Vitamin K and vitamins D, E, and A are fat-soluble vitamins that can be synthesized by bacteria in the intestine.
These vitamins are essential for various processes in the body, including blood clotting, bone health, vision, immunity, and reproductive health. The body is incapable of producing these vitamins, and they must be obtained from external sources. However, certain bacteria living in the human gut can produce these vitamins and make them available for absorption into the body.