ARTICLE - VITAMIN K

SUMMARY

THE ARTICLE

Other Names:

Phylloquinone, Menaquinone

Classification:

Vitamin

Properties of Vitamin K:

• Vitamin K is a general term for a family of compounds with similar actions in the body. These compounds include Phylloquinone (or vitamin K1) and Menaquinone (or vitamin K2). Phylloquinone is converted to the active form Menaquinone by the liver.
• Both forms of vitamin K are fat soluble.
• Vitamin K is stable to heat and reduction.
• Vitamin K is unstable to light, oxidation, acid and alkali.

Functions of Vitamin K:

• Production of blood clotting factors
• Production of the bone proteins Osteoclacin and MGP, which stimulate bone remodelling, calcium mobilisation and inhibit growth plate mineralisation.
• Production of Gla protein in the kidneys which prevents kidney stone formation.
• Involved with vitamin D in the formation of calcium binding proteins in the intestines.
• A co-factor in the synthesis of lung surfactant apoprotein
• Involved with the differentiation of leukemic cells and induces cell apoptosis
• Improves brain tissue repair

Absorption:

Vitamin K is absorbed in the small intestines, specifically in the jejunum and ileum. Absorption is dependent on the presence of bile and pancreatic juices and may be inhibited by lack of dietary fat.

Storage:

The body stores very little vitamin K and the turnover is rapid. Any vitamin K stored is found in the liver, with smaller amounts in the adrenal glands, lungs, bone marrow and lymph nodes. The body does however, have a process that can conserve vitamin K stores, by reactivating used vitamin K in order to reuse it.

Excretion:

60-70% of Vitamin K is metabolised by the liver and excreted in urine and bile within a few days.

RDI (Recommended Dietary Intake) of Vitamin K:

There is currently insufficient data to formulate a RDI for vitamin K.  Therefore the following figures refer to the AI (Adequate Intake) which is the daily nutrient intake level based on the average vitamin K intakes of groups of healthy people.

Dietary Sources of Vitamin K:

• Alfalfa
• Asparagus
• Broccoli
• Cabbage
• Camembert cheese
• Eggs
• Green Tea
• Kale
• Kelp
• Lettuce
• Liver  
• Oats
• Pork
• Soybeans
• Spinach
• Turnip greens

Note: About 50% of vitamin K needs may be supplied by gut flora.

Risk of Deficiency of Vitamin K:

People with the following conditions or circumstances are at greater risk of deficiency:

• Anticoagulant drug therapy including warfarin and aspirin
• Apo-4 phenotypes      
• Calcium supplementation
• Coeliac disease
• Crohn’s disease
• Diarrhoea and intestinal infection
• Fat malabsorption or very low fat diets
• Gall or Liver disease or surgery
• Long term parental nutrition
• Long term use of antibiotics and sulphur drugs
• Newborn infants, especially when breastfed
• Post menopausal women
• Rheumatoid arthritis
• Ulcerative colitis
• Vitamin A and E excess

Therapeutic Uses of Vitamin K:

 This nutrient may play a role in the prevention and/or treatment of the following conditions:

• Acute leukaemia
• Ageing
• Alzheimer’s disease
• Arteriosclerosis
• Astrocytomas
• Biliary obstruction
• Bleeding gums
• Bruising
• Calcium kidney stones
• Cerebral haemorrhage
• Child birth
• Coeliac disease
• Colitis
• Crohn’s disease
• Cystic fibrosis
• Epistaxis
• Fractures
• Gliomas
• Haemorrhage
• Haemorrhage in the eye
• Low bone density/Osteoporosis
• Paget’s disease
• Pain
• Pancreatic insufficiency
• Periodontal disease
• Poor mitochondrial function
• Post operative haemorrhage
• Rheumatoid arthritis
• Surgery
• Vitamin D toxicity

Therapeutic Dose of Vitamin K:

The safe therapeutic dosage range for the above disease states is 2-20mg. Therapeutic treatment with vitamin K should only be undertaken under supervision by your doctor, dietician, nutritionist, naturopath or other trained medical professional.  It is also important to note that herbal and nutritional supplements may interact with pharmaceuticals and other medical treatments and it is therefore necessary to always inform your practitioner of everything you are currently taking.

Contraindications and Cautions of Vitamin K:

High doses of Vitamin K impair the anticoagulating properties of medications such as warfarin and aspirin, which are used to prevent blood clotting.  Those on these medications should not use vitamin K supplements and should ensure dietary intakes are minimal and stable.

References:

Australian Government, Department of Health and Ageing, National Health and Medical Research Council, 2006, Nutrient Reference Values for Australia and New Zealand Including Recommended Dietary Intakes, Commonwealth of Australia, ACT, Australia. 

Braun, L. and Cohen, M., 2007, Herbs and Natural Supplements an Evidence-based Guide, 2nd Ed, Elsevier, NSW, Australia.

Osiecki, H.,2008, The nutrient Bible, 7th Ed, Brumby Books, VIC,  Australia.

Rolffs, SR., Pinna, K., Whitney, E., 2009, Understanding Normal and Clinical Nutrition, 8th ED, Wadsworth Cengage Learning, CA, USA.

Sharon, M., 2009, Nutrients A-Z, 5th Ed, Carlton Books Ltd, London, UK.

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