K2 includes several related compounds
Vitamin K2 refers to menaquinones with different side-chain lengths. Food sources can contain different forms, while vitamin K1 is a separate major dietary form. A database entry headed vitamin K may not provide the specific MK-7 amount needed for a direct comparison. [1][2]
Natto’s fermentation is particularly relevant
A food-focused review describes production of MK-7 during natto fermentation with Bacillus bacteria. The 2025 natto review contrasts its high MK-7 content with lower menaquinone quantities in foods including miso. These are composition distinctions, not proof that one serving treats osteoporosis. [2][3]
Miso does not have one dependable K2 value
The inspected reviews do not establish a standardized amount for every miso type, brand or serving. Ingredients, fermentation and the portion used can differ. Do not copy a natto value onto a bowl of miso soup merely because both foods involve fermented soy. [3][1]
Warfarin users need consistency and clinical advice
NIH warns that changes in vitamin K intake can affect warfarin treatment. Discuss a major change in natto, miso or K-containing supplement use with the anticoagulation team. A food’s traditional status does not make a large change irrelevant to treatment. [1]
Compare a real serving and the same measurement
Imagine a label gives total vitamin K for one food while an article reports MK-7 per hundred grams for another. Those values are not directly interchangeable. Identify the form, unit and actual serving before calculating which contributes more. [1][2]
| Detail | Why it matters |
|---|---|
| Miso versus natto | Different fermentation and composition |
| Total K versus MK-7 | Different measurements |
| Per 100 g versus serving | Different denominators |
| Warfarin treatment | Intake changes may alter anticoagulation |
Sources for this article
- Vitamin K - Health Professional Fact Sheet
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product. - Vitamin K: Double Bonds beyond Coagulation Insights into Differences between Vitamin K1 and K2 in Health and Disease - PMC
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product. - Habitual natto intake elevates serum MK-7 levels, enhances osteocalcin carboxylation, and supports bone density: a meta-analysis of Japanese evidence - PMC
Source consulted: 2026-09-21. This is a reference resource, not a claim that we conducted the studies or tested a product.