The study was the work of Dr Ping Chung Leung and colleagues from the Institute of Chinese Medicine at the Chinese University of Hong Kong, and you can read about it in the Journal of Agricultural and Food Chemistry where a web version appeared last month.
Other studies have already suggested that chemicals in green tea benefit health in many ways, for example by preventing cancer and heart disease, but this is the first study to pinpoint which of those chemicals may also improve bone health by stimulating formation and slowing the breakdown of bone.
In humans, as in many organisms, bone is not a dead tissue but a living dynamic metabolic system that relies on a delicately maintained balance between bone formation and bone resorption. Cells called osteoblasts make bone while cells called osteoclasts resorb it.
For the study, the researchers exposed a group of cultured rat osteoblast-like cells to three catechin chemicals for several days. The chemicals were epigallocatechin (EGC), gallocatechin (GC), and gallocatechin gallate (GCG), all main components of green tea.
They found that one catechin in particular, EGC, stimulated the action of a key enzyme that promotes bone growth by up to 79 per cent.
The effect of boosting EGC also increased the level of bone mineralization in the cells, which strengthens bones.
They also found that EGC weakened the activity of osteoclasts, tipping the delicate bone metabolism balance away from resorption to formation.
The researchers also noted that the catechins did not appear to cause toxic effects in the bone cells.
They concluded that these findings showed:
"That the tea catechins, EGC in particular, had positive effects on bone metabolism through a double process of promoting osteoblastic activity and inhibiting osteoclast differentiations."
Osteoporosis is a condition where the density and quality of bone is reduced, increasing the risk of fracture.
According to the International Osteoporosis Foundation, for the year 2000, there were an estimated 9 million new osteoporotic fractures worldwide, of which 1.6 million were at the hip, 1.7 million were at the forearm and 1.4 million were clinical vertebral fractures.
Europe and the Americas accounted for just over half of all these fractures, while most of the remainder were in the Western Pacific region and Southeast Asia.
Although usually affecting women more often than men, in China there is a higher incidence of hip fractures in men than women.
"Effects of Tea Catechins, Epigallocatechin, Gallocatechin, and Gallocatechin Gallate, on Bone Metabolism."
Chun Hay Ko, Kit Man Lau, Wing Yee Choy and Ping Chung Leung.
J. Agric. Food Chem, 2009, 57 (16), pp 7293-7297.
Publication Date (Web): August 4, 2009 (Article)
Source: American Chemical Society, International Osteoporosis Foundation.
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