Anyway, here are two studies on vitamin K, one on K1 and the other on Mk-4.
In a case-cohort designed study analyzing data from 296 people with extreme coronary artery calcium (CAC) progression, compared with data from 561 healthy controls, low serum vitamin K1 was significantly associated with CAC progression in anti-hypertension medication users. According to the authors, "intervention trials are needed to determine whether improving serum vitamin K1 reduces CAC progression, especially in hypertensives."
This was an interesting study because K1 is typically not associated with cardiovascular benefits. However, I do remember reading a study a few years back that reported something similar. It makes sense that with enough K1, our cardiovascular system would benefit (by way of reduced arterial calcification), it's just that the poor absorption of K1 and its very short biological half-life don't make it a good source to get the full benefits from this nutrient. Nonetheless, some will always be better than none!
Source: Association between circulating vitamin K1 and coronary calcium progression in community-dwelling adults: the Multi-Ethnic Study of Atherosclerosis
The other study looked at MK-4, a specific form of K2. In a randomized, double-blind, placebo-controlled trial involving 48 participants (aged 50-65 years), "low-dose" (1500 mcg/day) MK-4 supplementation over 6-12 months improved bone quality in postmenopausal women by decreasing the serum ucOC (undercarboxylated osteocalcin, which is inactive osteocalcin) and pentosidine (biomarker for advanced glycation end-products) concentrations, without any substantial adverse effects. The baseline concentrations of ucOC were high in both groups. After 6 and 12 months, the serum ucOC concentrations were significantly lower in the MK-4 group than in the control group. In the control group, there was no significant change in serum pentosidine concentrations. In the MK-4 group, the concentration of pentosidine at 6 and 12 months was significantly lower than at baseline. The forearm bone mineral density was significantly lower after 12 months than at 6 months in the control group. Research suggests that over the long-term, 1500 mcg daily supplementation of MK-4 may have positive effects on the various markers of bone turnover and bone mineral density (BMD) promoting bone health in healthy postmenopausal women.
This is also interesting since MK-4, when studied for bone-related benefits, was previously studied in extremely high doses (we're talking 45,000 mcg/day, in divided doses). This study used a much smaller dose and found benefit.
Source: Low-dose vitamin K2 (MK-4) supplementation for 12 months improves bone metabolism and prevents forearm bone loss in postmenopausal Japanese women
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