I started taking Vitamin D3 when I noticed a pattern with my health. Over the years, I tend to decline starting in October and then get better in May. I don’t know if this is vitamin D related, but even in Florida, the angle of the winter sun keeps us from getting as many hours of the type of direct rays needed to make D. I also have a VDR snp that may affect my ability to utilize vitamin D. So in the winter I take about 8,000IU of D3 daily and then in the summertime, I take about 4,000IU daily. While on this regimen, my blood work shows about the same amount of vitamin D in both seasons, around 40ng/ml, – right in the mid-range, so it’s probably not hurting anything and possibly helping with immunity and reduction in inflammation.
Here are some of the many studies of the interaction between vitamin D3 and immune function:
Illuminating vitamin D effects on B cells – the multiple sclerosis perspective ~ (ME is similar to MS in that it is a neuro-immune disease with similar symptoms)