Supplements

Vitamin K (Menadione)

Vitamin K (menadione) is a fat-soluble vitamin usually measured in micrograms (mcg). Vitamin K is needed for the production of prothrombin, which is necessary for blood clotting. Vitamin K is manufactured through intestinal bacteria.

There are three forms of vitamin K: vitamin K1 (Phylloquinone or phytonactone), which comes from plants; vitamin K2, a family of substances called menaquinones, which are made by intestinal bacteria; and vitamin K3 (menadione), which is a synthetic substance.

Vitamin K is essential for the synthesis of osteocalcin, the protein in the bone tissue on which calcium crystallizes. Without vitamin K, the calcium passes directly through the body, usually through urine, and the risk of bone fractures rises correspondingly. Women with osteoporosis have, on average, only 25 percent of the vitamin K found in their otherwise healthy counterparts.

Osteocalcin production resumes, with supplementation of vitamin K, calcium excretion slows, and bone begins to form again.

Vitamin K plays an important role in the intestines and aids in converting glucose into glycogen for storage in the liver, promoting healthy liver function.

Vitamin K helps in the prevention of internal bleeding and hemorrhages; and also aids in reducing excessive menstrual flow.

Studies indicate that it may contribute to cancer prevention, by selectively killing cancer cells. Laboratory experiments show that supplements, in conjunction with vitamin C, can inhibit the growth of cancer cells in the breast and the endometrium.

Deficiency: Celiac disease, sprue, colitis. Chemotherapy can also lead to a deficiency, as can the use of antibiotics and most antiseizure medications.

Depleting Agents: Antibiotics, antiseizure medications, chemotherapy, x-rays, frozen foods, aspirin, air pollution, and mineral oil.

Sources: The majority of the body's supply of vitamin K is synthesized the friendly bacteria normally present in the intestines. Food sources are green leafy vegetables, spinach, dark lettuce, broccoli, Brussels sprouts, cabbage, cauliflower, asparagus, blackstrap molasses, whole wheat, whole oats, fresh peas, egg yolks, liver, oatmeal, safflower oil, soybeans and yogurt.

Herb Sources: Alfalfa, green tea, kelp, nettle, oat straw, and shepherd's purse.

Precautions: Vitamin K can interfere with the action of anticoagulant drugs, consult your physician before taking any supplement with vitamin K. Do not take synthetic Vitamin K (K3 ­ menadinone) during the last few weeks of pregnancy as it can result in a toxic reaction in the newborn.

Dosage Ranges and Duration of Administration: Some researchers suggest that women, in particular, should take a daily 100 mcg supplement (provided, of course, that they are not undergoing anticoagulant therapy). The relationship with bone strength also seems to call for an adjustment in the current RDA for the vitamin, now set at just 65 mcg for women and 80 mcg for men, says Dr. Robert C. Atkins.