What is the recommended daily intake of vitamin K-2 (menaquinone) in micrograms?

Recommended Daily Intake of Vitamin K-2

For healthy adults, the adequate intake (AI) for total vitamin K is 90 mcg/day for women and 120 mcg/day for men, though specific recommendations for vitamin K-2 (menaquinone) supplementation range from 100-200 mcg/day based on bone health research. 1, 2

Standard Dietary Reference Intakes

The established adequate intake levels are based on vitamin K1 (phylloquinone) requirements, as insufficient data exists to set separate recommendations specifically for vitamin K-2: 1

• Women: 90 mcg/day total vitamin K
• Men: 120 mcg/day total vitamin K
• General guideline: 1 mcg/kg body weight per day 1

These recommendations from EFSA and IOM apply primarily to vitamin K1, with the understanding that vitamin K-2 forms can contribute to meeting total vitamin K requirements. 1

Vitamin K-2 Supplementation for Bone Health

Research evidence supports higher doses of vitamin K-2 specifically for improving bone metabolism markers:

• Minimum effective dose: 100 mcg/day of menaquinone-7 (MK-7) significantly improves osteocalcin carboxylation, a marker of vitamin K adequacy in bone tissue 2
• Dose-response relationship: Daily intake of 50 mcg MK-7 showed minimal effect, while both 100 mcg and 200 mcg doses produced significant improvements in bone health markers 2
• Clinical osteoporosis treatment: Japan has approved vitamin K-2 at much higher therapeutic doses (typically 45 mg/day of MK-4) for osteoporosis treatment, though this represents pharmacological rather than nutritional dosing 3

Special Population Considerations

Infants and children require weight-based dosing: 1

• Infants up to 12 months on parenteral nutrition: 10 mcg/kg/day
• Older children: 200 mcg/day

Patients with malabsorption conditions (cystic fibrosis, celiac disease, short bowel syndrome) require higher supplementation: 1

• Infants with CF: 0.3-1 mg/day (300-1000 mcg/day)
• Older children and adults with CF: 1-10 mg/day (1000-10,000 mcg/day) depending on severity

Bariatric surgery patients after biliopancreatic diversion need: 1

• 300 mcg/day vitamin K included in multivitamin or separately

Safety and Toxicity

Vitamin K1 and K-2 are not associated with toxicity, making higher supplemental doses safe for most individuals: 1

• No established upper tolerable intake level exists for natural vitamin K forms
• Doses up to several milligrams daily have been used safely in clinical trials 1, 2
• The only contraindication is for patients taking vitamin K antagonists (warfarin), where consistent intake at recommended doses is actually beneficial for anticoagulation stability, though doses above 150 mcg may cause drug resistance 1

Practical Recommendations by Clinical Context

For general health maintenance in healthy adults: 90-120 mcg/day total vitamin K from diet and supplements meets basic requirements 1

For bone health optimization: 100-200 mcg/day of MK-7 form specifically, based on evidence showing improved bone metabolism markers at these doses 2

For individuals at risk of deficiency (fat malabsorption, chronic antibiotic use, liver disease): Start with 1-10 mg/day (1000-10,000 mcg/day) depending on severity and underlying condition 1

Important Caveats

The distinction between vitamin K-1 and K-2 matters clinically because menaquinones (K-2) appear more effective for bone health and have longer half-lives in circulation compared to phylloquinone (K-1). 4, 2 However, official dietary reference intakes do not yet distinguish between forms due to limited data when these guidelines were established. 1

Dietary sources of K-2 include fermented foods (natto is exceptionally high), certain cheeses, and animal products, while K-1 predominates in leafy green vegetables and vegetable oils. 5, 6 Intestinal bacteria synthesize some K-2, but this contribution appears insufficient to meet total requirements. 1