Abstract
There are two naturally occurring forms of vitamin K, vitamin K_1 (phylloquinone) and vitamin K_2 (menaquinones). It has been found that phylloquinone and menaquinones are converted to menaquinone-4 (active form of vitamin K) and can subsequently act exerts their physiological function in the tissue. Clinical studies have shown the relations between vitamin K status and diseases such as osteoporosis, knee osteoarthritis, Alzheimer's disease, artherosclerosis, and cancer. Vitamin K deficiency increases the risk of fractures in the elderly women. Vitamin K_1 reduces the risk of fractures in postmenopausal Western women, while vitamin K_2 (menaquinone-4) is used as an anti-fracture medicine in Japanese patients with osteoporosis. Inadequate intake of vitamin K is found at the advanced stages of knee osteoarthritis and at the early stage of Alzheimer's disease. Vitamin K_2 intake reduces the risk of coronary heart disease in Western people and the incidence hepatocellular carcinoma in Japanese patients with viral cirrhosis of the liver. Vitamin K is suggested to play an important role as an anti-aging medicine. Currently, vitamin K_2 is used in the treatments of osteoporosis, cirrhosis, and hepatocellular carcinoma in the clinical practice.
