I went to a doctor in August who suggested that I have my Vitamin D level checked. She seemed fairly confident that my level would be low given my lack of regular sun exposure and my diligence with sunscreen. While the average adult only needs 15-20 mins of sun/day without sunscreen to meet their vitamin D requirements, I routinely have no sun exposure and certainly not that much without sunscreen. In fact, ever since my dermatologist told me last year that I have “multiple risk factors for skin cancer”, I’ve been probably even more careful than previously. Anyhow, I got my level checked and it was indeed low: 23 ng/mL (normal = 33-100). While I wasn’t low enough to be classified as “severely deficient” (<15), this result concerned me. First of all, at the time I was tested I was taking 265% of the RDA or 1060 IU on an almost daily basis. Secondly, I was tested at the end of the summer which is the month of peak Vitamin D levels in most people.
Since then I’ve read a fair amount about the importance of Vitamin D in cancer prevention, depression, athletic performance, osteoporosis, and a host of other health issues, and I decided that this is something that I wish one of my doctors had brought up earlier. Realistically, I’ve probably been low my entire life and certainly for at least the last 10 years that I’ve been studying and working in the northern parts of the U.S. When in my adult life have I ever gotten that much sun? And between November and February the sun that hits the northern U.S. isn’t potent enough to create enough Vitamin D!
The wikipedia entry on Vitamin D is pretty thorough, as was the Mayo Clinic’s information, and the NYTimes’ excellent Well Blog had a post in late September which featured many helpful comments from doctors who treat low vitamin D levels (and a variety of other vitamin D enthusiasts). My chief concern in supplementation was overdoing it, since fat soluble vitamins like vitamin D can be toxic if levels are too high. I found a fair amount of evidence that it would be hard to make myself toxic. Most toxicities occur when people ingest >40,000 IU/day and the human body naturally makes up to a maximum of 10,000 IU/day. While the current maximum RDI is 2,000 IU, that guideline is apparently up for revision in 2010 and expected to be lifted to 10,000 IU.
Long story short, after reading everything I could get my hands on, I’ve started taking ~3000 IU/day and an additional 10,000 IU once/week. One point of advice that I found particularly helpful is that once you’ve supplemented for 8 weeks you should be retested and adjust as needed – pretty logical. I expect I’ll probably have to increase further to get to a target level of 50-80 ng/mL, but if I’ve been low for 10 years or more I figure I can wait and see.
If you live anywhere except New York state (figures!) you can order a home-testing kit for $65 if your doctor won’t test or your insurance won’t cover it. Remember, you want to be tested for 25-hydroxyvitamin D, also called 25(OH)D, not 1,25-dihydroxy-vitamin D, which is calcitriol.
