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Could Omega-3, Vitamin D Supplementation Prevent CKD in Type 2 Diabetes?

November 12, 2019

New findings presented at Kidney Week 2019 indicate that supplementation with vitamin D3 and/or omega-3 fatty acids likely does not help prevent the development or progression of chronic kidney disease (CKD) among adults with type 2 diabetes.1

“The findings do not support the use of vitamin D or omega-3 fatty acid supplementation for preserving kidney function in patients with type 2 diabetes,” the authors of the study said of their findings.1

Ian H. de Boer, MD, and colleagues arrived at their conclusion after performing a randomized clinical trial with a 2 × 2 factorial design, which included 1312 adults (mean age 67.6 years) with type 2 diabetes who were recruited from all 50 US states as an ancillary study to the Vitamin D and Omega-3 Trial (VITAL). Mean estimated glomerular filtration rate (eGFR) at baseline was 85.8 mL/min/1.73 m2. Follow-up lasted until December 2017.

Participants were randomly assigned to receive 2000 IU vitamin D3 per day and 1 g omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid) per day (n = 370); vitamin D3 and placebo (n = 333), placebo and omega-3 fatty acids (n = 289), or 2 placebos (n = 320) for a period of 5 years. The primary outcome was defined as change in eGFR based on serum creatinine and cystatin C from baseline to 5 years.

Ultimately, 934 (71%) of 1312 participants completed the trial. Mean change in eGFR from baseline to 5 years was found to be -12.3 mL/min/1.73 m2 with vitamin D3 compared with -13.1 mL/min/1.73 m2 with placebo, and -12.2 mL/min/1.73 m2 with omega-3 fatty acids compared with -13.1 mL/min/1.73 m2 with placebo. The researchers observed no significant interaction between the 2 interventions.

A total of 58 participants (n = 32 receiving vitamin D3 and n = 26 receiving placebo) experienced kidney stones, and 45 (n = 28 receiving omega-3 fatty acids and n = 17 receiving placebo).

Currently, “contrasting the results of VITAL-DKD and its predecessor vitamin D trials with the impressive body of epidemiological research that implicated vitamin D deficiency in various adverse health outcomes offers a stark lesson on the chasm between association and causation,” wrote Anika Lucas, MD, and Myles Wolf, MD, MMSc, in an accompanying editorial.2

“It now seems safe to conclude that many prior epidemiological associations between vitamin D deficiency and adverse health outcomes were driven by unmeasured residual confounding or reverse causality,” they added.2

—Christina Vogt


  1. de Boer IH, Zelnick LR, Ruzinski J, et al. Effect of vitamin D and omega-3 fatty acid supplementation on kidney function in patients with type 2 diabetes: a randomized clinical trial [published online November 8, 2019]. JAMA
  2. Lucas A, Wolf M. Vitamin D and health outcomes: Then came the randomized clinical trials [Published online November 8, 2019]. JAMA
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