Ian H. de Boer, MD, MS, is among a number of researchers currently seeking inexpensive, safe, and accessible interventions to prevent CKD in patients with diabetes. With experimental and observational studies reporting that vitamin D3 and omega-3 fatty acids may help prevent CKD in patients with type 2 diabetes. Dr. de Boer and colleagues conducted a randomized clinical trial—published in JAMA—to test this possibility.

The trial was a sub-study of the Vitamin D and Omega-3 Trial (VITAL), with a two-by-two factorial design. Between 2011 and 2014, more than 1,300 participants with type 2 diabetes were recruited from all 50 states. Participants were randomly selected to receive vitamin D3 (2000 IU/d) and omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid; 1 g/d), vitamin D3 and placebo, placebo and omega-3 fatty acids, or 2 placebos for 5 years. Participants collected blood and urine samples locally and mailed them overnight for laboratory assessment of the effects of vitamin D3 and omega-3 fatty acids on kidney function and damage. Follow up was conducted in 2017.

The results indicate that neither vitamin D3 nor omega-3 fatty acid supplementation slowed the loss of kidney function. The mean change in glomerular filtration rate estimated from serum creatinine and cystatin C (eGFR) from baseline to year 5 was −12.3 mL/min/1.73 m2 with vitamin D3, compared with −13.1 mL/min/1.73 m2 with placebo. Similarly, mean change in eGFR was −12.2 mL/min/1.73 m2 with omega-3 fatty acids, compared with −13.1 mL/min/1.73 m2 with placebo. Similar numbers of patients in the placebo and vitamin D3 groups developed kidney stones, whereas slightly more patients receiving omega-3 fatty acids experienced gastrointestinal bleeding when compared with those receiving placebo.

“Our findings do not support routine supplementation of vitamin D3 and omega-3 fatty acids to help prevent CKD in patients with type 2 diabetes,” notes Dr. de Boer. “A number of recent vitamin D trials have shown a lack of benefits. This study is in line with those results, suggesting it’s best to turn our attention toward other approaches to prevent and treat diabetic kidney disease.”


Effect of Vitamin D and Omega-3 Fatty Acid Supplementation on Kidney Function in Patients With Type 2 Diabetes: A Randomized Clinical Trial