No mention of vitamin D in this article, but:

1. Many studies which show the synergy between Magnesium and vitamin D
2. Many many studies show increasing vitamin D decreases Diabetes.
3. Magnesium increases vitamin D, which then decreases Diabetes

Article in Diabetes Health - Oct 22, 2010

Highlights

• 4500 people
• followed for 20 years
• Those getting 200 mg/1000 calories were 47% less likely to get Diabetes, than those getting only 100 mg

See also at VitaminDWiki

• Overview Magnesium and vitamin D
• All items in category Magnesium 365 items
• Know the Importance of Taking Enough Magnesium with Your Vitamin D – July 2010
• Overview Diabetes and vitamin D
• Low Magnesium and type II diabetes – June 2012

Related categories of information in VitaminDWiki Diabetes    Magnesium 

Overview of information in VitaminDWiki   Diabetes