“Our results did not show a benefit of vitamin D supplements on kidney function,” said researcher Dr. Sun H. Kim. “About 43% of the study population was taking outside-of-study vitamin D, up to 1000 IU daily, at study entry, though. Among those who were not taking any vitamin D on their own, there was a suggestion for vitamin D lowering the amount of urine protein over time, which means that it could have a beneficial effect on kidney health.”
What role does vitamin D play in kidney health?
The researchers had more than 2,200 prediabetic adults involved in the study. Over the course of nearly three years, participants took either a vitamin D placebo or 4,000 IU of vitamin D3 every day.
“The D2d study is unique because we recruited the individuals with high-risk prediabetes, having 2-out-of-3 abnormal glucose values, and we recruited more than 2,000 participants, representing the largest vitamin D diabetes prevention trial to date,” Dr. Kim said.
The researchers learned that kidney function was fairly similar between the placebo and non-placebo groups; 30 participants in the placebo group developed kidney failure, compared to 28 participants in the vitamin D group. Ultimately, it was unclear whether the vitamin D supplement was beneficial to prediabetic consumers’ kidney function.
However, the researchers explained that some participants were taking vitamin D supplements before the study began. They noted that consumers with critically low levels of vitamin D may react differently to taking supplements than the participants did.
“The majority of the study population had sufficient blood vitamin D levels and normal kidney function,” Dr. Kim said. “Benefits of vitamin D might be greater in people with low blood vitamin D and/or reduced kidney function.”