How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Vitamin K2
Vitamin K from fermented foods like natto (MK-7) or synthetic (MK-4). In postmenopausal women, it slows bone loss in some trials and not in others; on fractures, meta-analyses remain uncertain. To be avoided if taking anticoagulants.
Benefits
- In healthy postmenopausal women, 180 µg of MK-7 per day for three years slowed the decrease in bone mineral density of the lumbar spine and femoral neck (randomised placebo-controlled trial)
- Improves lumbar bone density in osteoporotic individuals: this is the conclusion of the meta-analysis on menatetrenone (MK-4) involving nearly 8,900 patients, which nevertheless considers the effect on fractures to be uncertain
- In patients with Alzheimer's disease, stroke or Parkinson's, menatetrenone reduced the risk of non-vertebral and hip fractures (meta-analysis of three trials), with no serious adverse effects
- Softens the arteries of postmenopausal women: three years at 180 µg of MK-7 per day improved arterial stiffness, especially in those whose arteries were the stiffest at baseline; a second one-year trial at the same dose points in the same direction
- In haemodialysis patients, 360 µg per day reduced the frequency, duration and severity of muscle cramps (crossover pilot placebo-controlled trial)
Precautions
If you are taking an oral anticoagulant (vitamin K antagonist), do not take it: in healthy volunteers, doses of MK-7 as low as 10 µg per day altered the INR in a significant proportion of them, and the authors conclude that it must be avoided during anticoagulant treatment. The menatetrenone meta-analysis notes a slight increase in adverse events. Outside of anticoagulant use, one year at 360 µg per day did not activate coagulation in dialysis patients, and 45 µg for eight weeks did not alter coagulation in healthy children. The limitations: regarding fractures, the 2019 meta-analysis considers the evidence insufficient, and the effect on bone density is no longer significant once biases are taken into account; the strong anti-fracture effect of an older meta-analysis comes from MK-4 in Japanese patients. In early-menopausal women, 360 µg per day for one year did not slow down bone loss. In elderly individuals who fall, one year at 200 or 400 µg per day improved neither balance nor physical function. Three years of MK-7 changed nothing in the body composition of postmenopausal women, and two years of K2 with vitamin D reduced neither heart fat nor inflammation in elderly men.
Recommended dosage
180 µg of MK-7 per day, the dosage used in three-year bone and artery trials; the selected trials range from 45 to 360 µg per day. The MK-4 form has been tested at 1.5 mg per day.
How to take it
- For whom: trials mainly involve postmenopausal women, osteoporotic individuals and patients (dialysis, neurological disorders). Very few concern young, healthy adults.
- Dosage: 180 µg of MK-7 per day in the three-year bone and artery trials; 360 µg per day in dialysis patients.
- Two forms: MK-7 is dosed in micrograms; MK-4 (menatetrenone) was tested at 1.5 mg per day for one year in Japanese postmenopausal women.
- Duration: effects on bones and arteries are measured over one to three years. In one year, 360 µg of MK-7 did not slow bone loss in early menopause.
- Under anticoagulant: to be avoided. In volunteers on oral anticoagulant treatment, 10 µg of MK-7 per day was already enough to shift the INR.
- Timing and meals: no study in this file compares morning to evening, nor intake during or between meals.
Did you know?
Even at 10 µg per day, eighteen times less than the dose in the bone trials, vitamin K2 (MK-7) was enough to shift the INR of volunteers on oral anticoagulant treatment.
What the studies say
This systematic review and meta-analysis evaluated the effects of menaquinone-7 (MK-7) supplementation on anthropometric measurements, glycemic indices, and lipid profiles. The results indicate that MK-7 may have beneficial effects on glycemic control, reducing insulin, HbA1c, and HOMA-IR. A desirable effect on total cholesterol was also noted, although further high-quality research is needed for consistent conclusions.
Nikpayam O, Jafari A, Faghfouri A, Pasand M, Noura P, Najafi M, Sohrab G. — Prostaglandins & other lipid mediators (2025) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more