Vitamin K

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.

 

VITAMIN K: OVERDOSE/TOXICITY

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.

 

VITAMIN K: ADVERSE REACTIONS OR SIDE EFFECTS

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.

 

VITAMIN K: INTERACTION WITH OTHER SUBSTANCES

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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