We are taking D3 in our house, though not every day. I guess what I’m confused about is this: I’ve been hearing that while 15 min. a day of sun is adequate in the summer months, once late fall and winter hit, those of us north of…Georgia?…have no hope of getting enough Vit. D from sun exposure.

Hi Jess, I have the same question too, although I’d bet that there is sunshine even in winter, or maybe it breaks through the clouds enough to give us our daily dose?

@Jess I thought it was more the assumption that we don’t get outside in the cold weather, and that if we did most of our skin would be covered up? Maybe a combo?

I was tested and had levels low enough to justify a catch-up prescription. My doctor said they had been testing people for 6 months and only 2 patients did not have abnormally low levels. (I live in Chicago and saw my doctor in March)

Re. the winter thing…I could have this wrong…but my memory is that the angle of the sun to the earth at that time of year has something to do with not getting enough D in winter.

Mistress_Scorpio, I was on that same supplement when I was nursing because my blood levels were supposedly too low, and the problem was that although I took the supplement as directed for many months, the effect on my levels was negligible. At one point I had to switch doctors and I didn’t mention it to the new and she never tested me.

How an advisory body can possibly come up with blanket vitamin D intake recommendations despite widely varying sun exposure and considerable difference in ability to make vitamin D in the skin,or in absorption from the gut, totally mystifies me.The only way to get useful info is actually test serum vitamin D levels for cohorts of people at different ages with different life styles&pigmentation and at different latitudes before any valid conclusions can be made.The IOM did NONE of these things they probably just cherry picked the medical literature to validate their a priori opinions,There is no evidence whatsoever for instance that toxic D3 levels can occur even at intake levels of 10000 IU or even higher.The kidneys activate D3 precursors as required by blood calcium levels to regulate calcium absorption in the gut,and it would also take extremely high calcium intake to produce hypercalcimia&kidney stones.This is just a red herring.Since this risk is quite minimal,it is therefore perversely stupid to recommend these low levels,On top of all this they also chose to ignore all research evidence about the benefits of vitamin D administration in other diseases and exclusively focussed on bone issues,stating that there was not enough ‘evidence’.I suppose in another few decades or so they might have another stab at that.My take:Ignore these hidebound clowns,listen instead to your own doctor,he or she may have relevant clinical experience.

As I explain on my blog:

http://whyvitamind.blogspot.com/

vitamin D being involved in only bone health does not make a lot of sense. But if we take serious the evidence of it being involved also in modulating the immune system, then things become more clear. Animals may have evolved to use vitamin D to modulate processes that use a lot of energy, like the immune system. When the Sun is no longer high in the sky, that signals a coming Winter, and it makes sense to let such processes run in a more energy efficient way, so that fat reserves can be built up more easily.

The less fat an animal has to begin with the sooner its vitamin D levels will drop, as vitamin D is stored in body fat. So, this is consistent with vitamin D being used to implement an optimal strategy to make it through Winter. As vitamin D levels drop to ever lower values as Winter progresses, more energy saving measures are taken.

Getting calcium from food costs energy, due to the low concentration of calcium in food. It costs far less energy to maintain the necessary calcium levels in the blood from getting it from our bones, because the concentration of calcium there is much higher. However, this comes at the expense of maintaining the bones. If this situation lasts for a few weeks, it is not going to do significant damage; the benefits of spending less energy to digest food are much greater for animals that have to survive in nature.