Vitamin K is needed for proper bone formation and blood clotting. In both cases, vitamin K does this by helping the body transport calcium. Vitamin K is used by doctors when treating an overdose of the drug warfare. Vitamin K also helps to prevent and fight osteoporosis, a disease that affects more than 25 million Americans. Adults ages 18 to 44 who take in about 1 mg per 2.2 pounds of their body weight per day of vitamin K have proper bone formation and consequently decreasing their chances of Osteoporosis. In a study including 148 people testing bone mineral density was examined and they had a vitamin K intake, those with lower bone density had a mean vitamin K intake of 161 mg per day; those with higher bone density took 217 mg per day. Vitamin K is a fat-soluble vitamin essential for the production of prothrombin and several other proteins involved in the blood clotting system, and the bone protein osteocalcin. Deficiency causes impaired blood coagulation and haemorrhage. Two groups of compounds have vitamin K activity: phylloquinones, found in all green plants, and a variety menaquinones synthesized by intestinal bacteria.