Vitamin D supplementation has been widely promoted to restore 25-hydroxyvitamin D concentrations; however, experimental evidence suggests a nutrient interaction with vitamin K. We assessed the effects of 1200 IU vitamin D₃ per day versus placebo for six months on vitamin K status in a randomized, double-blind, placebo-controlled trial with participants aged 60⁻80 years with depressive symptoms and ≥1 functional limitation for a secondary analysis. Stored baseline and six-month follow-up blood samples were available for 131 participants (n = 65 placebo vs. n = 66 vitamin D supplementation). We measured dephosphorylated uncarboxylated matrix gla protein (MGP) (dp-ucMGP) concentrations-a marker of vitamin K deficiency. Mean age was 68 years, and 89 participants (68%) were women. Vitamin K antagonists were used by 16 participants and multivitamin supplements by 50 participants. No differences in change between intervention and placebo were found (-38.5 ± 389 vs. 4.5 ± 127 (pmol/L), p = 0.562). When excluding vitamin K antagonist users and multivitamin users, dp-ucMGP at follow-up was significantly higher in the vitamin D group (n = 40) compared to placebo (n = 30), with a difference of 92.8 (5.7, 180) pmol/L, adjusting for baseline dp-ucMGP and sex. In conclusion, vitamin D supplementation for six months did not affect vitamin K status; however, among participants without vitamin K antagonist or multivitamin use, vitamin D supplementation influenced dp-ucMGP concentrations.
van Ballegooijen, A. J., Beulens, J. W. J., Schurgers, L. J., de Koning, E. J., Lips, P., van Schoor, N. M., & Vervloet, M. G. (2019). Effect of 6-Month Vitamin D Supplementation on Plasma Matrix Gla Protein in Older Adults. Nutrients, 11(2), . https://doi.org/10.3390/nu11020231, https://doi.org/10.3390/nu11020231