Taking calcium or vitamin D without vitamin K-2 is like hiring construction workers without giving them a blueprint. While Vitamin D3 helps your intestines absorb calcium into your bloodstream, Vitamin K-2 acts as your body’s calcium "traffic cop." It activates specific proteins that drive calcium directly into your bone matrix where you need it, preventing it from accumulating in your arteries and soft tissues where you do not.
Why Source Naturals Vitamin K2 Plus D3 Stands Out:
✓100 mcg of MenaQ7® (MK-7): Fermented menaquinone-7 that stays active in your bloodstream for days rather than hours.
✓Synergistic Vitamin D-3 (400 IU / 10 mcg): Enhances intestinal calcium transport and bone mineral deposition.
✓Dual-Action Defense: Protects arterial elasticity while promoting structural bone density.
✓Clean Formulation: Zero wheat, gluten, soy, dairy, egg, preservatives, or artificial flavorings.
The "Calcium Paradox": How Vitamin K-2 Directs Calcium Where It Belongs
For decades, health enthusiasts were told to simply supplement more calcium to keep bones dense. However, medical research discovered what physicians refer to as the calcium paradox: consuming calcium without proper regulatory nutrients can leave bones weak while accelerating calcium accumulation in blood vessel walls.
Vitamin K2 solves this dilemma through a biochemical process called carboxylation, which switches on two vital proteins in the human body:
1. Osteocalcin (The Bone Binder)
Produced by bone-building osteoblast cells, osteocalcin remains inactive until Vitamin K2 "turns it on." Once activated, it binds circulating calcium tightly into the hydroxyapatite matrix of your bones and teeth.
2. Matrix Gla-Protein (The Arterial Shield)
Matrix Gla-Protein (MGP) is the most potent inhibitor of soft-tissue calcification known in mammalian biology. Activated MGP prevents calcium from settling into smooth arterial linings, helping to maintain supple, flexible arteries.
What About Vitamin K1? Regular Vitamin K1 (phylloquinone), found in leafy greens like spinach, travels primarily to your liver to assist with blood clotting. It does very little for your bones or cardiovascular system. Vitamin K-2 (menaquinone-7) bypasses the liver and travels straight to vascular walls and skeletal tissue.
Peer-Reviewed Clinical Research Behind Vitamin K-2 MK-7
The dose and form of Vitamin K-2 in Source Naturals SN1922 reflect findings from major human clinical trials:
The Rotterdam Study: Cardiovascular Risk Reduction
In a landmark population study tracking 4,807 participants over 10 years, individuals in the highest tier of dietary Vitamin K-2 intake exhibited a 52% lower risk of severe aortic calcification and a 57% lower rate of coronary heart disease death compared to those with low K-2 intake. Vitamin K1 intake showed no correlation with heart health.
Citation: Geleijnse JM, Vermeer C, Grobbee DE, et al. Dietary intake of menaquinone is associated with a reduced risk of coronary heart disease: The Rotterdam Study. J Nutr. 2004;134(11):3100-3105. [PMID: 15514282]
Three-Year Double-Blind Bone Health Trial
A rigorous 3-year randomized trial led by Dr. Knapen examined 244 healthy postmenopausal women. Long-term supplementation with MenaQ7® menaquinone-7 significantly prevented the age-related decline in bone mineral density at the lumbar spine and femoral neck, while substantially improving bone strength.
Citation: Knapen MH, Drummen NE, Smit E, Vermeer C, Theuwissen E. Three-year low-dose menaquinone-7 supplementation helps decrease bone loss in healthy postmenopausal women. Osteoporos Int. 2013;24(9):2499-2507. [PMID: 23525894]
In a companion 3-year study evaluating arterial health via ultrasound, participants receiving long-term MK-7 demonstrated measurable improvements in carotid artery elasticity and decreased pulse-wave velocity, reversing the arterial stiffening common with age.
Citation: Knapen MH, Braam LA, Drummen NE, Bekers O, Hoeks AP, Vermeer C. Menaquinone-7 supplementation improves arterial stiffness in healthy postmenopausal women. Thromb Haemost. 2015;113(5):1135-1144. [PMID: 25694037]
Why MenaQ7® MK-7 Outlasts Other Forms of Vitamin K
Not all Vitamin K2 supplements are identical. Most basic options use synthetic short-chain MK-4 (menatetrenone), which has an elimination half-life of roughly 1.5 to 2 hours. To maintain active levels with MK-4, you must take large doses multiple times per day.
