Vitamin K plays a vital role in blood clotting. The vitamin contributes to the liverŐs synthesis of prothrombin, which converts to thrombin in the initial steps of blood coagulation. Vitamin K is somewhat unique because it has both fat- or water-soluble forms. One form, K-1 or phylloquinone, is found in many plants and animals, and K-2, or menaquinone, is manufactured by microorganisms, such as bacteria, in the intestinal tract of many animals. K-3 (menadione) is a synthetic version with the basic structure of the naturally occurring vitamins and is twice as active biologically. This version is soluble in boiling water.
In either fat- or water-soluble forms, Vitamin K is effective in raising prothrombin levels and controlling hemorrhage in newborns. Newborns do not have the bacteria form of the vitamin and are often given injections of Vitamin K to prevent hemorrhaging. An alternative to injections is oral supplements taken by the mother during the last few days of pregnancy and administered to the child orally after birth.
Vitamin K deficiencies are uncommon but when they do occur, it is usually the result of anti-coagulant medication or the long term use of antibiotics. These medications interfere with the function of the vitamin. Other Vitamin K inhibitors include aspirin, Dilantin, and high doses of Vitamin E. Because Vitamin K is necessary for healthy bones, deficiency poses an increased risk for severe bone fractures.
Vitamin K-1 is the preferred form, as it converts inactive bone protein into a usable form. It is found in green plants and is often used in conjunction with fat-soluble chlorophyll supplements as a treatment for osteoporosis, menorrhagia (excessive menstrual bleeding), and hemorrhagic disease in infants.
Vitamin K is now believed necessary for the formation and maintenance of healthy bones. Researchers in 1994 speculated that two of the Vitamin K-dependent proteins, which were discovered in bone tissue, regulate calcium metabolism, the mineralization of tissue, and bone turnover.1 Animal studies have shown that anti-coagulation therapy might inhibit the formation of bone proteins similar to the effect the therapy has on blood coagulation proteins.
Until recently, it was assumed that intestinal bacterial synthesis of the vitamin met the daily needs of most individuals. But because a large segment of the American population has a low intake of dark green leafy vegetables, researchers at US Department of Agriculture Human Nutrition Research Center on Aging at Tufts University report there now is the possibility of marginal deficiencies.
1 Dowd P, Hershline R, Ham S, et al., Mechanism of action of vitamin K. Nat Prod R 1994;11:251-264.
VITAMIN K: SOURCES
Available as:
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: PROVEN BENEFITS
What this vitamin does:
Promotes production of active prothrombin (factor II), proconvertin (factor VII) and other clotting factors. These are all necessary for normal blood clotting.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITMAIN K: UNPROVED SPECULATED BENEFITS
None.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: SPECIAL CONSIDERATIONS
Miscellaneous information:
Very little Vitamin K is lost from processing or cooking foods.
When a severe bleeding disorder exists due to a Vitamin K deficiency, fresh whole blood may be needed during severe bleeding episodes. There is a significant delay before Vitamin K becomes effective when given by injection.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: DEFICIENCY SYMPTOMS
Infants:
Adults:
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: UNPROVED SPECULATED SYMPTOMS
Excessive diarrhea.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: LAB TESTS TO DETECT DEFICIENCY
1 From Griffith HW, Vitamins, Minerals, and Supplements.
VITAMIN K: OPTIMAL LEVELS
50-500 mcg.
VITAMIN K: MINIMUM DOSAGE
Recommended Dietary Allowance (RDA):
No RDA has been established. Adequate and safe range is 2 mcg/kg body weight per day. Estimated Safe Intake/Day is given below.
Age Estimated Safe Intake
0-6 months 5mcg
6-12 months 10mcg
1-3 years 15mcg
4-6 years 20mcg
7-10 years 30mcg
Males
11-14 years 45mcg
15-18 years 65mcg
19-24 years 70mcg
25+ years 80mcg
Females
11-14 years 45mcg
15-18 years 55mcg
19-24 years 60mcg
25+ years 65mcg
Pregnant 65mcg
Lactating 65mcg
VITAMIN K: WARNINGS AND PRECAUTIONS
Don't take if you:
Consult your doctor if you have:
Over age 55:
Pregnancy:
Breast-feeding:
Effect on lab tests:
Storage:
Others:
Avoid overdosage. Vitamin K is a fat-soluble vitamin. Excess intake can lead to impaired liver function.
Tell any dentist or doctor who plans surgery that you take Vitamin K.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
Signs and symptoms:
In infants:
In all:
What to do:
For symptoms of overdosage: Discontinue vitamin, and consult doctor. Also see ADVERSE REACTIONS OR SIDE EFFECTS.
For accidental overdosage (such as child taking entire bottle): Call your local poison control center.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
Reaction or effect What to do
Hemolytic anemia in infants Seek emergency treatment.
Hyperbilirubinemia (too much Seek emergency treatment.
bilirubin in the blood) in newborns
or infants given too much Vitamin K
Jaundice (yellow skin and eyes) Seek emergency treatment.
resulting from hyperbilirubinemia
ALLERGIC REACTIONS, INCLUDING:
Face flushing Discontinue. Call doctor immediately.
Gastrointestinal upset Discontinue. Call doctor immediately.
Rash Discontinue. Call doctor immediately.
Redness, pain or swelling at injection site Discontinue. Call doctor immediately.
Skin itching Seek emergency treatment.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
Anti-coagulants (oral) decreases anti-coagulant effect.
Antibiotics, broad spectrum causes Vitamin K deficiency.
Cholestyramine decreases Vitamin K effect.
Colestipol decreases Vitamin K effect.
Coumarin (isolated from sweet clover) decreases Vitamin K effect.
Mineral oil (long term) causes Vitamin K deficiency.
Primaquine increases potential for toxic side effects.
Quinidine causes Vitamin K deficiency.
Salicylates increases need for Vitamin K when administered over long time.
Sucralfate decreases Vitamin K effect.
Sulfa drugs causes Vitamin K deficiency.1
1 From Griffith HW, Vitamins, Minerals, and Supplements.
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