Vitamin D, Or: You're Not Getting Enough Sun
Over the past few months I’ve been hearing more and more about vitamin D deficiency. Then a few weeks ago Steve Gibson, the guy who does the Security Now podcast, took a rare diversion from security to talk about vitamin D (podcast here). He created a page about vitamin D explaining everything and citing all the research he’s read, and that page also links to some good videos on the topic: a 90-second video focused on cancer; another 90-second video on cancer and sun exposure; a 6-minute video on vitamin D’s effect on general health (money quote: people who take sufficient vitamin D supplements just don’t get sick anymore); and finally a 1-hour video full of tons of vitamin D science.
Certainly watch the 2-3 shorter videos, and watch the longer one if you have time. But the bottom line is this: many and probably most people are vitamin D deficient, especially in the winter months; and vitamin D deficiency is linked to not only many forms of cancer but also autism, bone diseases, tuberculosis, psoriasis, and many other diseases. And in particular, vitamin D deficiency during pregnancy and after birth can cause lots of problems for babies, most famously the disease rickets.
Crucially, vitamin D is not actually a vitamin at all; it’s a hormone. So it’s impossible to get a sufficient amount of vitamin D from your diet, unlike most real vitamins. The only way to get sufficient vitamin D is from the sun, or via supplement -- but a multivitamin will not give you nearly enough. For example, in milk that’s fortified with vitamin D, and in most multivitamins, there’s only a few hundred IU of vitamin D, whereas 10-20 minutes of noontime sun exposure will cause your body to create around 10,000 IU of vitamin D.
The problem is that in recent decades, due to the problem of skin cancer caused by overexposure to the sun, we have massively overcorrected, with the scientific, medical, and governmental guidelines generally recommending that we avoid the sun entirely, never being exposed to it without sunblock. But since sunblock blocks virtually all UVB, your body doesn’t make any vitamin D when you’re covered in sunblock.
The solution is to get a moderate amount of noontime sunlight on a daily basis. As mentioned above, just 10-20 minutes will boost vitamin D levels into the healthy range, and will not give you a sunburn. It must be within about 2 hours of solar noon though -- which is 1 PM in the northern hemisphere -- because outside that range, the sun’s angle in the sky forces it to travel through much more atmosphere, which totally blocks UVB outside of about 10AM-4PM. That’s also the reason it’s much harder to get a sunburn except within a couple hours of solar noon.
But during the winter, unless you live very close to the equator, the sun’s angle again prevents it from delivering enough UVB to generate healthy amounts of vitamin D in your skin. Because of this, and because you can’t get sufficient vitamin D via diet, I plan to start taking a vitamin D supplement soon; Steve Gibson’s vitamin D page has his recommendations about halfway down the page, and in terms of dosage it appears that 2000 IU/day is a good amount. And that’s about an order of magnitude below the level at which toxicity begins to become an issue.
This topic fascinates me partly because of its obviousness: for all of human history we’ve been exposed to at least some sun nearly every day, so the idea that we should now suddenly start avoiding it altogether is just insane. It appears that we’re now suffering many unintended consequences of that advice. There are lots of interesting statistics in the videos above, but one that sticks out to me is that, for some forms of cancer, vitamin D deficiency causes a doubled risk of metastases and a 75% increased risk of mortality.