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.”

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