Getting Vitamin D From The Sun Is Actually A Lot Harder Than You Think

Basically, when your skin is exposed to the sun, the UV rays cause it to transform provitamin D3 (or 7-dehydrocholesterol) into previtamin D3, which then enters circulation, where it becomes converted to 25-hydroxyvitamin D3 (in the liver), or 25(OH)D, the form of vitamin D your doctor can measure via a blood test to assess your D status situation.

From there, the kidneys and a variety of target tissues turn that 25(OH)D into 1,25-dihydroxyvitamin D3 (1,25(OH)2D), aka calcitriol, the biologically active hormone form of vitamin D, which then performs all sorts of critical duties throughout the body, including regulating calcium and phosphorous homeostasis, promoting bone health, modulating immune function, and more.*

All in all, the process feels a teeny bit reminiscent of photosynthesis, doesn’t it? (OK, it might not be a truly legit comparison, but definitely reminds us how intelligent and sophisticated our bodies are, right?) And how systemically important this fat-soluble micronutrient is for our whole-body health.*