why didn't sunshine increase vitamin D levels?

[MsMom2]

My son, who's 4, has been out in the sun almost every day all summer, but his vitamin D levels have gone from 26.6 at the beginning of June to 24.7 at the end of August.  He has been in shorts and without his shirt on, was pale in the spring, but now has a tan.  

What could be causing his vitamin D levels to stay so low with so much sun exposure?

I've read that washing the skin with soap can inhibit vitamin D production by the skin, but that's not his problem.  I've also read that the body needs certain nutrient "co-factors" to use vitamin D:  magnesium, zinc, vitamin K2, boron, and a little vitamin A.  My son eats grass-fed beef almost every day, and that's supposed to have all of those co-factors but boron.  He also eats a banana or two every day, which has some magnesium.  But he's probably not getting much boron in his diet -- he's a very fussy eater, and doesn't get many fruits or vegetables.   Except for the missing boron, I would think that he's getting enough of these co-factors so that his vitamin D levels would at least increase, even if only slowly.

We are going to have his calcium levels checked to make sure that they aren't too high since I've read that that can interfere with the skin's production of vitamin D.

My son had problems breathing due to a croupy cough (tracheomalacia) several times last winter -- whenever he got an upper respiratory infection or was exposed to irritants like auto exhaust, etc, so we would really like to try to get his vitamin D levels up.

What could be keeping his vitamin D levels low?

Does anyone have any suggestions as to why his vitamin D is not increasing?

[MsMom2]

Thanks -- osteoporosis runs in the family (me, my mother, and my sister), and I'm vitamin D deficient, so absorption issues (that might run in the family) seem a likely explanation -- except that my son is apparently not making vitamin D from the sun, which seems like a different issue.  

His pediatrician (whom we like) has been very helpful about agreeing to my requests to have his vitamin D and calcium tested, but is referring to the recent IOM recommendation for vitamin D, and suggesting that it's probably not very important to get his vitamin D levels up.  A dietician at the practice did recommend supplementing with 400 IU/day over the summer (which doesn't seem like much to me), but we got my son out in the sun so much that we didn't bother with the supplements...

Can anyone recommend a doctor in the upstate NY area (or anywhere nearby) who takes an interest in vitamin D issues?

[Phyllis2010]

With appropriate supplementation, his levels should increase though I've been told some people have problems absorbing vitamin D. I don't know anything about vitamin D deficiency or appropriate dosing protocols in children. Do you have a pediatrician who can help you?