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Original Investigation
November 8, 2019

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

Author Affiliations
  • 1Division of Nephrology, Department of Medicine, University of Washington, Seattle
  • 2Kidney Research Institute, University of Washington, Seattle
  • 3Puget Sound VA Healthcare System, Seattle, Washington
  • 4Division of Preventive Medicine, Brigham and Women’s Hospital, Boston, Massachusetts
  • 5Department of Laboratory Medicine, University of Washington, Seattle
  • 6Department of Biomedical Sciences, Cedars-Sinai Medical Center, Los Angeles, California
  • 7Harvard T. H. Chan School of Public Health, Boston, Massachusetts
JAMA. Published online November 8, 2019. doi:https://doi.org/10.1001/jama.2019.17380
Key Points

Question  In adults with type 2 diabetes, do vitamin D or omega-3 fatty acid supplements help prevent development or progression of kidney disease?

Findings  In this 2 × 2 factorial randomized clinical trial that included 1312 participants with type 2 diabetes, there was no significant difference in the change in estimated glomerular filtration rate at 5 years with vitamin D3 supplementation vs placebo (−12.3 vs −13.1 mL/min/1.73 m2) or with omega-3 fatty acid supplementation vs placebo (−12.2 vs −13.1 mL/min/1.73 m2).

Meaning  These findings do not support the use of vitamin D or omega-3 fatty acid supplementation for preserving kidney function in adults with type 2 diabetes.

Abstract

Importance  Chronic kidney disease (CKD) is a common complication of type 2 diabetes that can lead to end-stage kidney disease and is associated with high cardiovascular risk. Few treatments are available to prevent CKD in type 2 diabetes.

Objective  To test whether supplementation with vitamin D3 or omega-3 fatty acids prevents development or progression of CKD in type 2 diabetes.

Design, Setting, and Participants  Randomized clinical trial with a 2 × 2 factorial design conducted among 1312 adults with type 2 diabetes recruited between November 2011 and March 2014 from all 50 US states as an ancillary study to the Vitamin D and Omega-3 Trial (VITAL), coordinated by a single center in Massachusetts. Follow-up was completed in December 2017.

Interventions  Participants were randomized to receive vitamin D3 (2000 IU/d) and omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid; 1 g/d) (n = 370), vitamin D3 and placebo (n = 333), placebo and omega-3 fatty acids (n = 289), or 2 placebos (n = 320) for 5 years.

Main Outcomes and Measures  The primary outcome was change in glomerular filtration rate estimated from serum creatinine and cystatin C (eGFR) from baseline to year 5.

Results  Among 1312 participants randomized (mean age, 67.6 years; 46% women; 31% of racial or ethnic minority), 934 (71%) completed the study. Baseline mean eGFR was 85.8 (SD, 22.1) mL/min/1.73 m2. Mean change in eGFR from baseline to year 5 was −12.3 (95% CI, −13.4 to −11.2) mL/min/1.73 m2 with vitamin D3 vs −13.1 (95% CI, −14.2 to −11.9) mL/min/1.73 m2 with placebo (difference, 0.9 [95% CI, −0.7 to 2.5] mL/min/1.73 m2). Mean change in eGFR was −12.2 (95% CI, −13.3 to −11.1) mL/min/1.73 m2 with omega-3 fatty acids vs −13.1 (95% CI, −14.2 to −12.0) mL/min/1.73 m2 with placebo (difference, 0.9 [95% CI, −0.7 to 2.6] mL/min/1.73 m2). There was no significant interaction between the 2 interventions. Kidney stones occurred among 58 participants (n = 32 receiving vitamin D3 and n = 26 receiving placebo) and gastrointestinal bleeding among 45 (n = 28 receiving omega-3 fatty acids and n = 17 receiving placebo).

Conclusions and Relevance  Among adults with type 2 diabetes, supplementation with vitamin D3 or omega-3 fatty acids, compared with placebo, resulted in no significant difference in change in eGFR at 5 years. 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.

Trial Registration  ClinicalTrials.gov Identifier: NCT01684722

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