This essential nutrient plays a vital role in the protection of bone and heart health.
Although the liver uses vitamin K1 to make clotting proteins, vitamin K2 is the preferred form used in other parts of the body.
Most of the vitamin K in our diet is in the form of vitamin K1, which is found in plants such as cauliflower, broccoli and dark green leaves.
Only around 10 per cent is in the form of vitamin K2, which is mostly obtained from liver, cheeses, egg yolk, meats and fermented foods such as probiotic yoghurt, cheese and natto.
Some vitamin K2 is also made naturally by probiotic bacteria in the bowel, although the amounts absorbed are not enough to meet our needs – especially in older people.
Some vitamin K2 can be made from vitamin K1 within artery walls and internal organs, but when vitamin K intakes are low, the liver holds on to its reserves so that little is available for conversion elsewhere.
How does it work?
Vitamin K2 is involved in the synthesis and activation of a series of proteins that bind calcium. In the bones, vitamin K2 regulates bone remodelling, while elsewhere it helps to protect against calcification of tissues.
What can it help?
Vitamin K2 activates a protein within the arteries that inhibits calcification of artery walls. This is vital for blood vessel health, as there is no other nutrient-effective way to prevent calcification within the circulation.
By protecting against the hardening of arteries, vitamin K2 may help to protect against high blood pressure and coronary heart disease.
In a study involving over 16,000 women monitored for eight years, every 10mcg increase in dietary vitamin K2 intake was found to reduce the risk of coronary heart disease by nine per cent.
Another study involving 36,600 people found that those with the highest vitamin K2 intake were 29 per cent less likely to develop peripheral arterial disease caused by vascular calcification than those with the lowest intakes.
Vitamin K2 is considered to be vital for the maintenance of normal bones and for protecting against bone thinning.
Calcium-binding proteins found in bones, which depend on vitamin K2, stimulate the formation of new bone by cells known as osteoblasts. Vitamin K2 and vitamin D3 also work together to inhibit the reabsorption of bone by cells known as osteoclasts.
In studies, postmenopausal women with osteoporosis saw significant improvement in bone mineral density of the spine when taking vitamin K2 supplements, compared with placebo.
Vitamin K2 is an approved treatment for osteoporosis in Japan.
The EU RDA for vitamin K is 75mcg. Look for supplements supplying vitamin K in the form of vitamin K2 rather than vitamin K1 to obtain the heart and circulatory benefits.
Seek medical advice before taking supplements containing vitamin K if you are taking warfarin or have a blood clotting disorder.