A 2025 review linked Vitamin K₂‘s effects on vascular health with cognitive function:

“Cardiovascular disease (CVD) is negatively correlated with cognitive health. Arterial stiffness, in particular, appears to be a critical factor in the functional and structural brain changes associated with aging. We review the association between vitamin K and cerebral function, discussing novel developments regarding its therapeutic role in arterial stiffness and cognitive health.

Among the non-invasive measures of vascular stiffness, pulse wave velocity (PWV) is considered the gold standard. PWV measures arterial stiffness along the entire aortic pathway, providing a reliable, feasible, and accurate assessment of vascular health. Arterial stiffness, as measured by PWV, is negatively associated with total brain volume, brain atrophy, and cognitive function. Pathogenic mechanisms responsible for vascular stiffness recently shifted from collagen and elastin to the differentiation of vascular smooth muscle cells to osteoblastic phenotype, which is triggered by oxidative stress and inflammation, membrane mechanotransduction, lipid metabolism, genetic factors, and epigenetics.

Vitamin K-dependent proteins (VKDPs) rely on vitamin K to undergo γ-glutamylcarboxylation, a modification essential for their biological activity. This family of proteins includes hepatic VKDPs such as prothrombin, FVII, FIX, and FX, protein S and protein C as well as extrahepatic VKDPs such as matrix Gla-protein (MGP), which is involved in inhibiting vascular calcification, and osteocalcin, which plays a role in bone mineralization.

Structural differences between K1 and K2 influence their bioavailability, absorption, bioactivity, and distribution within tissues. Compared to vitamin K1, the K2 subtype menaquinone-7 (MK-7) has a significantly longer half-life, accumulates more effectively in blood, and exhibits greater biological activity, particularly in facilitating the carboxylation of extrahepatic VKDPs. Circulating dephosphorylated, uncarboxylated Matrix Gla protein (dp-ucMGP), a marker of extrahepatic vitamin K deficiency, could represent a novel therapeutic target for mitigating both arterial stiffness and cognitive decline.

Vascular calcification and arterial stiffness may represent pathophysiological mechanisms underlying the onset and progression of cognitive decline. Vitamin K deficiency is a key determinant of arterial health and, by extension, may influence cognitive function in the elderly.

To elucidate potential therapeutic benefits of MK-7 supplementation on cognitive function, future randomized controlled trials (RCTs) are needed. These trials should focus on using optimal dosages (>500 μg/day), ensuring long follow-up periods, and utilizing the most bioactive form of vitamin K (MK-7).”

https://www.frontiersin.org/journals/aging-neuroscience/articles/10.3389/fnagi.2024.1527535/full “The role of vitamin K₂ in cognitive impairment: linking vascular health to brain health”

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A coauthor Dr. Katarzyna Maresz took time on her weekend to answer a few questions:

1. Regarding the second paper of Part 2 of Vitamin K2 – What can it do?:

Hello Dr. Maresz. Did this trial ever happen? “Effects of Combined Vitamin K2 and Vitamin D3 Supplementation on Na[18F]F PET/MRI in Patients with Carotid Artery Disease: The INTRICATE Rationale and Trial Design” I haven’t seen a followup mention of it since 2021.

“Hello. The study never started. The capsules were produced for the study, but the research center experienced delays. Unfortunately, I’m afraid it won’t proceed. Regarding studies on aortic stenosis and vitamin K2, BASIC II has been completed, and the data from this pilot study are currently under analysis. (https://pubmed.ncbi.nlm.nih.gov/29561783/). There is also published study with K1: https://www.ahajournals.org/doi/10.1161/CIRCULATIONAHA.116.027011

2. Thank you! In your recent review of cognitive function and K₂ (above), what influenced the heuristic that a >500 mcg K₂ dose should be pursued in future RCTs?

“The optimal vitamin K dosage depends on the target population. Research in kidney patients has shown that 460 mcg daily was insufficient, that is why have hypothesis that at least 500 mcg should be used. The ongoing VIKIPEDIA study is using 1,000 mcg daily in peritoneal dialysis patients. In healthy young individuals, 180-360 mcg was effective in improving vitamin K status (British Journal of Nutrition (2012), 108, 1652–1657) . However, a one-year clinical study found that 180 mcg daily was sufficient for women but not for men. Additionally, older adults and individuals with metabolic disorders may require higher doses for optimal benefits. So it is pretty complicated situation. We do not have good marker of extrahepatic K status. dp-ucMGP seems to be valuable from CV perspective.”

3. Regarding Fat-soluble vitamin competition:

Thank you again Dr. Maresz! Would any consideration be given to dosing K₂ separately from dosing another fat-soluble vitamin? A 2015 in vitro study found that vitamins D, A, and E outcompeted K₁ intake when simultaneously dosed. I inferred from the one capsule of D₃-K₂ produced for the canceled trial that isn’t that much of a problem with K₂?

“You are right, the key findings suggest that vitamin D, E, and K share common absorption pathways, leading to competitive interactions during uptake. However, I’m afraid we do not have human data. The majority of studies have focused on vitamin K2 alone. Recent research combining K2 and D3 showed an improvement in vitamin K status. Example: https://pubmed.ncbi.nlm.nih.gov/35465686/ or increase in D level: https://pubmed.ncbi.nlm.nih.gov/39861434/. We do not know if VKDP activation or absorption of D would be more effective if K2 were not supplemented with D3 at the same time. Unfortunately, I doubt anyone will fund such a study, as clinical trials are very expensive. In vitro data will always raise questions regarding their relevance to human physiology. In my opinion, for patients to fully benefit from optimal vitamin K status, vitamin D levels should also be optimized, as both have synergistic effects.”