Green tea and cocoa powder are known around the world for their powerful antioxidant properties, and both are rich in catechins — a class of chemical compounds with antioxidant and anti-inflammatory properties.
Now, researchers at the University of São Paulo's Public Health School (FSP-USP) argue that guarana (the seeds of a tropical shrub) is another worthy antioxidant source, containing more than ten times the amount of catechins found in cocoa powder.
"Guarana has always been seen above all as a stimulant, especially by the international scientific community, because of its high caffeine content,” Lina Yonekura, the principal investigator of the research and assistant professor at Kagawa University's School of Agriculture in Japan, said in a press statement.
"This pioneering assessment of the absorption and biological effects of its catechins in human volunteers should foster interest in guarana as a functional food on the part of scientists, the market, and society in general."
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To come to this conclusion, the researchers conducted a month-long study in two stages. They recruited volunteers who were healthy, but slightly overweight with at moderately higher risk of cardiovascular disease.
The volunteers were instructed to take guarana each morning before breakfast by preparing a daily drink with 3 g of guarana powder in 300 ml of water.
The researchers designed the procedure as such that would ensure that each participant acted as his or her own control, and the effect of guarana was measured one hour after the participants drank the guarana drink on day 1 and day 15. They assessed how guarana affected oxidative stress markers, as well as a detailed evaluation of the subjects’ absorption of catechins and their metabolites. Finally, the team also performed a single cell gel electrophoresis (SCGE), which is a technique for analyzing DNA damage in individual cells due to various factors, like oxidative stress.
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"All these markers depend on the presence of catechins in the bloodstream," Yonekura said. "The improvement in the parameters we assessed was associated with a rise in the concentration of plasma catechins after guarana intake, showing that guarana was indeed responsible for this effect."
Further, the guarana catechins strengthened the cells’ native antioxidant enzymes, thereby protecting them from oxidative damage caused by outside factors.
"These results are exciting, suggesting that the bioavailability of guarana catechins is equal to or greater than that of green tea, cocoa and chocolate catechins," Yonekura concluded.
The team hopes these results strike an interest in guarana, since Brazil is basically the only country that produces it on a commercial scale, they say.
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Editor's note (8/29): Based on misinformation published in the press release, this article previously stated that guarana contains over 10x the amount of catechins found in green tea. It has been updated to clarify that guarana contains 10x the amount of catechins found in cocoa powder. We apologize for any confusion.