I have heard reports
discussing recent studies identifying a role for vitamin K in processes other
than clotting. How is vitamin K involved in clotting and what other processes
may it be involved in?
Vitamin K is
a fat-soluble vitamin that exists in three forms, two of which are naturally
occurring. It is stored in the body’s fat tissue and liver and is best known
for its role in helping blood clot. In fact, the “K” comes from the German word
“koagulation”. Vitamin K has key functions in the blood coagulation pathway as
it makes one third of the proteins involved in the process. However, recent
data seems to point to a role for vitamin K in bone metabolism and possibly even
What are the
links between vitamin K and bone density?
Proper use of calcium in bones requires vitamin K- higher levels
are correlated with greater bone density, while lower levels are linked with
osteoporosis. Furthermore, one study found that osteoporosis
patients who suffer fractures have vitamin K levels that are much lower than
those of their age-matched controls. In clinical studies, both men and women
whose vitamin K intakes were among the lowest of those studied had a higher risk
of hip fracture than those whose intakes were among the highest. Furthermore,
long-term observation of post-menopausal women showed that in a given time
period, those who took vitamin K supplements not only suffered fewer fractures,
but also had lower rates of cancer occurrence, specifically non-Hodkins
The later needs further research.
How will I know if I am not getting enough vitamin K?
deficiency is rare because in addition to being abundant in leafy green
vegetables, vitamin K is made by the bacteria that are found in the intestines.
However, the body stores very little of it so it is important to have regular
dietary intake of vitamin K to avoid deficiency, which results in clotting
problems. Symptoms include bruising, nosebleeds, bleeding gums, blood in the
urine or stool, tar-like stools, and/or extremely heavy menstrual bleeding.
conditions can prevent the absorption of vitamin K. Therefore, individuals with
gallbladder or biliary disease, cystic fibrosis, celiac disease, Crohn’s
disease, liver disease, serious burns, or those using blood-thinners or on
hemodialysis, should be particularly aware of these symptoms.
Are there any risks to taking
vitamin K supplements?
taking anticoagulants such as warfarin (Coumadin) must keep their vitamin K
intake stable and thus should not begin a vitamin K supplement without an
explicit directive from their physician. Other medications that may be affected
by increasing your circulating vitamin K levels are antibiotics, dilantin,
orlistat, olestra and bile acid sequestrants. Aside from its effect on these
medications, there is no known toxicity associated with high doses of vitamin K
intake and supplements are well-tolerated. As with any nutritional regimen, you
should consult with your health care provider before starting vitamin K
M., (2008). Vitamin K Supplementation in Postmenopausal Women With Osteopenia (ECKO
Trial): a Randomized Controlled Trial. PLoS Medicine. 5 (10), e196.
W., (2005). Osteoporosis: the Role of Micronutrients. American Journal of
Clinical Nutrition. 81 (5), 1232S-1239S.