Prevention of Early Postmenopausal Bone Loss With Lactobacillus Reuteri

Inclusion Criteria: * Postmenopausal women, 45 years or older, within 1-4 years from their last menses. * Vitamin D levels above 25 nmol/L. * Signed informed consent. * Stated availability throughout the entire study period. * Ability to understand study instructions and willingness to adhere to the protocol. Exclusion Criteria: * Bone mineral density of \< -2.5 combined with a fracture risk assessment tool (FRAX) score of 20% or higher for major osteoporotic fracture. * Severe osteoporosis, defined as bone mineral density of \< -3.0 in either the total hip, femur neck or lumbar spine L1-L4. * Vertebral fracture (grade II or III) diagnosed using lateral spine imaging with DXA. * Untreated hyperthyroidism or hyperthyroidism within the last 5 years. * Known untreated hyperparathyroidism. * Rheumatoid arthritis. * Diagnosed with disease causing secondary osteoporosis, including chronic obstructive pulmonary disease, inflammatory bowel disease, celiac disease, or diabetes mellitus. * Recently diagnosed malignancy (within the last 5 years). * Oral corticosteroid use. * Previous (within the last 5 years) use of antiresorptive therapy, including systemic hormone therapy (estrogen), bisphosphonates, strontium ranelate or denosumab. * Systemic skeletal disease (including e.g. Paget's disease and osteogenesis imperfecta). * Any systemic disease that could affect bone loss, as judged by the investigator. * Use of teriparatide (current or during the last 3 years). * Participation in other clinical trials. * Current antibiotics treatment or within the last 2 months prior to inclusion. * Current and within the past 2 months use of probiotic supplement * Vitamin D deficiency (25-OH vitamin D\<25 nmol/l) * Hypo- or hypercalcemia. * Osteosynthesis materials in both lower legs (tibia).