Vitamin K Supplementation to Improve Vascular Stiffness in CKD: The K4Kidneys Randomized Controlled Trial.

Randomized controlled trial in adults with non-dialysis chronic kidney disease stage 3b or 4. The active vitamin K arm included 80 participants, and the trial was conducted in Dundee and Glasgow, United Kingdom, with enrollment from January 19, 2016 to September 20, 2017.

Oral vitamin K2 (menaquinone-7, MK-7) 400 mg once daily for 12 months, compared with placebo.

Vitamin K2 did not improve vascular stiffness or other main vascular health outcomes in adults with CKD stage 3b-4. For carotid-femoral pulse wave velocity at 12 months, the vitamin K group and placebo group were both 11.7 m/s; the adjusted treatment effect was -0.12 (95% CI -0.93 to 0.69; P=0.77). No significant differences were seen in office BP, NT-pro-BNP, augmentation index, short physical performance battery, or grip strength. Falls were less frequent by rate in the vitamin K group (0.024 vs 0.161 per month; p=0.001), but overall adverse events did not differ meaningfully and only small numbers died or started renal replacement therapy.

The trial was relatively small for detecting modest effects and was limited to adults with non-dialysis CKD stage 3b-4 in one country. Follow-up was 12 months, and the null vascular findings may not generalize to clinical cardiovascular events. The apparent fall-rate difference was based on small event numbers and does not alter the overall null vascular conclusion.