Vitamin K is an umbrella term encompassing a group of chemically related fat-soluble compounds known as naphthoquinones.
This group includes vitamins K, K1, K2, and K3. Vitamin K1 (phytonadione) is the natural form of vitamin K; it is found in plants and is the primary source of vitamin K that humans obtain through foods.
Especially high sources of vitamin K are spinach, Brussels sprouts, green beans, asparagus, Swiss chard, broccoli, kale and mustard greens.
Even though vitamin K has not been shown to be an antioxidant in the same sense as vitamin C and E, the basic forms of vitamin K, including phylloquinones and menaquinones, have been shown to protect cells from oxidative stress.
Vitamin K is an essential part of glumatic acid, an amino acid that causes the chemical event called carboxylation.
This chemical event allows the blood from an open wound to stick to the nearby tissue, thus clotting the open wound and preventing an excess of blood from flowing out.
Nose bleeding, heavy menstrual bleeding, easy bruising, hemorrhaging and anemia are just some of the indications that a person is vitamin K deficient.
Certainly, Vitamin K ensures healthy bones by two means.
First of all, vitamin K blocks the formation of too many osteoclasts, or bone cells, that take minerals from the bones and make them available to other bodily functions (a process called demineralization).
In the end, the formation of osteoclasts, if not properly checked, can leave bones overly depleted of their minerals. 
A protein found in bones, directly related to our bone mineral density, called osteocalcin, must be chemically altered through carboxylation (the process mentioned above in regards to blood clotting) to maintain optimal health.
Hence, Vitamin K is a key ingredient in carboxylation, and with proper intake can allow the protein osteocalcin to strengthen the health and composition of our bones.
Consequently, the build-up of calcium inside the tissue, or calcification, can become a serious problem that may lead to cardiovascular disease.
Vitamin K helps prevent calcification by contributing to the process (mentioned again) called carboxylation.
This process produces the matrix Gla protein (MGP) that directly prevents calcium from forming in tissue.
Without a proper supply of vitamin K, and thus MGP, the body is at greater risk of atherosclerosis, cardiovascular disease, and stroke.
As a result of healthy vitamin K levels, the release of the glycoprotein interleukin-6, a marker of inflammation within the body is shown to be significantly lower.
The myelin sheath, or the outer wrapping around a nerve, needs sphingolipids (a crucial fat) to form properly.
Vitamin K is known to be essential for the synthesis of the sphingolipids, and therefore proper brain and nerve function.
A deficiency in vitamin K can lead to defective blood clotting, increased bleeding and osteoporosis.
Symptoms may include bruising easily, excessive menstrual bleeding, gastrointestinal bleeding, and possible blood in the urine.
People with chronic malnutrition, those with alcohol dependency, and anyone with health conditions that limit absorption of dietary vitamins is most at risk for a vitamin K deficiency.
Adults and children who eat a balanced diet that include spinach, brussels sprouts, green beans, asparagus, swiss chard, broccoli, kale and mustard greens, will obtain enough vitamin K and do not need supplementation.
People who may benefit from supplemental vitamin K are babies (who usually get a shot of vitamin K at birth) and those with digestive diseases.
Resources: DrWeil.com, livestrong.com, medicalnewstoday.com
