The general recommendation is to get about 100 micrograms of Vitamin K1 from our diet, because this is enough to activate blood clotting. The different types of Vitamin K2, mostly MK-4 and MK-7, have been studied for their beneficial effects for osteoporosis and for the prevention of arterial calcification. Vitamin K1 have been left out of this conversation, usually being thought of as a useless molecule in this regard. There have been a few studies where they compared Vitamin K1 to the popular forms of K2 and it turns out, not only is it not useless, it is actually superior in many ways.

Why is Vitamin K1 considered ineffective? 

In normal circumstances, if we get enough Vitamin K1, we can convert it into MK-4. The problem is some medications block this conversion, and in these cases K1 is not effective. Warfarin is a widely used anticoagulant medication, that works by blocking Vitamin K. In many studies that were aimed to discover the effectiveness of Vitamin K1, the participants also recieved drugs that block it’s effects. Where Vitamin K1 was given in the correct dose, and it wasn’t blocked by other medications, it was just as effective as both MK-4 and MK-7, in some cases even more effective. Lets take a look at a study that compared K1 with MK-4.

K1 vs K2 MK-4 R2 

In this randomized controlled trial, they looked at the effects of Vitamin-K in 381 postmenopausal woman, with healthy bones. One group received 1 mg of Vitamin K1 once a day, the other group 15 mg of MK-4 three times a day. There was a placebo group, and all groups received Vitamin D3, and calcium as well. 1 mg of Vitamin K1, is 10 times higher than the recommended daily intake, but still it is easily obtained even from diet alone. This isn’t the case for the total 45 mg of MK-4, which is impossible to obtain from food, as even the richest sources only contain a few hundred micrograms of MK-4 per 100 grams.  

The results 

Vitamin K1, even though it was given only once a day, in much less quantity, activated the Vitamin K dependant proteins just as effectively as the high dose MK-4. Both forms of Vitamin K reduced the levels of the inactive undercarboxylated osteocalcin protein to one third in the first month. The question is if the much cheaper Vitamin K1, taken once a day, is just as effective as the more expensive MK-4 taken three times a day, why would anyone bother taking MK-4 directly? The study was sponsored by a Japanese MK-4 producing company, so no wonder that after such disappointing results, there weren’t any further studies comparing the two forms. 

Since the study was only 1 year long and the participants didn’t have osteoporosis, they haven’t looked at fracture risks. There weren’t significant changes in bone mineral density, however this doesn’t mean Vitamin K didn’t have a beneficial effect through other mechanisms. In the ECKO-trial 5 mg K1 reduced fracture risks by more then 50% in postmenopausal woman. R3 

What about MK-7?  

In a 2012 study also looking at postmenopausal woman, they compared the effectiveness of 100 mcg of K1, to 100 mcg of MK-7. R4 They also received Vitamin D3 and calcium, but this time they had two control groups, and one of the control groups didn’t get any Vitamin D3. Both Vitamin K groups had increased bone mineral density compared to the control groups. 

It is quite suprising that such a low dose of K1 was effective for the bones, and that it produced similar results to the same dose of MK-7, that is generally considered much more effective.   

If someone is not taking medications that interfere with the actions of Vitamin K1, than based on these studies K1 is just as effective as the more expensive MK-4, and MK-7, and it is a lot easier to obtain enough even through our diet. Unfortunately this is probably the reason why it hasn’t been studied as well.