Vitamin K2 (MK-7)
Directs calcium to bones and away from arteries: essential when taking vitamin D3.
What is Vitamin K2 (MK-7)?
Vitamin K2 is a fat-soluble vitamin distinct from K1 (which is primarily involved in blood clotting). K2 activates proteins that control calcium distribution in the body, directing it into bones (via osteocalcin) and away from arterial walls (via matrix Gla protein). MK-7 (menaquinone-7) is the most bioavailable form and has the longest half-life in the body.
What does the evidence say?
A 2009 Rotterdam study (Geleijnse et al.) found high dietary K2 intake was associated with a 52% reduction in arterial calcification and a 57% reduction in cardiovascular mortality. A 2013 study by Knapen et al. found MK-7 at 180mcg/day significantly slowed arterial stiffness progression compared to placebo. Research also suggests a synergistic role with vitamin D3 for bone health and a potential role in testosterone synthesis.
Good evidence from several studies, but with some limitations in size, duration, or methodology.
Dosage guide
| Effective dose | 100–200mcg of MK-7 per day |
| Maximum dose | No established upper limit; studies use up to 360mcg without adverse effects |
| Timing | With a fat-containing meal. Often paired with vitamin D3. |
Best form to buy
MK-7 (not MK-4). MK-7 has a longer half-life (3 days vs 1.5 hours) and requires once-daily dosing. Natto (fermented soy) is the richest food source but is rarely consumed in the UK.
Who benefits most
Any man supplementing vitamin D3 at doses above 2,000 IU/day. Also relevant for men with cardiovascular risk factors or osteoporosis concerns.
Side effects and safety
Generally very safe. May interact with warfarin: if on blood thinners, discuss with your GP before supplementing.
“If you're taking vitamin D3, take K2 with it. This is a non-negotiable pairing in my view. The cardiovascular protection data is compelling and the risk is essentially zero at standard doses.”