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Vitamin K (Phylloquinone, Menaqionone, Menadione)

Vitamin K Functions

Vitamin K is a fat-soluble vitamin, an essential nutrient required for [1]:

  • Normal function of blood clotting factors and thus for blood clotting
  • Normal bone strength

Vitamin K exists in the following forms:

  • Vitamin K1 or phylloquinone, phytomenadione or phytonadione is found in plant foods; it is also used as a supplement for injection in infants.
  • Vitamin K2 or menaquinone is synthesized by normal intestinal bacteria.
  • Vitamin K3 or menadione is a synthesized form used for vitamin K injections in adults.

Vitamins K has got its name from the German word koagulation = blood clotting [1].

Recommended Daily Intake

The Adequate Intake (AI) for vitamin K for adult men is 120 mcg/day, and for women (including during pregnancy and breastfeeding) 90 mcg/day [1].

Foods Rich in Vitamin K

  • PLANT FOODS (vitamin K1): green leafy vegetables, nuts (pine nuts, cashews), fruits, vegetable oils, margarines
  • ANIMAL FOODS: tuna (light), abalone; other animal foods contain only small amounts of vitamin K
  • Human breast milk contains about 3 mcg vitamin K1/liter, which is enough to meet the needs of infants 0-12 months old
  • References: [1,3]

Normal large intestinal bacteria can produce some vitamin K2 (menaquinone), but it is not clear if this is enough to meet the body needs [1].

Vitamin K Deficiency: Causes, Symptoms

Vitamin K deficiency, especially in adults, is rare; it can occur in [4]:

  • Exclusively breastfed infants or infants whose mothers take anticonvulsants
  • Low vitamin K intake in chronic alcoholism or malnutrition
  • Fat malabsorption (and thus vitamin K malabsorption) due to a chronic liver or bile duct disease, chronic pancreatitis, cystic fibrosis, celiac disease, Crohn’s disease, ulcerative colitis, tropical sprue, intestinal parasites, small intestinal bacterial overgrowth (SIBO), short bowel syndrome (SBS) after extensive bowel resection
  • Gastric bypass (bariatric surgery for weight loss) [5]
  • Cholestyramine, warfarin (anticoagulant drug or rat poison), cefamandole, cefoperazone, salicylates, rifampin, isoniazid, barbiturates, mineral oils, high doses of vitamin A or E, orlistat, olestra may reduce vitamin K absorption or activity.
  • Multiple myeloma, massive transfusion and disorders that affect blood, such as disseminated intravascular coagulation (DIC), polycythemia vera, nephrotic syndrome and leukemia.

Symptoms. Vitamin K deficiency leads to impaired blood clotting resulting in heavy menstrual bleeding, nosebleeds, gum bleeding, blood in the urine or stool, excessive bruising.

Diagnosis of vitamin K deficiency is confirmed by an elevated prothrombine time (PT) that becomes normal within few hours after vitamin K injection [1]. Certain liver disorders may affect synthesis of vitamin K dependent coagulation factors, resulting in the same type of bleeding as in vitamin K deficiency. Treatment is with vitamin K supplements.

Vitamin K Deficiency Bleeding (VKDB) Disorder of the Newborn

In infants, vitamin K deficiency may occur since vitamin K from the mother to the fetus passes poorly through the placenta, and newborns have no vitamin K stores and no intestinal flora that could produce it. Newborns at increased risk of vitamin  deficiency are those whose mothers had vitamin K deficiency during pregnancy due to malnutrition or taking drugs, such as carbamazepine, phenytoin, barbiturates, cephalosporins, rifampin, or isoniazid [6,7].

Symptoms of VKDB include bleeding from the umbilicus, gastrointestinal tract, nose or mouth. Rarely, a life-threatening bleeding within the skull can occur. Bleeding usually occurs in the first week after birth [6].

In many countries, all newborns get an intramuscular injection of vitamin K1 shortly after birth to prevent vitamin K deficiency bleeding (VKDB) disorder of the newborn.

Exclusively breastfed infants who did not get vitamin K injection at birth are also at increased risk to develop vitamin K deficiency and bleeding up to six months after birth [6].

Vitamin K Supplements

Without prescription:

  • Certain multivitamins contain small amounts of vitamin K1 or K2.

By prescription:

  • Vitamin K1 (phylloquinone) as a tablet or injection (under the skin, into the muscle or vein)
  • Vitamin K2 (phytomenadione)

Possible Vitamin K Supplements Benefits

There is CONVINCING EVIDENCE that vitamin K is effective in [8]:

  • Prevention and treatment of vitamin K deficiency
  • Reversing effects of warfarin overdose

There is INSUFFICIENT EVIDENCE about vitamin K effectiveness in prevention or treatment of atherosclerosis, bruises, burns, heart disease, high cholesterol, osteoporosis, scars, spider veins, stretch marks or swelling [1,8].

Vitamin K Supplements Safety: Side Effects, Toxicity

No Tolerable Upper Intake level (UL) has been established for vitamin K [1].

Possible side effects: decreased appetite, irritability, yellow eyes or skin, paleness, enlarged liver, muscle stiffness, difficulty breathing, altered taste, flushing [2,9]. Rarely, after vitamin K injection, drop of blood pressure, fast breathing, fainting, skin rash, facial swelling, drop of blood pressure may occur, and after intravenous injection, a life threatening anaphylactic reaction may develop [2,9]. Newborns may have jaundice if there mothers are taking high doses of vitamin K supplements during pregnancy [2].

Toxicity from vitamin K supplements has not been observed [1].

During Pregnancy

Pregnant women who intend to take vitamin K supplements should speak with their doctors. Vitamin K is category C drug, which means no harmful effects in fetuses have been observed, but they can not be excluded because insufficient studies have been done [2]. Vitamin K supplements are safe to use during breastfeeding.

The use of warfarin, anticonvulsants, rifampin, and isoniazid during pregnancy can result in the increased risk of vitamin K deficiency in the newborn.

Vitamin K Interactions With Drugs and Nutrients

  • Nutrients and drugs that may lower vitamin K absorption: cholestyramine, cholestipol, orlistat, mineral oil, olestra, long-term treatment with antibiotics or salicylates, and high doses of vitamin A.
  • High doses of vitamin E (800 IE or higher) reduce clotting effect of vitamin K [2,8].
  • High doses of vitamin K, especially if used along with coenzyme Q10, may lower the effect of an anticoagulant medication warfarin and thus increase the risk of blood clots [8].

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