Vitamin D and omega-3 of no benefit in diabetic kidney disease finds JAMA Study

USA: Refuting the beneficial role of vitamin D supplements for type 2 diabetes patients, the researchers have found that supplements of vitamin D and omega-3 fatty acids do nothing to improve kidney function in T2D patients.

The study, published in the journal JAMA, is the largest clinical study to date of the supplements in this patient population. The results, presented concurrently at the American Society of Nephrology conference in Washington, D.C., do not support the use of vitamin D or omega-3 fatty acid supplementation for the preservation of kidney function in T2D patients.

Chronic kidney disease (CKD), a common complication in type 2 diabetes, is a condition in which the kidneys are not able to adequately remove waste and fluid from the body. It disrupts a person's health in various ways ultimately leading to kidney failure and is associated with a high cardiovascular risk. Only a few treatments are available for CKD prevention in T2D patients.

Ian H. de Boer, professor of medicine at the University of Washington School of Medicine, and colleagues tested whether supplementation with vitamin D₃ or omega-3 fatty acids prevents the development or progression of CKD in type 2 diabetes.

"We were hopeful for both of these interventions, vitamin D and fish oil, but they don't appear to be particularly effective for this purpose," said de Boer.

Previous animal-model and cell-culture studies have suggested that vitamin D and fish oil supplements have anti-inflammatory and other properties that might prevent or slow type 2 diabetes' progression to chronic kidney disease. Research also has found associations between humans' kidney decline and lower levels of vitamin D and lower dietary intake of fish.

"A lot of people use the supplements hoping there are beneficial kidney and cardiovascular effects," de Boer said. "We wanted this study to clarify whether these supplements have any real kidney benefit in adults with diabetes. Even if it's not the result we hoped for, closing a chapter is useful for patients and clinicians and researchers alike."

The trial, conducted as part of the nationwide Vitamin D and Omega A-3 Trial (VITAL), involved 1312 adults with type 2 diabetes recruited between November 2011 and March 2014 from all 50 US states. The 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.

Participants submitted blood and urine samples to establish a baseline estimated glomerular filtration rate - eGFR, a measure of the kidneys' waste-filtering performance - and the presence of protein in the urine.

Key findings of the study include:

• 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 mL/min/1.73 m² with vitamin D₃ vs −13.1 mL/min/1.73 m² with placebo (difference, 0.9 mL/min/1.73 m²).


• Mean change in eGFR was −12.2 mL/min/1.73 m² with omega-3 fatty acids vs −13.1 mL/min/1.73 m² with placebo (difference, 0.9 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).

"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," wrote the authors.

More Information: "Effect of Vitamin D and Omega-3 Fatty Acid Supplementation on Kidney Function in Patients With Type 2 Diabetes -- A Randomized Clinical Trial" published in the journal JAMA.