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Catechins are bioactive compounds present in green tea. One well-known catechin, epigallocatechin gallate (EGCG), is a potent scavenger of reactive oxygen species and has demonstrated antioxidant, anti-inflammatory, and anticarcinogenic properties in both clinical and in vitro studies. Some evidence suggests that adding vitamin C to green tea might increase the bioavailability of the catechins present in green tea.
Consumers of green tea commonly add milk, lemon, or other substances to their tea. To assess the impact that these additives have on catechin bioavailability, the authors of the study added varying quantities of citric acid, BHT and EDTA (common preservatives), ascorbic acid (vitamin C), milk (cow’s, soy, and rice), and citrus juice (orange, grapefruit, lemon, and lime) to prepared tea. Then they subjected the tea formulations to simulated digestive processes and measured the amount of catechins they recovered.
They found that overall, green tea catechin recovery was poor, with more than 80 percent loss of catechins during digestion. Adding milk to tea increased catechin recovery considerably, but the greatest improvements were observed with the addition of vitamin C or citrus juices, the latter of which increased recovery to 98 percent.
Citrus juices contain bioactive compounds that might influence catechin recovery, but they are also rich in vitamin C. These findings suggest that consumption of green tea with vitamin C, especially in conjunction with other bioactive compounds in citrus juices, increases the recovery of the beneficial components present in the tea.