Circulating phylloquinone concentrations of adults in the United States differ according to race and ethnicity.
Shea MK, Booth SL, Nettleton JA, Burke GL, Chen H, Kritchevsky SB. Circulating phylloquinone concentrations of adults in the United States differ according to race and ethnicity. J Nutr. 2012 Jun; 142(6):1060-6.