Vitamins: Vitamin K

Question 1

Vitamin K

Answer 1

Named after K for koagulation (German spelling); discovered during investigation of bleeding disorders in animals.
Three types of compounds have vitamin K activity: K1, K2, K3:
 K1 (phylloquinone): the dietary source found it green leafy vegetables – natural form, making up about 80 to 90% of daily intake. K1 must be converted to K2 in the body to be utilised
 K2 (menaquinones): synthesized by bacteria, found in fermented foods, making up about 10%. Probiotics can support intestinal K2 production. K2 synthesis by bacteria occurs in the human jejunum and ileum, and is absorbed to a limited extent
 K3 (menadione): a potentially toxic, synthetic form used in livestock
Quinone = refers to chemical structure

Question 2

Food sources

Answer 2

 Natto
 Dark green leafy vegetables
 Best absorbed with some dietary fat, e.g. steamed broccoli and kale with some extra-virgin olive oil

Question 3

Dosage

Answer 3

 Optimal intake is 300-500 mcg /day. (Few countries set a daily requirement)

Question 4

Storage and absorption

Answer 4

 K2 is better absorbed and tends to stay within the body for longer
 Only small amounts are stored (mainly in the liver) and a regular directory supply is required.
 Approximately 30 to 40% of ingested vitamin K is retained – the rest is excreted
 Reduced absorption:
o High vitamin A intake
o Aspirin.
o Low bile secretion and poor fat absorption disease states

Question 5

Blood clotting: function and therapeutic uses

Answer 5

 Function:
o Vitamin K is required for the formation of 4 out of the 13 clotting factors (II, VII, IX, X)

 Therapeutic uses:
o Prevent bleeding (it is an antidote to warfarin). Vitamin K is recycled via the vitamin K cycle – warfarin inhibits this

Question 6

Bone Mineralisation: function and therapeutic uses

Answer 6

 Function:
o Osteocalcin (a calcium binding protein in bones) requires vitamin K for synthesis.
o Osteocalcin synthesis by osteoblasts is regulated by active vitamin D (calcitriol)
 Therapeutic uses:
o Osteoporosis (45 mg/day, and by supporting microflora)
o Prevent calcium accumulation in arteries and kidneys

Question 7

Causes of deficiency

Answer 7

 Liver diseases
 Warfarin
 Antibiotic use
 Fat Malabsorption issues

Question 8

Causes of deficiency: Maternal considerations

Answer 8

 Vitamin K transfer to the foetus via the placenta is not significant (although it is generally adequate). Maternal medication such as antibiotics, anticonvulsants and warfarin can dramatically reduce stores
 A vitamin K injection is offered at birth to newborns to prevent potential haemorrhagic disease

Question 9

Deficiency signs and symptoms

Answer 9

 Excessive bleeding (Haemorrhages)
 Bruising
 Bone fractures
 Soft tissue calcification

Question 10

Toxicity

Answer 10

 K1 and K2 are not known to be toxic
 K3 can be toxic

Question 11

Vitamin K injection for newborns

Answer 11

 Considerations of the vitamin K injection:
o Undesirable preservatives (E.g. polysorbate 80; Aluminium in the US)
o Has not been tested for adverse effects such as mutagenicity
o It is a synthetic chemical (despite the name ‘vitamin’)
o The risk in full-time babies is 1:100,000
o A larger dose is given than a newborn requires
 What’s the alternative?
o Delayed cord clamping until the placenta has fully pulsed out
o Increased intake of vitamin K-rich foods (e.g. leafy greens) before due date, and to support mothers microflora (K2)
o Nettle leaf infusions are a great source of vitamin K2
o Vitamin K amounts in the newborn’s blood increase daily

http://www.youtube.com/watch?v=Cw53X98EvLQ

Question 12

Vitamin K functions:

Answer 12

Blood clotting
Bone mineralisation