Vitamin K is synthesized by bacteria in the large intestine. Vitamin K is an essential nutrient that helps the body in blood clotting, bone metabolism, and regulating calcium levels. While vitamin K can be obtained from dietary sources, it is also produced by the bacteria that live in the large intestine. These bacteria produce a form of vitamin K that the body can absorb and use. However, some factors such as antibiotics or gastrointestinal diseases can reduce the amount of vitamin K that is produced by the gut bacteria, leading to vitamin K deficiency.