• attrition rate, compliance [ Time Frame: 24 weeks ] [ Designated as safety issue: Yes ]
  

• bone turnover biomarkers, oxidative stress damage biomarker, biomechanical response [ Time Frame: 24 weeks ] [ Designated as safety issue: No ]
  

This is a 24-week, randomized, and placebo-controlled intervention trial to investigate the effects of green tea polyphenols (GTP) and Tai Chi (TC) on relevant primary and secondary endpoints in postmenopausal women with osteopenia. Women at least 2 years after menopause, with osteopenia, will be recruited primarily from local senior independent/assisted living facilities, municipal senior community centers, and obstetrics and gynecology clinics. After screening, qualified participants will be matched for age and will be randomly assigned to one of the four treatment groups: placebo, GTP, placebo+TC, and GTP+TC. During the 24-week intervention, all participants will be provided with calcium and vitamin D daily. The participants in the placebo group will receive medicinal starch for 24 weeks. The GTP participants will receive GTP for 24 weeks. The placebo+TC participants will receive both placebo and TC treatments for 24 weeks. The GTP+TC participants will receive both GTP and TC treatments for 24 weeks. Participants will receive the primary and secondary outcome measures at baseline, 6, 12, and 24 weeks. The primary outcome measures are concentrations of bone biomarkers. The secondary outcome measure is a biomarker of oxidative stress DNA damage. Investigators evaluating the endpoints will be blinded to intervention allocation.

Inclusion Criteria:

• Women at least 2 years after menopause (to ensure established postmenopausal status).
• Sedentary at baseline.
• Normal laboratory evaluation, thyroid function, hepatic function, renal function.
• Osteopenia.

Exclusion Criteria:

• History of scoliosis, severe osteoarthritis, etc., or other spinal disease that may result in anatomy unsuitable for accurate bone densitometry.
• History of cancer with some exceptions.
• History of metabolic bone disease.
• Beginning a regimen of any estrogen recently.
• Having used anabolic steroids, calcitonin, calcitriol, alfacalcidol, etc.
• Fluoride treatment at a dose greater than 1 mg/day any time.
• History of glucocorticoid treatment.
• Any previous treatment with bisphosphonates.
• Uncontrolled intercurrent illness such as symptomatic congestive heart failure, myocardial infarction or stroke, hypertension, or terminal illness.
• Physical conditions that preclude participation of exercise intervention.
• Cognitive impairment.
• Depression.
• History of malabsorption syndrome and uncontrolled diabetes mellitus.