Not medical advice. I am a software engineer, not a physician. This page documents my own protocol and the research I read while building it. Talk to a qualified clinician before changing your supplementation, diet or any treatment. Lab reference ranges quoted here vary by laboratory and by individual.
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Vitamin D3 and vitamin K2 are two of the most important fat-soluble nutrients in human health, and their synergy is critical. D3 (cholecalciferol) is technically a secosteroid hormone precursor that influences over 1,000 genes — far more than a simple vitamin. K2 (menaquinone-7) is the traffic controller for calcium: it activates the proteins that direct calcium into bones and teeth while keeping it out of soft tissues like arteries. Taking D3 without K2 increases calcium absorption but without proper routing, potentially contributing to arterial calcification. This is why they must always be supplemented together.
D3 is converted in the liver to 25-hydroxyvitamin D (calcidiol), then activated in the kidneys to 1,25-dihydroxyvitamin D (calcitriol) — the active hormone. Calcitriol binds to the vitamin D receptor (VDR), a nuclear receptor present in virtually every cell in the body. It regulates calcium and phosphorus absorption in the gut (increasing calcium absorption by 30-40%), modulates over 1,000 gene targets involved in immune function, cell proliferation, and differentiation. D3 deficiency is associated with increased risk of autoimmune disease, cancer, cardiovascular disease, and all-cause mortality.
D3 activates the innate immune system by inducing cathelicidin, a potent antimicrobial peptide produced by macrophages and epithelial cells. Simultaneously, it modulates the adaptive immune system by shifting the T-helper cell balance away from pro-inflammatory Th1/Th17 responses toward regulatory T-cells, reducing the risk of autoimmune overreaction. This dual action — enhancing pathogen defense while preventing autoimmune damage — makes D3 uniquely important for immune regulation.
K2 activates two critical calcium-dependent proteins through carboxylation. Osteocalcin is produced by osteoblasts and, when carboxylated by K2, binds calcium and incorporates it into the bone matrix, directly increasing bone mineral density. Matrix Gla Protein (MGP) is the most potent inhibitor of arterial calcification known; when activated by K2, it prevents calcium from depositing in arterial walls, heart valves, and kidneys. Without K2, these proteins remain inactive (undercarboxylated), and calcium absorbed via D3 can end up in arteries instead of bones.
The D3+K2 synergy: D3 increases calcium absorption from the gut. K2 activates the two proteins that direct where that calcium ends up: osteocalcin, which binds it into bone, and matrix Gla protein, which inhibits its deposition in arteries. MK-7 is the preferred K2 form because its 72-hour half-life maintains stable blood levels with a single daily dose, unlike MK-4 which has a half-life of only 1-2 hours.
| Parameter | Detail |
|---|---|
| Product | NATURELO Vegan Vitamin K2 + D3 |
| Dose | 5,000 IU D3 + 100 mcg K2 (MK-7) |
| Timing | With breakfast (fat-containing meal) |
| Form | Plant-based D3 (lichen-derived) + MK-7 (natto-derived) |
| Duration | Daily, ongoing |
See the full supplement stack for timing relative to other supplements and meals.
van Ballegooijen, A. J., et al. (2017). The synergistic interplay between vitamins D and K for bone and cardiovascular health. Int J Endocrinol, 2017, 7454376. — Comprehensive review demonstrating that combined D3+K2 supplementation improves bone mineral density and reduces arterial calcification more effectively than either vitamin alone. PubMed 28768407
Aranow, C. (2011). Vitamin D and the immune system. J Investig Med, 59(6), 881-886. — Establishes D3's role in activating cathelicidin antimicrobial peptides and modulating T-cell differentiation, with deficiency linked to increased autoimmune and infectious disease risk. PubMed 21118827
Knapen, M. H., et al. (2013). Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int, 24(9), 2499-2507. — 3-year RCT showing 180 mcg/day MK-7 significantly decreased age-related decline in bone mineral density and improved bone strength indices. PubMed 23525894
| Test | Why It Matters | Link |
|---|---|---|
| Vitamin D (25-OH) | The primary circulating form; optimal range 40-60 ng/mL for immune and bone health. Below 30 ng/mL is deficiency; above 80 ng/mL may indicate excess | Lab Tests |
| Calcium (serum + ionized) | D3 increases calcium absorption; monitoring prevents hypercalcemia. Optimal serum calcium: 8.5-10.5 mg/dL | Lab Tests |
A 2025–2026 review in the International Journal of Molecular Sciences investigated the pharmacological properties of vitamin D and K2 for cardiometabolic risk modulation, finding that co-supplementation may reduce coronary calcification more effectively than either vitamin alone. A substudy of the AVADEC trial examined the effects of vitamin K2 and D3 supplementation on epicardial adipose tissue and systemic inflammation over 24 months — while high-dose K2 and D3 reduced dp-ucMGP levels (a marker of vascular vitamin K status), they did not significantly affect epicardial adipose tissue or systemic inflammation markers. Clinical studies confirm that daily D3 administration (at least 2,000 IU) provides more stable serum 25(OH)D concentrations than intermittent boluses, with a threshold of 75 nmol/L associated with reduced cardiovascular disease risk. A clinical trial (NCT07199829) evaluating response to vitamin D3 and K2 supplementation is ongoing in 2026.
NATURELO Vegan Vitamin K2 + D3 — 5,000 IU D3 + 100 mcg K2 (MK-7), 60 vegetarian capsules. Price: $30.14. Buy on iHerb