Source Naturals incorporates MenaQ7® (MK-7), a natural long-chain menaquinone derived from bacterial fermentation. Because of its side-chain structure, MK-7 stays active in your bloodstream for up to 72 hours (3 full days).
Feature
Vitamin K1 (Phylloquinone)
Vitamin K2 (MK-4)
MenaQ7® MK-7 (In SN1922)
Blood Half-Life
1 to 2 hours
1.5 hours
Up to 72 hours
Primary Target Tissue
Liver
Pancreas, Salivary Glands
Bones & Arterial Walls
Daily Dosing Frequency
Multiple daily
3 times daily (mg scale)
Once daily (100 mcg)
Extrahepatic Saturation
Poor
Moderate
Exceptional
Complete Supplement Facts & Ingredient Listing
Source Naturals adheres to Good Manufacturing Practices (cGMP) for consistent potency, purity, and tablet dissolution.
Supplement Facts
Serving Size: 1 Tablet | Servings Per Container: 60
Contains no yeast, dairy, egg, gluten, soy, or wheat. Contains no sugar, starch, salt, preservatives, or artificial colors, flavors, or fragrances. Suitable for vegetarians.
How to Take, Bioavailability Tips & Vital Safety Information
Suggested Daily Use
Take 1 tablet daily, preferably alongside a meal that contains dietary fats (such as avocado, olive oil, eggs, or nuts). Because Vitamins K-2 and D-3 are fat-soluble nutrients, dietary fat significantly stimulates bile acid secretion, accelerating absorption into the lymphatic system.
If you are currently taking prescription anticoagulant or antiplatelet drugs—specifically Warfarin (Coumadin®)—do NOT take Vitamin K-2 without direct physician approval.
Warfarin works by inhibiting Vitamin K recycling in the liver to lengthen clotting time. Supplementing Vitamin K-2 counteracts the therapeutic effect of warfarin and can alter your International Normalized Ratio (INR). Consult your cardiologist or hematologist prior to use.
Additional Precautions: If you are pregnant, planning to become pregnant, or breastfeeding, consult your healthcare provider prior to supplementation. Store bottle tightly closed in a cool, dry place. Keep out of reach of children.
Frequently Asked Questions (FAQ)
What is the difference between Vitamin K1, Vitamin K2 MK-4, and Vitamin K2 MK-7?
While Vitamin K1 regulates blood clotting in your liver and synthetic MK-4 leaves the body in a matter of hours, Menaquinone-7 (MK-7) has an extended 72-hour half-life. This allows MK-7 to circulate continuously throughout your bloodstream, maintaining full activation of calcium-regulating proteins in bone and vascular tissue around the clock.
Why is Vitamin D-3 combined with Vitamin K-2 in this Source Naturals formula?
Vitamins D3 and K2 operate in biochemical synergy. Vitamin D3 increases the absorption of calcium from food into your bloodstream, while Vitamin K2 directs that absorbed calcium into your skeleton and keeps it from hardening in arterial walls. Taking high doses of Vitamin D3 without Vitamin K2 can leave calcium unmanaged in circulation.
Does Source Naturals MenaQ7® contain soy?
No. While traditional natto-based Vitamin K2 is fermented from soybeans, the patented MenaQ7® utilized in this Source Naturals formula is manufactured through an allergen-free fermentation process. It is officially certified free of soy, gluten, dairy, egg, and wheat.
How long does it take for Vitamin K-2 to show noticeable benefits?
Biochemical activation of osteocalcin and Matrix Gla-Protein begins within hours of your first dose. However, structural benefits—such as increased bone mineral density and reduced arterial stiffness—are long-term physiological adaptations. Human clinical trials demonstrate measurable improvements in bone density and vascular flexibility over 6 to 12 months of consistent daily use.
What is the best time of day to take Source Naturals Vitamin K-2 Plus D3?
The best time is alongside your largest meal of the day containing healthy fats (such as breakfast or lunch). Because both Vitamin D3 and Vitamin K2 are lipophilic (fat-soluble), dietary fat increases gastrointestinal absorption by up to 50% compared to taking them on an empty stomach.
