Comparative aspects of human vitamin K metabolism and nutriture.

phylloquinone (vitamin K1) versus menaquinones (vitamins K2), and their relative contribution in meeting the needs for vitamin K, not only for the synthesis of the hepatic coagulation factors but also for the less well understood vitamin K-dependent carboxylation reactions in other tissues such as bone. Largely unanswered questions surround the comparative intermediary metabolism and transport of phylloquinone and menaquinones and their comparative intracellular distribution and in vivo activity. Perhaps the most perplexing question is the nutritional origin of tissue menaquinones (MKs) and more specifically:-does the enormous microfloral population of the large intestine provide an important nutritional source of vitamin K or are MKs largely of dietary origin? Another area of possible comparision is health versus disease. For example an important question is how various disease states may influence the metabolism and hence the needs for vitamin K or our perception of these needs. Some results pertaining to the above questions are addressed below.