Postmenopausal osteoporosis is one of the important medical disorders affecting women after menopause. It is characterized by bone loss and reduced bone strength. In turn, this leads to increased risk of fracture. Bone loss in postmenopausal women occurs when calcium leaks out of the bones. Supplementing calcium and vitamin D is considered as standard prophylactic measures against osteoporosis for postmenopausal women over age 50.

Currently, various formulations of calcium salt are under development for the effective supplementation of calcium. Pearlium/Effecti-Cal is a new formulation optimized for high solubility of calcium salt. Formulation A5 (the base formulation of Pearlium/Effecti-Cal) showed three fold higher retention of calcium in rats than calcium carbonate (the most popular calcium supplement). High retention of calcium allowed the reduction of orally administered calcium for the same effect. This can contribute to the reduction of gastrointestinal side effects such as constipation.

In postmenopausal women, bone mineral loss is reflected on the elevated level of bone turnover markers. In this study, the efficacy of Pearlium/Effecti-Cal will be assessed by the suppression of bone turnover markers. In addition, the safety of Pearlium/Effecti-Cal will be evaluated with a bowel function diary, which can capture the profile of constipation symptoms.

The participants will experience run-in period (two months) for removing the residual effect of previously taken health product on bone turnover. For the following treatment period (six months), one hundred and two participants will be allocated by chance into groups for the treatment of Pearlium/Effecti-Cal or active comparator (conventional calcium supplement).

Inclusion Criteria:

1. Female of age 40 to 85, inclusive
2. Have been postmenopausal for at least 3 years. Menopause is defined by a history of amenorrhea for at least 12 consecutive months since the end of the final menstrual period and plasma Follicle-stimulating hormone > 30 IU/L. In the case of hysterectomy, the date of the surgery is regarded as the end of the final menstrual period. Postmenopausal period is calculated from the end of the final menstrual period.
3. Ambulatory
4. Competent and willing to give signed informed consent

Exclusion Criteria:

1. Health conditions or any history that can invalidate the evaluation of bone mineral density (BMD) by dual energy x-ray absorptiometry
2. The lowest T-score in dual energy x-ray absorptiometry report less than the age-specific limit of T-score
3. A history of bilateral oophorectomy before age 40
4. A history of menopause before age 40
5. A history of malignancy within the past 3 years, except basal cell carcinoma of the skin
6. Current history of any medical disease that may be associated with the development of metabolic bone disease
7. Body Mass Index (BMI) < 18.5 kg/m2 or > 38.0 kg/m2 at the screening visit
8. Vigorous physical activities for more than 180 minutes/week
9. Any screening laboratory abnormality that exceeds the local laboratory's reference range by more than Investigators pre-specified limits
10. Use of medications or supplements which can affect bone or calcium metabolism
11. Use of any other investigational drugs during the past 1 month
12. Clinically significant and currently active hematological, endocrinological, cardiovascular, renal, hepatic, gastrointestinal psychiatric or neurological conditions.
13. Any other medical condition or reason that, in the Investigator's opinion, makes the participant unsuitable for this study
14. Mental incapacity or language barriers which preclude adequate understanding or cooperation
15. Unwillingness to comply with the requirements of the study protocol