Mention vitamins A to E, and most people will know why they need them and what foods contain them. Not so vitamin K, a comparatively little-known vitamin that has been the subject of several recent scientific investigations for its role in bone health and the prevention of blood clots.
A meta-analysis of studies regarding vitamin K and bone health has found that supplementation is associated with increased bone mineral density (BMD) and reduced fracture incidence.
The reduction in fracture incidence is particularly promising, as there was an incredible 80 per cent reduction in hip fractures following supplementation with vitamin K.
Osteoporosis: The low down on vitamin K
There are two main forms of vitamin K.
Phylloquinone, also known as phytonadione, (vitamin
K1) is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90 per cent of the vitamin K in a typical Western diet.
The second form consists of menaquinones (vitamin K2), which make up about 10 per cent of Western vitamin K consumption and can be synthesised in the gut by microflora. Menaquinones can also be found in the diet in animal meat and fermented food products like cheese.
Osteoporosis: Reduce your risk of osteoporosis
Both vitamins K1 and K2 have been shown to play a role in bone health, influencing the secondary modification of osteocalcin, a protein needed to bind calcium to the bone matrix.
Some large human studies have tested the bone health benefits of calcium alone, calcium plus vitamin D and calcium plus vitamin D plus vitamin K. The latter has shown the best effect on osteoporosis.
A spokesperson for the UKs National Osteoporosis Society told NutraIngredients.com that people with osteoporosis have been found to have lower levels of vitamin K, indicating that it plays an important role in preventing this disease.
However according to US supplier PL Thomas, only K2 has so far been seen to have additional cardiovascular benefits. There is also evidence to suggest that K2 remains in the body for considerably longer than K1.
Based on the recent findings of the current review in the American Medical Association journal Archives of Internal Medicine, the authors suggest that individuals at risk of fracture be encouraged to consume a vitamin K rich diet.
Archives of Internal Medicine, 26 June 2006 Bolton Smith et al, Ann Nutr Metab 2001; 45, p 246; Braam et al, 2003, Calcif Tissue Int 72 Journal Proceedings of the National Academy of Sciences,