The ViKTORIES trial: A randomized, double‐blind, placebo‐controlled trial of vitamin K supplementation to improve vascular health in kidney transplant recipients

Randomized, double-blind, placebo-controlled trial in adults with a functioning kidney transplant for at least 1 year. Forty-five participants were assigned to the vitamin K arm and 45 to placebo at a single center in Scotland, United Kingdom.

Oral vitamin K was given as 5 mg menadiol diphosphate three times per week on Monday, Wednesday, and Friday for 12 months. The comparison group received placebo.

Vitamin K did not improve vascular stiffness or vascular calcification over 12 months in kidney transplant recipients. For the primary endpoint, ascending aortic distensibility at 12 months was similar between groups, with an adjusted treatment effect of -0.23 (95% CI -0.75 to -0.29; p = .377); the multiple-imputation estimate was -0.19 (-0.71 to -0.32). The vitamin K group changed from 2.7 to 2.5 x10^-3 mmHg^-1, while placebo changed from 2.9 to 2.7 x10^-3 mmHg^-1. The authors concluded that improving vascular health in this population will likely require a multifaceted approach.

The trial was modest in size, single-center, and limited to 12 months of follow-up, which reduces power to detect smaller or longer-term effects. The transplant population was heterogeneous, which may limit generalizability and make subgroup effects harder to detect. Secondary vascular calcification outcomes were also not improved, but detailed effect estimates were limited in the extracted data.