High doses of phytochemicals in teas and supplements could be unhealthy
Chemical Research in Toxicology
Those phytochemicals — natural plant-based compounds that give fruits and vegetables a reputation as healthy food — could be unhealthy if consumed in high doses in dietary supplements, teas or other preparations, scientists in New Jersey have concluded after a review of studies on the topic.
In their article, scheduled for the current issue of ACS's Chemical Research in Toxicology, a monthly journal, Chung S. Yang and colleagues analyze available data on the toxic potential of polyphenols. That group of dietary phytochemicals includes flavonoids, whose suggested beneficial effects in fruits and vegetables include prevention of heart disease and cancer. The data was from studies done in humans and laboratory animals.
The report cites specific examples of toxic effects, including reports of liver, kidney, and intestinal toxicity related to consumption of high doses of green tea-based dietary supplements. The risk of such toxicity may be greater in individuals taking certain medications, or with genetic traits, that increase the bioavailability of phytochemicals, the researchers said. Citing the need for new studies on the topic, the report concludes: "Only when such data are compared to the evidence for beneficial health effects can a balanced judgment be made regarding the potential utility of these compounds for disease prevention and treatment."
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