Effects of Epigallocatechin-3-O-Gallate on Bone Health

Tea is one of the most consumed beverages in the world, belonging to the category of compounds known as tannins and flavonoids. One of the polyphenols found in large amounts in green tea leaves (Camellia sinensis) is epigallocatechin-3-O-gallate (EGCG). Though EGCG has shown some pharmacological effects, to date, it has not been utilised as a therapeutic agent. This is attributed to the fact that EGCG lacks adequate stability, and it is known to degrade through epimerization or auto-oxidation processes, especially when it is exposed to light, temperature fluctuations, some pH values, or the presence of oxygen. Consuming green tea with EGCG can alleviate the effects of bone diseases, such as osteoporosis, and support faster bone regeneration in the case of fractures. Therefore, this review focuses on the current state of research, highlighting the effects of EGCG on bone biology, such as enhancing osteoblast differentiation, promoting bone mineralisation, improving bone microarchitecture, and inhibiting osteoclastogenesis through the modulation of the RANK/RANKL/OPG pathway. Additionally, EGCG exerts antioxidant, anti-inflammatory, and dose-dependent effects on bone cells. It also downregulates inflammatory markers (TNF-α, IL-1β, and COX-2) and reduces oxidative stress via the inhibition of reactive oxygen species generation and the activation of protective signalling pathways (e.g., MAPK and NF-κB). Studies in animal models confirm that EGCG supplementation leads to increased bone mass and strength. These findings collectively support the further exploration of EGCG as an adjunct in the treatment and prevention of metabolic bone diseases. The authors aim to present the relationship between EGCG and bone health, highlighting issues for future research and clinical applications.