Now about this Vitamin D deficiency. Foolish doctors aside, it's something I need to address. This requires knowledge; I'm not really into the "take a pill and hope it gets better" methodology.
We make Vitamin D3 in our skin, so long as we see the sun every now and then. It's this crazy complex process, of course; nothing in nutrition (or human chemistry, for that matter) is ever simple. When UVB radiation from the sun hits our skin, it's sort of a catalyst for a reaction that uses a derivative of cholesterol (yup) to make cholecalciferol, the first stage of D3. (Interesting: this takes about 12 days from the time of sun exposure.) The cholecalciferol is then converted (hydroxylated, if you must know) in the liver to become calcidiol, which is the "circulating" form of D3. The calcidiol is then again hydroxylated in the kidneys to form calcitriol - the final, "biologically active" form of D3 (a.k.a. what the body actually uses).
Apparently about 2/3 of the U.S. population doesn't get enough Vitamin D. This is totally hearsay (my doc said it, and my chiropractor called it an epidemic; I haven't substantiated that number in any way). But after I got my deficient news of course I did some research, and I came across many papers stating that most people don't get enough, and that the RDAs are probably way too low. Sure, there are foods that are fortified, but most of them have minimal amounts, and some contain D2 which is far less useful to the body. Seems that "Scientists" are counting on us getting out into the sun.
Which makes sense. The D3 that we make ourselves is far more abundant, and more potent, than anything we can swallow in food or pills. But of course we can only produce it when we get sunny - which we're all terrified to do thanks to tireless efforts of skin care companies and overblown news reports. Sun "protection" isn't just for the beach anymore: these days we have SPFs in our lip balms and our hand and facial creams. We've been told we must put on sunscreen before setting foot outside - thus giving ourselves no chance whatsoever to create any Vitamin D. (Frighteningly, failing to reapply often enough may create free radicals that could actually increase risk of cancer. Not to mention that some sunscreens don't block UVA radiation, which also contributes to skin cancer. When considering information about these products, be sure to separate fact from marketing.)
Skin cancer is of course a valid concern. But I don't accept the reasoning that because extremely high doses of an agent can be carcinogenic, the answer is therefore to remove that something completely. Clearly, our bodies are meant to absorb and use sunlight. We are simply not meant to bake in it all day long. This isn't so hard to figure out. Those of us who are the most fair do the poorest when exposed to the sun - and, interestingly, need the least exposure to sunlight to produce adequate amounts of Vitamin D. People with higher concentrations of melanin can spend longer times in sunlight without ill effects, and also need longer exposures to produce Vitamin D. Coincidence? Unlikely.
So my conclusions are pretty much the same as when I come upon any controversy. The answer is in moderation. Spend some time in the sun, but not so much that you'd end up with a sunburn without protection. That's my plan anyway. My hope is to spend between ten and 30 minutes getting some sunlight, at least on my hands and face, every day that it's sunny. (They say hands and face is enough. You know, "the they.") Because I'm so far down, I'm also supplementing. I won't go out in the hottest part of the day, which tends to be around 3-4pm - I'm usually at work then anyway.
As long as it's not raining, I'll go out on cloudy days too. Apparently cloud cover cuts UVB to about 60% of its normal strength - so it's still possible to benefit from the sun when it's not sunny. (This also means that if you're planning to be out and exposed all day, maybe a little protection would be a good idea for the very fair skinned even if it is cloudy.) Clouds also tend to cut down on the heat pretty efficiently, so if the day is nice otherwise and I feel alright, maybe I can stay out for longer. :)
As with so many things, it's about using some common sense and doing what is most appropriate for my body. At the end of the day, what else is left?