Vitamin K supplementation and arterial calcification in dialysis: results of the double-blind, randomized, placebo-controlled RenaKvit trial

Double-blind, randomized, placebo-controlled trial in adult patients receiving maintenance dialysis at multiple centers in Denmark. In the vitamin K arm, 24 participants were randomized and serial measurements were collected at baseline, year 1, and year 2.

Oral vitamin K2 as menaquinone-7 (MK-7), one daily tablet containing 360 mg, taken every morning with some dairy fat for 2 years. The active regimen was compared with placebo in a double-blind trial.

Vitamin K2 supplementation improved vitamin K status but did not significantly slow arterial calcification over 2 years. In the vitamin K arm, serum MK-7 increased progressively and was 40-fold higher than placebo at year 2, while plasma dp-ucMGP was 40-45% lower than placebo and PIVKA-II was lowered by about 45%. Despite these biomarker effects, carotid-femoral PWV, CAC, CVC, and AAC did not differ significantly versus placebo, and calcification progressed in both groups. The adjusted year 2 between-group difference in cfPWV was 1.1 m/s (95% CI -0.1 to 2.2; P = 0.07).

The trial was small and had substantial attrition, with marked loss to follow-up by year 2 and very small analyzable samples for imaging outcomes. These missing data limited power to detect modest effects on vascular calcification and increase imprecision. Findings are also specific to dialysis patients in a Danish multicenter setting.