Vitamin K is a fat-soluble vitamin. The form of vitamin K present in foods is phytomenadione (vitamin K1). The substances synthesised by bacteria in our digestive system are known as menaquinones (vitamin K2). The actual letter ‘K’ stands for the Danish word ‘koagulation’ meaning coagulation or clotting.
Vitamin K is essential for normal blood clotting. It is an essential co-factor for the liver to synthesise proteins involved in the regulation of blood clotting. These are called prothrombin factors.
Vitamin K is involved in the synthesis of a bone protein called osteocalcin, to its active form. Osteocalcin controls the function of calcium in bone turnover and mineralisation. Without vitamin K the bones produce an abnormal protein that is not compatible with other minerals that help form bones.
Why you may need vitamin K
Osteoporosis – evidence suggests that vitamin K deficiency may contribute to osteoporosis. Studies have shown that patients taking anticoagulants, which are vitamin K antagonists are at increased risk of osteoporosis.
How much do you need?
Adequate Intake levels are:
Adults (over 19 years): 60mcg (women), 70mcg (men) daily
Pregnancy: 60mcg daily
Breastfeeding: 60mcg daily
Children 9-13 years: 45mcg daily
Children 14-18 years: 55mcg daily
Symptoms of deficiency
Haemorrhaging (bleeding) disease is a vitamin K deficiency disease characterised by excessive bleeding. Vitamin K can help regulate clotting. Vitamin K can also reduce excessive bleeding induced by certain medications eg salicylates and warfarin.
Deficiency symptoms may include bone abnormalities, hip fracture, easy bruising, haemorrhaging, gastrointestinal bleeding, increased clotting time and nose bleeds.
The best dietary sources of vitamin K include leafy green vegetables, broccoli, Brussel sprouts, kale, soybean oil, kelp, meat, liver milk and eggs.
Other reasons why you may need more
Vitamin K is widely available in foods therefore the most common reason that you may need more is due a malabsorption problem such as coeliac disease, Crohn’s disease or ulcerative colitis. In addition, since vitamin K is metabolised in the liver and vitamin K1 (phylloquinone) is concentrated and retained in the liver, excessive intakes of alcohol or liver disease can increase your vitamin K requirements.
Vitamin K deficiency can also occur in newborn babies and in fact all newborns are actually administered vitamin K. When a baby is born their digestive tract is sterile and the bacteria that produces vitamin K has not been established in the intestines.
If you are taking certain medications, some can increase the need for vitamin K eg overdosing with anticoagulants such as warfarin, anticonvulsant drugs, mineral oils such as paraffin, high intake of antibiotics which kill of all bacteria including those necessary to synthesise vitamin K. Intestinal infections can also affect the bacteria in the intestines. Extensive surgery can interfere with your body’s ability to clot normally.
- Vitamin E reduces the absorption of vitamin K. Large doses of vitamin E greater than 800 IU
daily can increase the risk of bleeding in people who are taking warfarin, other anticoagulants or have low vitamin K intakes.
- Excessive intake of vitamin A (hypervitaminosis) can lead to a deficiency in clotting factor ‘thrombin’ in the blood causing increased bleeding time. Vitamin K can correct the problem.