The new study looked at three tea compounds called epigallocatechin (EGC), gallocatechin (GC), and gallocatechin gallate (GCG), and found that EGC produced the greatest bone boosting potential.
"Our study has provided the first laboratory evidence on the bone promotion effects of the green tea catechin EGC as was demonstrated by the promotion of osteoblastic differentiation and inhibition of osteoclast formation,” wrote researchers from the Chinese University of Hong Kong report their findings in the Journal of Agricultural and Food Chemistry.
Osteoblasts are cells responsible for bone formation, while osteoclasts are cells which break down bone, leading to resorption and weakening.
The study is consistent with data from epidemiological studies. A study published in the American Journal of Clinical Nutrition (Oct. 2007, Vol 86, pp. 1243-1247) reported that bone mineral density levels were 2.8 per cent greater in tea drinkers than non-tea drinkers, suggesting the beverage has the potential to aid in the prevention of osteoporosis.
The condition is currently second only to cardiovascular disease in terms of global healthcare burden, according to the World Health Organisation, affecting some 200 million people today but the number of sufferers is set to increase steadily with growing numbers of elderly living longer, and obesity adding extra strain on bones.
Green tea contains between 30 and 40 per cent of water-extractable polyphenols, while black tea (green tea that has been oxidized by fermentation) contains between 3 and 10 per cent.
The four primary polyphenols found in fresh tealeaves are epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin.
The Hong Kong based researchers used rat cells to study the effects of EGC, GC, and GCG on bone health.
EGC was found to stimulate bone mineralisation, while simultaneously inhibiting the formation of osteoclasts. The other catechins were found to have a significantly weaker effect, said the researchers.
“The present study illustrated 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,” wrote the authors.
"Our observations would serve as groundwork for further studies,” they concluded.
Source: Journal of Agricultural and Food Chemistry
Published online ahead of print, ASAP Article, doi: 10.1021/jf901545u
"Effects of Tea Catechins, Epigallocatechin, Gallocatechin, and Gallocatechin Gallate, on Bone Metabolism"
Authors: C.H. Ko, K.M. Lau, W.Y. Choy, P.C. Leung