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How do milk, sugar, and other sweeteners impact the antioxidant levels of teas?
Tea, especially black tea, is the world’s most popular beverage. But do common additives such as milk and sugar negatively impact black tea’s antioxidant activity?
With the help of funding from the Tea Research Foundation of Kenya, researchers in Africa performed tests to identify any changes in antioxidant activity when milk and popular sweeteners are added to black tea-because their potential impacts have “hardly been investigated.”
Mice were assigned to drink one of five different Kenyan teas before analysis of antioxidant levels in their blood, liver, brain, and kidney tissues. Teas were prepared with or without a number of additives: cow’s milk, refined white sugar, honey, and stevia powder.
Perhaps unsurprisingly, green teas yielded the most polyphenols and catechins, and black teas produced the most thearubigins and theaflavins. But the total quantity of these antioxidants often changed in sweetened teas. When milk was added to tea at levels above 2%, tea antioxidant activity significantly decreased-especially in black teas. Such losses are likely related to interactions between tea antioxidants and milk proteins, which have been documented in earlier research. Antioxidants were also challenged by sugar and honey in a concentration-dependent manner, but the full extent of how sucrose (a major constituent in these products) may impact antioxidants remains to be fully understood.
Stevia did not influence on antioxidant activity in plain teas and milk teas, at 0.1 and 0.3 g, and this suggests that stevia may be a preferred sweetener for companies that want to market sweetened teas for maximal potential health benefits.
The outcomes of this study reveal just how sensitive tea antioxidants are, and they also provide insight on a very specific antioxidant: glutathione. Glutathione in blood plasma of mice was generally highest two hours after tea consumption, and the researchers believe this indicates “the need to repeatedly take tea every two hours to maximize its potential health benefits.”
Further studies, they say, are still warranted to understand optimum intake levels for the various antioxidants found in tea.