COLLOIDAL MINERALS

Vitamin K functions in metabolism as a substrate for a microsomal enzyme that catalyzes the post translational conversion of specific glutamyl residues in a limited number of proteins to g-carboxyglutamyl (Gla) residues. The proteins involved include clotting factors II (prothrombin), VII, IX, and X, plasma proteins C and S, osteocalcin, and matrix Gla protein. Phylloquinone (2-Me-3-phytyl-1,4-naphthoquinone) from plants and a series of bacterial menaquinones (2-Me-3-polyisoprenyl-1, 4-naphthoquinone) are natural forms.

Deficiencies:
The classical symptom of a vitamin K deficiency is a defect in blood coagulation measured by a one-stage prothrombin time (clinical PT). Uncomplicated deficiencies are rare. The hemorrhagic disease of the newborn is a potential risk, particularly for breast-fed infants, but is preventable by vitamin K prophylaxis at birth.

Diet recommendations:
The current Recommended Dietary Allowances (RDAs) for vitamin K are:

Past estimates of vitamin K intake were in the range of a few hundred µg/day; current data suggest that a range of intake of 75-125 mg of phylloquinone/day is more accurate. The contribution of menaquinones in the lower bowel to satisfying the human requirement is unknown, but it is probably minor.

Food Sources:
Excellent sources of phylloquinone in the diet are dark green vegetables such as spinach, broccoli, and kale. These foods may provide more than one RDA in a single serving. Other green vegetables also furnish significant amounts. Bioavailability of vitamin K from various food sources has not been established. Meats, grains, and fruits contribute little vitamin K to the diet, but soybean oil, canola oil, and olive oil furnish appreciable amounts.

Toxicity:
Large amounts of phylloquinone can be consumed over extended periods with no toxic effects. Menadione (2-Me-1,4-naphthoquinone) is currently used in animal feeds but is not longer administered to infants because of resulting hemolytic anemia, hyperbilirubenemia, and kernicterus.

Recent Research:
A number of reports point to a relationship between vitamin K status and skeletal health of the elderly. If these findings turn out to be correct, they will open an exciting new area of research in the field of vitamin K metabolism.

For Further Information:

Suttie, J.W. (1992) Vitamin K and human nutrition. J. Am. Diet. Assoc. 92: 585-590

Suttie, J.W. (1993) Synthesis of vitamin K-dependent proteins. FASEB J. 7: 445-452

Booth, S.L., Pennington, J.A.T. & Sadowski, J.A. (1996) Food sources and dietary intakes of vitamin K-1 (phylloquinone) in the American diet: J. Am. Diet. Assoc. 96: 149-154.

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