weird mushroom poem of sketchy origin
Mushrooms: They have B12! When exposed to UV light, they make vitamin D2. Protein, fibre, and selenium. Shall I go on?
Vitamin D synthesis is TEAMWORK!
Skin: 7-dehydrocholesterol + UVB = previtamin D3.
Liver: Previtamin D3 –> 25(OH)-Vitamin D3.
Kidney: 25(OH)-Vitamin D3 –> 1,25(OH)2-Vitamin D3 if you need it or 24,25(OH)2-Vitamin D3 if you don’t.
N.B. one of the major regulatory pathways occurs in skin: if you’re getting a lot of sunlight, then skin darkens to block this step. Supplemental and dietary Vitamin D3 bypass this… but the dietary Vitamin D supply rarely produces toxicity because it’s not very abundant. In other words, sunlight Vitamin D never reaches toxic levels. Supps could (rare, but possible).
Disclaimer: I’m not against Vit D supps, but prefer sunlight whenever possible.
The other major regulatory step is in the kidney. Production of 1,25(OH)2-Vitamin D3 is tightly regulated — so blood levels don’t decline until your very deficient… so 25(OH)-Vitamin D3 is a better indicator of skin production and dietary intake.
Disclaimer #2: this post is not about any of the pleiotropic effects of Vitamin D or D supps, which range in value from worthless to helpful to possibly harmful.
For some of that stuff, see:
Vitamin D: still a scam, still immunosuppressive… by Jane Plain
The Vitamin D seminar by Ivor Cummins
Vitamin D 101 by Kris Gunnars
The Vitamin D Debacle with Ivor Cummins and Sam Feltham
all of the above are more pro-D supps than me, which I find perfectly OK.