A scientific research team led by a University Of Alabama physician studied 29,368 women between the ages 55 to 69 to determine whether the intake of vitamin D affects ones chances of developing Rheumatoid Arthritis. Rheumatoid Arthritis is a chronic inflammatory disease that primarily affects the joints and surrounding tissues. The findings from the analysis showed that older women who consumed the most vitamin D from either diet or supplements had the lowest risk of developing Rheumatoid Arthritis. In the conclusion statement about the analysis, the researchers imply that additional research be conducted to confirm their findings. For more information go to the Journal Arthritis & Rheumatism, Vol 50, Jan. 2004

this really is an excellent long study & involves enough people to seem quite valid to me. A Calcium supp which has both vit-D and magnesium to help absorption and form bones is important.Then just getting out in the sunshine for 20 minutes a day without sunscreen gives the body what it needs to make its' own vit-D (if everything is working well).
I think it also helps to lessen pain. The body needs so much to get back into an alkaline state and be healthy. The real reason they put Vitamin D in your Calcium Sup. is to help assimilate the calcium to the blood and cells more quickly. The Magnesium is added because calcium by it's self will do what we call clump and cause constipation. Magnesium is a natural laxative.