Vitamin K is in an odd position on the supplement shelf.  It’s essential, but largely ignored next to more well-known nutrients like Vitamin D, magnesium or zinc. More confusing still is the fact that there are two Vitamin Ks, K1 and K2, which function totally differently in the body.  When we think of Vitamin K, we mostly think of K1, found in green leafy vegetables and responsible for clotting.  But Vitamin K2 is the real director of physiology, staying in the body longer and having its effects on bones, arteries, heart and even brains. 

1. I take K2 to help put calcium where it belongs 

Calcium is not automatically good or bad. It depends where it ends up. 

In the bones and teeth, calcium is essential. In the arteries, heart valves, kidneys, and soft tissues, excess calcium deposition is not something we want. Vitamin K2 helps activate proteins that guide calcium into the skeleton and away from soft-tissue calcification. 

Bone-building cells called osteoblasts produce a protein called osteocalcin. Osteocalcin  requires K2 to become activated. Once carboxylated by K2, osteocalcin can bind free-floating calcium in the blood and incorporate it into the bone matrix. Think of K2 as the traffic director, routing calcium away from your arterial walls and toward your skeleton. 

This is one of the reasons I think of K2 as a partner to vitamin D. Vitamin D helps us absorb calcium. K2 helps activate the proteins that help manage calcium. Taking vitamin D without paying attention to K2 feels, to me, like increasing supply without improving distribution. 

The research here is solid. A 2024 meta-analysis and systematic review published in Bone & Joint Research found that Vitamin K supplementation primarily supports bone health by enhancing the carboxylation of osteocalcin — exactly this mechanism. Longer-term studies, including a three-year randomized trial, have shown that low-dose MK-7 supplementation helps decrease bone loss in postmenopausal women. And a broader review in Frontiers in Public Health concluded that K2 shows meaningful efficacy in the prevention and management of osteoporosis. 

It’s not only postmenopausal women who need to worry about bone density.  It can be a problem in elderly men as well.  The evidence that K2 contributes to that feels worth acting on. 

2. I take K2 to keep calcium out of my arteries 

Your body produces a protein called Matrix Gla Protein (MGP), which lives in the walls of your blood vessels. Its job is to grab circulating calcium and prevent it from depositing into arterial walls — essentially, it’s your body’s built-in defense against vascular calcification. The catch? MGP is secreted in an inactive form. To become active and actually do its job, it needs Vitamin K2 as a cofactor. 

Without sufficient K2, MGP just sits there, inert, while calcium quietly hardens in places you don’t want it. Researchers have described activated MGP as the most potent known inhibitor of vascular calcification — and there’s clinical evidence to back that up. In one randomized trial, participants taking MK-7 (a  form of Vitamin K2) maintained arterial flexibility over the study period, while the placebo group’s arteries measurably stiffened. That’s not a small thing. 

This is also why researchers have flagged a concern about taking high-dose Vitamin D3 without K2. D3 increases calcium absorption from your gut — which is great if that calcium ends up in your bones, but potentially problematic if you don’t have enough active MGP to keep it out of your arteries. See below for my recommendation. 

3. I take K2 to maintain my brain health 

My brain is near and dear to my heart (well, not actually near, but you know what I mean).  Anything I can do to hold back the twin ravages of Parkinson’s Disease and aging is worth my investigation.  And so when I read that “deficiency of Vitamin K2 is associated with PD progression” in the journal Brain Sciences, I started to pay more attention to the literature. 

A 2024 review published in Frontiers in Aging Neuroscience examined the relationship between Vitamin K2 and cognitive function. The authors noted that K2 may be vital for preserving brain health, and the proposed mechanism is interesting: vascular calcification and arterial stiffness — the things K2 already helps prevent — are themselves significant risk factors for cognitive decline. By keeping arteries flexible and blood flow healthy, K2 may indirectly protect the brain. 

There’s also evidence that K2 plays roles in the nervous system beyond vascular effects. The research is preliminary, but in a supplement with an otherwise excellent safety profile and multiple established benefits, “promising early evidence for brain health” is a reasonable bonus to factor in. 

4. I take K2 because modern diets are often light on it 

K1 is relatively easy to obtain if someone eats leafy greens. K2 is a different story. The richest food source is natto, a fermented soybean food popular in Japan — and not exactly a staple in most American kitchens. Some K2 is found in aged cheeses, egg yolks, butter, liver, and certain fermented foods, but intake varies tremendously. 

That makes supplementing K2 a sensible choice, especially for people already taking vitamin D, concerned about bone health, or thinking seriously about healthy aging. 

The form I usually think about is MK-7, because it has a longer half-life than MK-4 and is commonly used in studies at microgram doses. Specifically, I take a combination of Vitamin D3 5000 iu and Vitamin K2 (MK-7) 180 mcgm. 

One note of caution. Anyone taking warfarin or other vitamin K-sensitive anticoagulation should not casually add K2 without medical supervision, because changes in vitamin K intake can affect anticoagulant control.  For everyone else, though, Vitamin K2 provides a safe and, evidently, effective means of enhancing and maintaining good health.

Search for Vitamin K2 at The Rothfeld Apothecary