Cancer is a leading cause of the global disease burden, with mortality second only to Cardiovascular diseases. In 2019, there were 23.6 million cases and 10 million deaths from various cancers across 204 countries and regions. The global cancer burden is expected to continue increasing, with projections estimating 28.4 million cancer cases by 2040. Diet is believed to be an effective approach for preventing certain cancers.
Catechins are biologically active Polyphenol components found in fresh Tea leaves or Green Tea, and they are the primary contributors to the health benefits of tea. Fresh tea leaves typically contain four phenotypic catechins: (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG). EGCG is the most abundant catechin in fresh tea leaves, accounting for over 40% of total catechin content.
Many studies have shown that tea catechins possess anticancer properties. However, the impact of tea catechins and tea consumption on cancer risk remains inconclusive and controversial.
Epidemiological and in vivo studies suggest that tea catechins exhibit anticancer effects against various types of cancer, including gynecological cancers, digestive tract cancers, brain gliomas, hepatobiliary cancers, and lung cancer. Catechins inhibit the proliferation and metastasis of cancer cells, act as antioxidants to scavenge free radicals, enhance immune function, and synergize with anticancer drugs, involving multiple signaling pathways.
Despite a large number of in vivo and in vitro studies demonstrating the anticancer effects of tea catechins, inconsistent results have been observed and reported, such as a seven-year (1995-2001) population-based cohort study in Japan involving 41,440 individuals aged between 40 and 79 years, which did not find direct evidence linking green tea consumption to reduced lung cancer risk.
What causes these inconsistencies in research findings?
1. Metabolic and/or chemical changes in ingested catechins may be significant factors influencing the anticancer effects of tea and catechins.
2. Interactions between catechins and some drugs can reduce drug bioavailability, potentially diminishing therapeutic efficacy.
Exploring the potential of tea catechins in anticancer drug development should focus on the following areas: (1) Metabolism of ingested catechins in the gastrointestinal tract and developing methods to protect catechins from degradation or transformation; (2) technologies to improve catechin bioavailability, such as encapsulation and nanolization; (3) novel catechin formulations with synergistic anticancer effects.
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