Mercola writes

MK-4 is a synthetic product, very similar to vitamin K1, and your body is capable of converting K1 into MK-4. However, MK-4 has a very short biological half-life of about one hour, making it a poor candidate as a dietary supplement.

Given that Mercola claims generally deserve skepticism I ask myself whether that's true. Unfortunately, drug-bank stores no information about its half-life.

1 Answer 1



After this extremely short tl;dr: to be fair, we do not know for sure. Because it seems to be quite complex, if not complicated. And that means the claim is at least very dubious.

25 years ago Vitamin K metabolism would have only considered K1 (phylloquinone) and discuss its role in haemostasis. That has changed and the other derivates are now under very interested –– but also admittedly interesting –– investigation. Having just one such unsourced opinion is unlikely to present anything resembling correct or useful information, since the metabolism and pathways for these substances are apparently interdependent, too.

All of the above studies addressed the question of how phylloquinone is transported in the circulation but when three different forms of vitamin K were ingested simultaneously they were found to behave differently. In a comparative study, healthy volunteers ingested a mixture of 2 μmol of phylloquinone, MK-4 and MK-9 with a test meal and the serum and lipoprotein profiles of each vitamer measured for up to 48 h. In agreement with previous studies, phylloquinone was found mainly in TRL and most was cleared from the circulation within 8 h. No more than 17% and 18% of circulating phylloquinone appeared in the LDL and HDL fractions respectively with the greatest proportions between 8–24 h. MK-4 concentrations were lower at all times than those of phylloquinone and were distributed almost equally between TRL, LDL and HDL up to 4 h. Thereafter, although circulating MK-4 was still being cleared quickly, the proportion in LDL increased sharply until at 8 h some 80% of that remaining was present in LDL.* MK-9 had the lowest of all serum concentrations over the first 6 h; it was initially present only in TRL but began to appear in LDL by about 8 h after ingestion and remained there for at least 48 h. MK-9 was never found in HDL. The reasons why MK-4 and MK-9 were found at lower serum concentrations remain unclear though the authors speculate that it could be due to faster uptake by tissues relative to phylloquinone, at least for MK-4.
Martin J. Shearer & Paul Newman: "Metabolism and cell biology of vitamin K", Thromb Haemost. 2008 Oct;100(4):530-47. DOI:10.1160/TH08-03-0147

The claim is not only unsourced. It also displays a curious reasoning for assaying usefulness. If a substance is cleared from the blood plasma quickly, as the claimant seems to orient his reasoning on, that does not mean a thing. Is it broken down or excreted before being used or just used up completely or converted into other useful substances? Case A would bring some sense into the claim, case B completely invalidates it.

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