Nutritional sources of vitamin K

To review the function of vitamin K in clotting and methods of its analysis, to present results of previous studies on the role of dietary vitamin K in humans and animals, and to reanalyze these data in light of current methods.

A review of assumptions stated in the literature is presented, including the incorrect theory that a diet-induced deficiency of vitamin K is nonexistent and the unsubstantiated hypothesis that antibiotics can cause vitamin K deficiency by destroying intestinal bacteria.

The insistent belief that intestinal bacteria are an important source of vitamin K has led to erroneous conclusions about the sources of vitamin K for human nutrition. In the future, the importance of various sources of vitamin K, their pathways of absorption, and their susceptibility to administration of antibiotics should be evaluated without recourse to current assumptions.