Taking vitamin D and fish oil supplements won’t prevent kidney disease in people with type 2 diabetes, a new study finds.
Many diabetics use the supplements, hoping they will have a positive effect on their kidneys and heart, the researchers 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,” said lead author Dr. Ian de Boer. He is a professor of medicine at the University of Washington School of Medicine, in Seattle.
The researchers hoped the supplements would be beneficial because animal studies and lab experiments had suggested that anti-inflammatory and other properties in these supplements might prevent or slow progression of kidney disease in people with type 2 diabetes.
And in humans, other research has found a link between kidney problems and low levels of vitamin D and diets lacking fish.
For the study, which was part of the nationwide Vitamin D and Omega-3 Trial (VITAL), the researchers looked at kidney function in more than 1,300 people with type 2 diabetes.
Study participants were randomly assigned to get vitamin D and fish oil supplements; vitamin D and a fish oil placebo; fish oil and a vitamin D placebo; or two placebos.
Over five years, kidney function declined an average of 15%. The decline occurred whether participants took supplements or not, the investigators found.
“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,” de Boer said in a university news release.
About 40% of the 28 million Americans living with type 2 diabetes will develop chronic kidney disease, he noted.
The study was published Nov. 8 in the Journal of the American Medical Association. It was presented concurrently at a meeting of the American Society of Nephrology, in Washington, D.C.
For more on type 2 diabetes, head to the American Diabetes Association.