Wednesday, January 19, 2011

Green Tea Extracts Are Safe


For postmenopausal women with osteopenia (low bone mineral density), practicing tai chi and/or taking green tea polyphenols appears to be safe. Further, practicing tai chi by itself or in combination with green tea polyphenol supplements may improve quality of life; however, taking green tea supplements by themselves has no significant improvement in quality of life. This is according to a recent NCCAM-funded study published in BMC Complementary and Alternative Medicine. Osteopenia may precede osteoporosis, a bone disease characterized by reduced bone strength that can lead to fractures—a significant cause of disability in older people.

Previous clinical studies have suggested that tai chi—a traditional Chinese practice involving physical movement, mental focus, and deep breathing—has beneficial effects on bone health. Likewise, animal research has indicated that green tea polyphenols (substances rich in antioxidants) also may have bone-protective effects. However, there is limited information on the long-term safety of green tea supplements in people as well as several reports concerning their adverse effects on liver and kidney function. To further build on this evidence and to evaluate the effect of tai chi in combination with green tea polyphenol supplements, NCCAM-funded researchers investigated the safety and impact on quality of life of these interventions in postmenopausal women with osteopenia. (This study is part of a larger research project that is investigating the effects of green tea polyphenols and tai chi on bone health in postmenopausal women with low bone mineral density. Results of other findings from the study—bone, inflammation, and stress parameters—will be published at a later date.)

Researchers from Texas Tech University randomly assigned 171 women to receive green tea polyphenols (500 mg daily); green tea polyphenols plus tai chi training; placebo pills (500 mg starch daily); or placebo pills plus tai chi training over a 24-week period. The tai chi training consisted of three 60-minute sessions per week. Researchers measured participants' depression (mood) and general health status, as well as liver and kidney function throughout the study. Participants in the tai chi groups reported significant beneficial effects in quality of life in terms of improving their emotional and mental health. The researchers found that green tea supplements did not significantly affect participants' liver enzymes or kidney serum levels and had no effect on quality of life.

The researchers noted that this is the first placebo-controlled, randomized study to evaluate the safety of long-term use of green tea supplements in postmenopausal women. Based on these findings, the researchers concluded that green tea polyphenols at a dose of 500 mg daily for 24 weeks, alone or in combination with tai chi, appears to be safe in postmenopausal women with low bone mineral density.


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