Study Objective: To determine whether Natto supplementation in women immediately after menopause might prevent severe bone loss

Study population: Women 50 - 60 years, 1-5 years after menopause

Study Design: Double-blind, placebo-controlled, randomized controlled trial. A "phase II" clinical trial.

Instruments Used to Measure Therapeutic Response: Lunar Prodigy DEXA bone densitometer

Study Treatment Group: Daily supplementation with Vitamin K2, "NATTO"

Study Control Group: Identically-looking placebo medication

Duration of treatment: 12 months

Duration of Subject Participation in Study: 12 months Assessment of Therapeutic response: Given an expected reduction of bone mass density of - 1.1% annually in the placebo group, the minimum clinically significant difference between the groups is 0.3 percentage points. The trial is therefore powered to detect a reduction in annual bone mass loss of 0.3 percentage points in the treatment group.

Numbers of Evaluable Subjects Required: 304 Maximum # Subjects 334

Inclusion Criteria:

• Women living in the city of Tromsø, not using hormone replacement therapy, 1-5 years after menopause.

Exclusion Criteria:

• History of hip fracture
• Bone disease affecting bone mineral density
• Use of vitamin K antagonists
• Significant co-morbidity that makes it difficult to obtain BMD measurements
• Use of hormone replacement therapy or other therapy that influence bone remodeling