A family member was feeling chronically tired, unusual for someone of her age and apparent health. Suspecting anemia, the doctor did some blood tests. Lo and behold, her iron levels were fine—but she was deficient in vitamin D! From what I've heard, that's not unusual for Americans, especially those who live in the northern parts of the country. I grew up knowing that vitamin D was important for preventing rickets, a disease I had mentally relegated to history, like smallpox and scurvy. (I actually thought about smallpox more frequently than rickets, since I am of the last generation to receive routine smallpox vaccinations.) However, it turns out that vitamin D is essential for a lot more than that, including a healthy immune system. As with nearly everything health-related these days, there's controversy over how much is needed, but one thing is clear: many of us are deficient, and could safely use a lot more than we are getting now.
I find it interesting that the tests my doctor orders for every annual exam, which check my blood for multitudinous levels of this and that, do not include measures of vitamin D, or any other vitamin for that matter. Not that I'm worried about D in particular, given that we live in Florida. There's no doubt in my mind that the best way to obtain vitamin D is through exposure of our skin to the sun (don't tell my dermatologist I said that), not only because it is the most natural (there are not many un-fortified food with a lot of vitamin D), but because sunlight exposure produces other substances important to health, such as nitric oxide.
Let's see: For many decades, Americans have been increasingly avoiding the sun, spending nearly all our time indoors, and slathering ourselves with sunscreen when we are not. We have also been cutting down our intake of some of the best natural food sources of vitamin D: egg yolks, red meat, and liver, with fatty fish being about the only good source we're not encouraged to eat less of. (I'm certain it's not coincidental that fatty fish has throughout history been a popular food in lands where it's difficult or impossible to get sufficient vitamin D through sun exposure.) It's no wonder that we have a hidden epidemic of vitamin D deficiency!
I've always wondered why breast milk is apparently deficient in vitamin D, which is why babies who don't get fortified formula are routinely prescribed supplements. It doesn't seem right that the system designed for a baby's best nutrition should be so lacking. I can think of two possibilities: (1) mothers are themselves deficient, and thus can't provide what their babies need, and/or (2) in cultures with sufficient sunlight, babies have for millennia spent a great deal of time outdoors, naked or nearly so, and thus would be making their own vitamin D.
Florida is a good place for getting all the sun exposure we need. However, we too spend most of our time indoors, and shouldn't be complacent. When it was recommended from a couple of independent sources, I decided to download the dminder app on my phone. It's pretty simple, and lets me keep track of my vitamin D intake, from food, supplements, and exposure to the sun. In my case, the first two pale in comparison with the last, at least at this time of year.
Taking into account skin tone, clothing, weather, latitude, elevation of the sun, and time of exposure, dminder calculates approximately how much vitamin D I'm making through my skin for each exposure session (at least those for which I remember to start the app).
A few interesting observations:
- For the purpose of making vitamin D, there's no point to sunbathing except between the hours of 8:56 a.m. and 5:54 p.m., because the elevation of the sun is not sufficient at other times. (The hours change, of course, with latitude and the changing of the seasons.)
- Solar Noon at the moment is actually 1:25 p.m., thanks to our propensity for meddling with the clocks.
- In the present season, during which I wear shorts and a t-shirt, in the middle of the day I can easily generate 2000 IU's of vitamin D during a mere 25-minute walk around the neighborhood!
I will be interested to see what dminder has to say about the summer sun in New England.
