Hi Jenny, I used to get a big worsening of symptoms in Autumn every year, But I fixed it with Vitamin D and Magnesium, but had to take very high doses of Vitamin D to fix it 50,000 iu a week for 12 weeks (this has to be done with a Doctors supervision) and I still take up to 5000 iu a day when the sun isnt shining. It also greatly improved and in some cases got rid of a lot of my symptoms. Unfortunately a lot of stupid doctors never thought that Vitamin D might be the cause of my autumn crashes, and I had to put up with it for almost twenty years, before I found out about it on the net and got it fixed.
The reference ranges used in labs for Vit D at the moment have been proven to be way lower than they should be, so a lot of people arent getting given enough supplementation to fix the problem. There a good article about it here
http://www.thorne.com/altmedrev/.fulltext/13/1/6.pdf
If your Vitamin D levels dont go up with treatment the most likely cause is a magnesium deficiency see
http://www.vitamindcouncil.org/news-...ds-co-factors/ if you get symptoms from taking more Vit D like the ones mentioned in this article the cause is normally a magnesium deficiency
http://www.vitamindcouncil.org/about...ors/magnesium/ theres a lot good information on the vitamin D council web site.
Theres an interesting article on how vitamin D is crucial for the immune system to work properly here
http://www.sciencedaily.com/releases/2010/03/100307215534.htm I havent had an infection since getting my Vitamin D up to the correct levels, it also completely fixed my asthma.
If you can get your vitamin D tested and then find a doctor who will help you get your levels up to those mentioned in the first article, (it should be between 40- 70 ng/mL year round) you may find it fixes the problem, it worked for me.
All the best