Vitamin k is a fat
soluble vitamin and is essential for cardiovascular health and strong bones. It
exists in two natural forms-vitamin K1 and K2. Vitamin K1 is known as
phylloquinone and found in green vegetables and plants, while vitamin K2 is
called menaquinone and is found in eggs, cheese, fermented foods such as
Japanese natto, and meat. In addition, the synthetic form is labeled as vitamin
Since not much is
known about the bioavailability of these two forms of vitamin K, Toshiro Sato
and colleagues conducted a study to determine the menaquinone-4 (MK-4) and
menaquinone-7 (MK-7) bioavailability in 10 healthy Japanese women.
Bioavailability refers to the amount of drug that reaches the circulation. The study was published in the Nutrition Journal, 2012.
During the study, a
single dose of menaquinone-4 (MK-4) and menaquinone-7 (MK-7) was given to
healthy females in the morning with breakfast. Vitamin K levels in the blood were measured just before taking
the medication and 2, 4, 6, 8, 10, 24, 48, and 72 after medication intake. The scientists observed that menaquinone -4
(MK-4) was not traced in the serum of volunteers at any given point of time
while menaquinone -7 (MK-7) reached maximum serum level in 6 hours and was
traceable up to 48 hours.
In another study,
women were administered a daily dose equivalent to the Recommended Dietary
Intake of either MK-4 or MK-7 for a week and vitamin K levels were estimated
It was observed that
MK-4 supplementation did not raised serum levels of MK-4 while MK-7 supplements
raised serum level of menaquinone-7 (MK-7) considerably.
The researchers concluded that the administration of MK-4
did not alter the serum vitamin K level while MK-7 supplements increased the
serum level of MK-7 and hence can be used in treating vitamin K deficiency
Comparison of menaquinone-4 and menaquinone-7
bioavailability in healthy women; Toshiro Sato et al; Nutrition Journal 2012