Oh boy, have you opened up a great topic! YES! Vitamin D deficiency is very common in both EDS and MS, and heaven knows what other neurological conditions. In the MS world, patients take as much as 10,000 units per day. It took me a long time to get up to normal levels, but I finally did. Our son’s actually went a bit too high, and we had to back down (oops). Now that my fingernails are becoming funky (flattened, longitudinal ridging, some curling under, some white spots), I know there are certain vitamins/minerals I’m not absorbing well. Heaven knows I have more supplements in my body than the Sunday paper (ha), but absorption seems to be an issue. Because Vit. D is an anti-inflammatory, a lot of folks are jumping on the vitamin de jour (guilty!).