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 K3.
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.
AdvertisementDuring 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 subsequently.
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 ailments.
Comparison of menaquinone-4 and menaquinone-7 bioavailability in healthy women; Toshiro Sato et al; Nutrition Journal 2012