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 compound have vitamin K activity: K1, K2, K3.

Question 2

Vitamin K: K1

Answer 2

• K1 (Phylloquinone): the dietary source found in green leafy vegetables natural form, making up about 80-90% of daily intake. K1 must be converted to K2 in the body to be utilised.

Question 3

Vitamin K: K2

Answer 3

• K2 (Menaquinones): synthesised by bacteria, found in fermented foods , making up around 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.

Question 4

Vitamin K: K3

Answer 4

• K3 (Menadione): a potentially toxic, synthetic form used in livestock.

Question 5

Vitamin K: Food Sources

Answer 5

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

Question 6

Vitamin K: Dosage and Absoprtion

Answer 6

• Optimal intake is 300-500mcg/day. Few countries set a daily req.
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 dietary supply is required. Approximately 30-40% of ingested vitamin K is retained the rest is excreted.
• Reduced absorption: High vitamin A intake, aspirin. Low bile secretion and poor fat absorption disease states.

Question 7

Vitamin K: Roles

Answer 7

Blood Clotting

Bone Mineralisation

Question 8

Vitamin K: Blood Clotting - Functions

Answer 8

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

Question 9

Vitamin K: Blood Clotting - Therapeutic Use

Answer 9

• Prevents bleeding (it is an antidote to warfarin).

Vitamin K is recycled via the Vitamin K Cycle warfarin inhibits this.

Question 10

Vitamin K: Bone Mineralisation - Functions

Answer 10

• Osteocalcin (a calcium binding protein in bones) requires vitamin K for synthesis.
• Osteocalcin synthesis by osteoblasts is regulated by active vitamin D (calcitriol)

Question 11

Vitamin K: Bone Mineralisation - Therapeutic Uses

Answer 11

• Osteoporosis (45mg/day, and by supporting microflora)

* Prevents calcium accumulation in arteries and kidneys

Question 12

Vitamin K Deficiency Causes

Answer 12

Causes of Deficiency:

• Liver diseases, warfarin, antibiotic use, fat malabsorption issues.

Question 13

Vitamin K Deficiency: Signs and Symptoms

Answer 13

• Excessive bleeding (haemorrhages), bruising, bone fractures, soft tissue calcification.

Question 14

Vitamin K: Maternal Considerations

Answer 14

• Maternal considerations: vitamin K transfer to the foetus via the placenta is not significant (although it is generally adequate). Maternal medications 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 15

Vitamin K Injection for Newborns

Answer 15

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

Question 16

Vitamin K: Toxicity

Answer 16

K1 & K2 are not known to be toxic (K3 can be).