Chronic kidney disease (CKD) is not uncommon among patients with type 2 diabetes (T2D) and can lead to other complications including end-stage kidney disease. However, few treatments are available. In a new randomized trial, researchers examined the effects of supplementation with vitamin D3 or omega-3 fatty acids compared to placebo on CKD risk in T2D patients. Type 2 diabetes patients across all 50 states were recruited between November 2011 and March 2014. This trial was an ancillary study to the Vitamin D and Omega-3 Trial (VITAL), which was conducted by a single Massachusetts-based institution. A total of 1,312 patients (mean age, 67.6 years; 46% were female) 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 two placebos (n = 320) for five years. The main outcome measure was five-year change in glomerular filtration rate estimated from serum creatinine and cystatin C (eGFR). Of the 1,312 randomized patients, 934 finished the study. Mean eGFR (SD) at baseline was 85.8 (22.1) mL/min/1.73 m2; from baseline to five-year follow-up, mean change in eGFR with vitamin D3 was −12.3 (95% CI, −13.4 to −11.2) mL/min/1.73 m2 compared to −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). Omega-3 fatty acids were associated with a mean change in eGFR of −12.2 (95% CI, −13.3 to −11.1) mL/min/1.73 m2 (difference versus placebo, 0.9 [95% CI, −0.7 to 2.6] mL/min/1.73 m2). Fifty-eight patients developed kidney stones (vitamin D3, n = 32; placebo, n = 26); 45 sustained gastrointestinal bleeding (omega-3 fatty acids, n = 28; placebo, n = 17). “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 researchers concluded.