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A comprehensive vitamin K formula providing both K1 and two forms of K2 (MK-4 and MK-7) at meaningful doses. Vitamin K is critical for calcium metabolism — directing calcium to bones rather than arteries. Life Extension is one of the few brands that includes MK-4 at 1000mcg alongside MK-7, recognizing that these forms have different tissue distribution and half-lives.
Life Extension Super K scores 81 for providing the most comprehensive vitamin K formulation available at a reasonable price. The combination of K1, MK-4, and MK-7 is evidence-informed and reflects that different K vitamers have different tissue targets and half-lives. Zero hype penalty — Life Extension has a decades-long track record of science-first formulation and publishes research citations for their products. The value score (82) reflects the excellent 90-softgel count at $0.24/serving. The formulation score (84) is the highest because this product addresses a genuine nutritional gap — most people are K2-deficient and most multivitamins do not include K2 at all.
Vitamin K plays an essential role in calcium metabolism through carboxylation of osteocalcin (directing calcium to bones) and matrix Gla protein (preventing arterial calcification). Knapen et al. (2013, Thrombosis and Haemostasis) 3-year RCT showed 180mcg MK-7 improved bone mineral content and femoral neck strength in postmenopausal women. Knapen et al. (2015) found MK-7 supplementation decreased arterial stiffness in healthy postmenopausal women. Cockayne et al. (2006, Archives of Internal Medicine) meta-analysis found vitamin K supplementation reduced fracture risk. The distinction between K forms matters: K1 (phylloquinone) primarily supports coagulation, MK-4 has short half-life but accumulates in brain and reproductive tissues, and MK-7 has a long half-life that maintains steady-state blood levels (Schurgers et al., 2007). Life Extension Super K includes all three, recognizing their complementary tissue distribution.
| Ingredient | Dose | Verdict |
|---|---|---|
| Vitamin K1 (Phylloquinone) | 1500mcg | Optimal |
| Vitamin K2 (MK-4, Menaquinone-4) | 1000mcg | Adequate |
| Vitamin K2 (MK-7, Menaquinone-7) | 100mcg | Optimal |
Save $3.90/month (54%)
by switching to NOW Foods Vitamin C-1000
Vitamin K supplements are contraindicated for people taking warfarin or other vitamin K antagonist anticoagulants — this is a serious interaction. The MK-4 dose (1000mcg) is well below the 45mg (45,000mcg) used in Japanese clinical trials for osteoporosis treatment, though it likely provides more than dietary intake. Life Extension brand loyalty can border on cult-like, and some products in their line are overhyped — though Super K is not one of them. Requires fat for absorption (fat-soluble vitamin) — must be taken with a meal. The soft gel contains soybean oil, which some people prefer to avoid.
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