Vitamin D is not a vitamin at all — in its active form it is the most powerful steroid hormone in our bodies.
Vitamin D isn’t even a nutrient! It comes from the sun, not from nutrition!
When human skin is exposed to sufficiently powerful ultraviolet (UV) radiation from sunlight, a form of cholesterol contained in our skin (“7-dehydrocholesterol”) is converted into the precursor of Vitamin D, called “cholecalciferol”. This is then converted by our liver into the inactive bulk storage form of vitamin D that blood tests measure (“25-hydroxyvitamin D”). Although Vitamin D is present in limited amounts in cod liver oil and some fatty fish (salmon, mackerel and tuna), it is essentially unavailable in metabolically useful quantities from dietary sources.
As we age, our skin gradually loses its youthful cholesterol and its ability to synthesize Vitamin D declines over time. Although it has not been widely studied, some reports indicate that by the age of 50, Vitamin D production has fallen to approximately 50% of its original rate, and by the age of 65 production will have fallen to just 25% of its original capability. And independent of age, the skin’s melanin pigmentation — either from natural genetic racial coloration or tanning adaptation — acts to absorb much of the sun’s visible and ultraviolet radiation. This skin darkening has the beneficial effect of protecting our skin from UV radiation damage, but at the expense of further reducing the skin’s rate and capacity for Vitamin D production. (Melanin is 99.9% efficient in absorbing the energy from ultraviolet light, converting it into harmless heat energy.)
I ran into this a while back, and I got to thinking about it, since I take 1000 IU Vit D a day. My sleep patterns have improved, so has, I feel, my memory.
I was thinking that computers have caused me to stay indoors too much, and I’m not getting the Sun’s effects.
1000IU daily seems to be the new minimum recommended amount. For adults, that is.
Well, that settles it. Tomorrow afternoon, I’m taking a book and a chair to the back yard. It’s supposed to be nice and sunny.