Vitamin K (Phylloquinone or Menaquinone)
Keywords: blood clotting, bone health
- Production of four proteins involved in blood clotting
- Involved in bone calcification and mineralization
Good food sources
- Brussels sprouts
- Cabbage and other leafy green vegetables
- Green tea
- Soybean, rapeseed and olive oils
- Whole grains
Deficiency signs and symptoms
- Bleeding and haemorrhage
- Increased urinary calcium excretion
Vitamin K can be synthesized by Bacteroides bacteria in the small intestine so it is not essential to obtain all vitamin K from the diet unless these bacteria have been depleted by taking antibiotics. Bacterial synthesis alone is not sufficient to meet all the body’s needs. Vitamin K produced by bacteria in the colon is not absorbed.
Since vitamin K is fat-soluble, the presence of chronic diarrhoea, or any defect in fat digestion and absorption, or a deficiency of fat or oil in the diet, could result in depletion of vitamin K levels. About 60-70 per cent of dietary vitamin K is excreted daily, so a daily intake of vitamin K-rich foods is advisable. The long-term use of aspirin-based painkillers increases vitamin K requirements.
The plant form of vitamin K is known as phylloquinone. Intestinal bacteria synthesize a family of compounds with vitamin K activity known as menaquinones. Liver stores of vitamin K are small, and mainly consist of menaquinones. Bone contains substantial concentrations of both phylloquinone and menaquinones.
Vitamin K is often given routinely to newborn, especially premature, babies to prevent haemorrhagic disease of the newborn. Newborn infants have a low vitamin K level due to the lack of gut bacteria in the first few days of life.
Proteins found in bone tissue—known as osteocalcin, bone Gla protein and matrix Gla protein—are dependent on adequate vitamin K levels. Vitamin K is also needed to enable calcium to bind to the protein matrix of bone, and helps to prevent calcium losses in urine.
Information compiled by Linda Lazarides
Naturopathic Nutritionist, Author, Educator