Vitamins K1 & K2

Vitamin K1 (phylloquinone, C₃₁H₄₆O₂) & Vitamin K2 (menaquinone-7 C₄₆H₆₄O₂)

Evidence: Strong

Vitamin K is a fat-soluble vitamin with two members in our formula: K1 (phylloquinone) from leafy greens and K2 (menaquinone-7), the highly bioavailable form that your own gut bacteria help produce. Both contribute to normal blood clotting, and vitamin K also supports the maintenance of normal bones, working hand in hand with vitamin D and calcium to direct calcium where it belongs.

There is a neat gut connection here too. K2 is one of the vitamins manufactured by a healthy microbiome, and emerging research is exploring vitamin K's broader role in the intestinal environment. Including both forms ensures you are covered regardless of how much your own microbes make.

PubMed indexes over 34,000 peer-reviewed papers on vitamin K.

Selected study 1 of 2

Lai Y, Masatoshi H, Ma Y, Guo Y, Zhang B. Role of Vitamin K in Intestinal Health. Frontiers in Immunology. 2022;12:791565. doi:10.3389/fimmu.2021.791565

Study summary

Study type: 2022 narrative review of animal, cell and limited human data on vitamin K and gut health.

Observed benefits: Higher vitamin K intake is associated with a more balanced microbiota and better markers of intestinal-barrier and antioxidant status across the studies reviewed.

Mechanisms: Vitamin K is the cofactor for gamma-glutamyl carboxylase, supports vitamin-K-dependent proteins, and appears to shape microbial composition.

Safety: No adverse events reported from supplementation; high vitamin K intake can interfere with vitamin-K-antagonist anticoagulants, so users on those medicines should consult a doctor.

Evidence strength: Promising but preliminary, resting mainly on mechanistic and animal work.

Selected study 2 of 2

Aaseth JO, Finnes TE, Askim M, Alexander J. The Importance of Vitamin K and the Combination of Vitamins K and D for Calcium Metabolism and Bone Health: A Review. Nutrients. 2024;16(15):2420. doi:10.3390/nu16152420

Study summary

Study type: Narrative review of cohort studies, randomised trials and meta-analyses on vitamin K, alone or with vitamin D.

Observed benefits: Adequate vitamin K, especially K2 alongside vitamin D and calcium, is associated with better bone-mineral density in the trials reviewed.

Mechanisms: Vitamin K activates osteocalcin and matrix-Gla protein, helping direct calcium into bone and away from soft tissue; vitamin D and K work synergistically.

Safety: Generally well tolerated; the main caution again concerns anticoagulant medicines.

Evidence strength: Moderate, supported by multiple trials and meta-analyses with varied doses and durations.