Gordon - It's interesting you mention the yin and yang. The many beneficial effects of vitamin D are amazing. I'm a big supporter of supplementing year-round with increased dosing in the 'grey' months here in NE Ohio starting in September and resume lower dosing in early May.
As we age, we lose the ability to convert the sunshine effects of vitamin D in our skin to that which functions therapeutically in the body. My levels were very low (18) when initially tested even though I spent a lot of time in the summer sun without sunscreen other than on my face ( I always burned easily since I have the blond, fair-skin complexion). Now that my vitamin D levels are consistently between 60 and 70, I find that I can spend time in the sun and not sustain any sunburn from overexposure.
The vitamin D experts talking about wide-spread deficiency being so prevalent never fail to mention that part of the problem is that everyone is cautioned never to go in the sun without screen - which defeats the sunshine source for vitamin D via the skin. The other factor they mention is that studies have never been done to see what the UV's do when they interact with the various chemicals screens contain. One speaker thought that quite likely, not only did that block vitamin D absorption and therefore production, but also
contributed to some forms of skin cancer because the chemicals are heated to high temps and remain in contact with the skin for long periods of time. They suggested that when one optimizes vitamin D, it naturally becomes protective to the skin..(within reason, obviously).
Besides skin, the other benefits of vitamin D definitely worth knowing about and taking steps to correct low test levels. I can attest personally to the muscle benefits... after suffering and treating with fibromyalgia pain for many years without success, when I began to replete with supplemental vitamin D3, my pain went away. I stopped. It came back. I resumed, pain vanished. The rheumatologist at the time was totally clueless about 25 OH D testing. The new FM MD zeroed in on that immediately.
Another huge benefit with optimizing vitamin D is enhancing the immune system. As a result, (without flu shots) I've avoided having a cold for 11 seasons and flu for 12 seasons... now in the 13th year.
A highly significant and important function of vitamin D has to do with the pancreas which which has receptors for D and when levels are optimized, people have far less tendency to develop insulin resistance and diabetes. Beta blockers caused me to become insulin resistant and again, after optimizing the D levels, I reversed that trend. My A1C levels have remained consistently good.
Everyone should be tested to learn their 25 OH D levels because you can't possibly know for sure without testing. I just learned of a woman who lived in NYC until recently... business executive, not much outdoor time. She was feeling worn out and found a holistic MD in her new retirement location. Her vitamin D level is 6. (!!!)
Jackie