Mention vitamins A to E, and most people will know why they need them and what foods to find 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.
However, several ingredient suppliers have started offering vitamin K in recent months, suggesting that they see a market for stepping up its use in dietary supplements – particularly as the baby boom generation enters the age bracket where it starts to become more concerned with age-related health problems, including osteoporosis and heart disease.
Their timing may be good. Just last week a meta-analysis of studies of vitamin K and bone health published in peer reviewed journals found that supplementation is associated with increased bone mineral density (BMD) and reduced fracture incidence. The reduction in fracture incidence was also striking, with an approximate 80 percent reduction in hip fractures.
Despite this, the researchers said there was a need for large, pragmatic randomised clinical trials to confirm the results before supplementation could be recommended.
Results of small study
But recommended or not, is the public primed and ready for more vitamin K?
In a small email survey conducted by NutraIngredients.com last week, 56 percent of respondents said they had heard of vitamin K, but less than one percent said they take vitamin K supplements. It is unlikely that the remainder are making a conscious effort to include vitamin K in their diet (although they may be consuming it incidentally), since only 2 percent correctly identified any dietary sources.
As to vitamin K’s role in health, one percent of respondents were aware of its role in bone health and one percent of its role in preventing blood clots.
The survey involved 39 adults aged between 20 and 70 years, mostly European residents.
There has also been some confusion in the industry over the different forms of vitamin K, with suppliers offering NutraIngredients.com differing accounts.
Main forms of vitamin K
In summary, there are two main forms of vitamin K: phylloquinone, also known as phytonadione (vitamin K1), which is found in green leafy vegetables such as lettuce, broccoli and spinach, and makes up about 90 percent of the vitamin K in a typical Western diet; and 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 (MK-n: with the n determined by the number of prenyl side chains) can also be found in the diet; MK-4 can be found in animal meat, MK-7, MK-8, and MK-9 are found in fermented food products like cheese, and natto is a rich source of MK-7.
Both 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; its mechanism is different from, but synergistic with, the other two. (Bolton Smith et al, Ann Nutr Metab 2001; 45, p 246; Braam et al, 2003, Calcif Tissue Int 72).
However, according to US supplier PL Thomas, only K2 has so far been seen to have additional cardiovascular benefits by promoting promotes matrix Gla-protein, which inhibits vascular calcification. There is also evidence to suggest that K2 remains in the body for considerably longer than K1.
Improving bone health
A spokesperson for the UK’s 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”.
She said that people who eat a healthy balanced diet will be doing their best by their bones. A survey conducted by the society earlier this year to assess changing dietary habits over the last 20 years found that there was a trend towards cutting out dairy, without identifying alternative sources of calcium.
Moreover, many people said they did not think about nutritional value when preparing a meal at home.
Source: Decision News Media
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