Seattle, WA is a beautiful place to live, and for those of us that live here the overcast days and periodic rain is nothing new to our everyday routine. We have come to embrace the cloudiness and accept that in the winter most activities will take place in-doors. With this shift into our warm and dry homes and automobiles, along with the cloudy skies, we greatly reduce our exposure to the sun. While dermatologists everywhere are celebrating this, our general practitioners and cringing when they see our blood tests that inevitably say we are dangerously low in vitamin D.
The term "vitamin D" refers to several different forms of this vitamin. Two forms are important in humans: ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). Vitamin D2 is synthesized by plants, and Vitamin D3 is synthesized by humans in the skin when it is exposed to ultraviolet-B (UVB) rays from sunlight. Foods may be fortified with vitamin D2 or D3.
Vitamin D is essential for promoting calcium absorption in the gut and maintaining adequate serum calcium and phosphate concentrations to enable normal mineralization of bone and prevent hypocalcemic tetany. It is also needed for bone growth and bone remodeling by osteoblasts and osteoclasts. Without sufficient vitamin D, bones can become thin, brittle, or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults. Together with calcium, vitamin D also helps protect older adults from osteoporosis.
What does all that mean? Basically vitamin D is a very important vitamin to have circulating around in our systems. Without vitamin D we are unable to absorb calcium, which causes our bones to become brittle. This is why milk is now fortified with vitamin D, to promote the absorption of the calcium in milk!
Now, all this talk about not getting enough vitamin D makes us want to run to the drug store and buy multivitamins, right? Well, there are a few things we need to know first. Vitamin D is a fat-soluble vitamin, meaning it is possible to have too much, but recently research has been challenging the current tolerable upper limit (UL). Due to this, I am not going to state the amount you should be getting, but here is a link to one of the articles on it, feel free to do a little research yourself [Research Link]. I also encourage you to ask your general practitioner their advice on the topic, but either way put some thought into your vitamin D intake!
References
http://dietary-supplements.info.nih.gov/factsheets/vitamind.asp
http://www.mayoclinic.com/health/vitamin-d/NS_patient-vitamind
