What a difference a D makes

It’s winter. The sun is setting at 4:30.  Not that those of us who live in the Northwest would know when the sun sets.  Or rises.  It’s all Fifty Shades of Gray here.  Slate gray dawn, flannel gray morning, feather gray noon, battleship gray afternoon.  You get the idea:  No sun.  No sun means, even for those of us crazy Northwesterners who spend day"light" time outdoors in the soggy winter, very little vitamin D.Fast primer on vitamin D:  It’s the one vitamin we mammals can actually make.  Our skin synthesizes it (from cholesterol!) when we are “adequately” exposed to sunlight.  You’ll remember from high school science class that D is “good for the bones” and that “deficiencies are rare.”  But “deficiency” in the vitamin world is most often defined as the level at which you would see harm – in the case of deficient D that would be developing rickets.  Your vitamin D level could be quite low (significantly below optimum or counterclockwise/ anti-aging levels) without being “deficient.Here’s why I’m writing about vitamin D today:  A new study from the International Food Information Council identifies wide disparities between what people (1,000 U.S. adults) think they are getting, vitamin-wise, and what they are really getting.  So 68 percent think they are getting sufficient vitamin D…but actually, only 32 percent are meeting the recommended intake.  (The disparity is most stunning with fiber, by the way, with 2/3 thinking they get enough of it, but actually less than 5 percent meeting the recommendation.)  Most people in the northern hemisphere – not just the Northwest – cannot count on producing enough “sunshine vitamin,” as D is commonly called, by themselves. And getting enough from food is harder than you might think.  A glass of fortified milk , one of the best sources, provides less than a tenth of  what you need.But that’s not the main reason I’ve chosen to write about D today.  The main reason is the new research that shows a link between adequate amounts of D in the blood and our body’s ability to maintain healthy blood glucose levels.  Stay with me here.  High blood glucose levels have long been linked to increased risk of diabetes.  Now there’s research linking elevated blood glucose levels to increased risk of dementia and Alzheimer’s.  It looks like vitamin D may be much more important in healthy aging and counterclockwise strategies than we originally thought.Of course you don’t want to forget the well established vitamin D/ bone connection. (Osteoporosis is not a good thing).  Without enough vitamin D, our bodies can’t make use of the calcium we consume – no matter how much calcium-rich foods we eat or how many supplement pills we pop.So, on these sunless days, take a moment to re-think your vitamin D intake.What’s enough?  Good question.  RDA for mid-lifers is 600-700 IU (international units), but most experts think this is way too low. More is better.  Maybe a lot more.  The Tolerable Upper Intake Level for vitamin D, the level beyond which there might be safety concerns, is 4000 IU.  I take 2000 IU a day, even on those rare and wonderful winter days when the sun appears in the skies above western Oregon.