Inclusion Criteria:

• Healthy elderly female subjects between 65 and 80 years of age.

General Exclusion Criteria:

• Subjects who participate in regular structured exercise more than 2 hours and 30 min per week or 1 hour and 15 min of vigorous exercise per week.
• Unwilling to comply with the follow-up schedule.
• Inability or refusal to give informed consent by the subject.
• Subject who takes multivitamins containing vitamin B3 derivatives in a dose > 200 mg/day.
• Participation in another investigational drug study within 1 year of treatment.

Laboratory Exclusion Criteria:

• Serum 25-hydroxyvitamin D < 15 ng/ml.
• Serum phosphorus > 5 mg/dL.
• Serum alkaline phosphatase 50% above normal limit.
• Serum aspartate transaminase 50% above normal limit.
• Serum calcium > 10.5 mg/dL.
• Estimated Glomerular Filtration Rate (eGFR) < 30 mL/min.
• Poorly controlled Diabetes Mellitus (HbA1c>8).

Clinical History Exclusion Criteria:

• Confirmed diagnosis of Diabetes Mellitus in use of insulin.
• Subjects presenting systolic BP > 180 mmHg or a diastolic BP > 90 mmHg on initial evaluation.
• Previous diagnosis of liver disease.
• Previous chronic kidney disease stage IV.
• Malignancy.
• Malabsorption syndrome.
• Hypo- or Hyperparathyroidism.
• Acromegaly.
• Cushing’s syndrome.
• Hypopituitarism.
• Severe chronic obstructive pulmonary disease.
• Congestive heart failure.
• Musculoskeletal disorder.
• History of rheumatoid arthritis.
• Previous gastric bypass surgery.
• Clinical history of osteoporotic fracture (spine, hip, or distal forearm) within past year.
• Extreme of BMI (≤ 18.5 kg/m2 or ≥ 40 kg/m2).

Medication Exclusion Criteria:

• History of methotrexate therapy.
• History of denosumab therapy.
• History of oral or inhaled corticosteroid use > 3 months.
• Current use of anticoagulants in general.
• Anticonvulsant therapy (within previous year).
• Sodium fluoride (any history).
• Pharmacological doses of thyroid hormone (causing decline of TSH below normal).
• Treatment within the past 3 years with bisphosphonates.
• Treatment within the past 3 years with parathyroid hormone.
• Treatment within the past 3 years with calcitonin.
• Treatment within the past 3 years with estrogen.
• Treatment within the past 3 years with selective estrogen receptor modulator.