Rinkoo Dalan at Tan Tock Seng Hospital in Singapore and colleagues conducted a study to see if vitamin D supplementation could improve endothelial function in type 2 diabetes mellitus patients.  

For the study, diabetes mellitus patients with lower than 20 ng/mL of serum vitamin D or 25(OH)D were asked to take 4000 IU of cholecalciferol per day and those with having 20 to 30 ng/mL of vitamin D in their blood took 2000 IU of cholecalciferol per day.  The supplementation lasted 16 weeks.  

As a result, vitamin D supplementation was found to improve endothelial function in type 2 diabetes mellitus patients.  

Comment:  Even if vitamin D does not improve endothelial function, patients or healthy individuals should make sure they have enough circulating vitamin D.  One cannot afford to suffer vitamin D deficiency, which has been linked to a range of health conditions inkling many types of cancer, depression, diabetes mellitus, arthritis, heart disease, and infections. (David Liu)

Rinkoo Dalan, Huiling Liew, Pryseley Nkouibert Assam, Edwin SY Chan, Fahad Javaid Siddiqui, Alvin WK Tan, Daniel EK Chew, Bernhard O Boehm, Melvin KS Leow, A randomised controlled trial evaluating the impact of targeted vitamin D supplementation on endothelial function in type 2 diabetes mellitus: The DIMENSION trial, Diabetes and Vascular Disease Research May 2016 vol. 13 no. 3 192-200