Vitamins K (vitamins K1and K2) are micronutrients with wide range of biological functions. Vitamin K1 (phylloquinone) is of plant origin and principally controls some blood clotting factors synthesized by the liver. Many forms of vitamin K2 (menaquinones) have various biological potencies and functions. This depends on the length of the side-chain. It is synthesized by microbiota of the large intestine besides being synthesized in tissues from phylloquinone by a specific enzyme in the liver and other tissues. Vitamin K2 is essential for preventing vascular microcalcification which affects both small and large arteries and contributes for pathological complications of renal and diabetic diseases. It has anti-osteoporotic action and maintains bone density. Its anti-inflammatory and anti-oxidant activities protect against many pathological states. It may account for improving glucose tolerance owing to its insulinotropic effect, and counter-against cancer due to both anti-apoptotic and anti-oxidant actions. It has biolological actions on the nervous system including peripheral nerves and protects against Alzheimer's disease.