Northwestern University researchers have found that brewing tea can naturally adsorb heavy metals such as lead and cadmium, filtering out these contaminants from beverages. The study, published in ACS Food Science & Technology, highlights the potential for tea consumption to reduce exposure to heavy metals.
“We’re not suggesting that everyone starts using tea leaves as a water filter,” said Vinayak P. Dravid, the study’s senior author. “For this study, our goal was to measure tea’s ability to adsorb heavy metals.”
The research team tested various types of tea, including black, green, oolong, white, chamomile, and rooibos teas. They also examined the differences between loose-leaf and commercially bagged tea. The experiments involved creating water solutions with known amounts of metals like lead and then adding tea leaves for different steeping times.
Findings revealed that finely ground black tea leaves were most effective at removing metal ions due to their high surface area. Longer steeping times resulted in more significant removal of contaminants.
Benjamin Shindel, the study's first author, noted that while other materials could achieve similar effects, tea is practical because it is widely consumed. “With tea, people don’t need to do anything extra. Just put the leaves in your water and steep them,” he said.
Different types of tea bags were also tested. Cellulose bags proved most effective at absorbing contaminants without releasing microplastics into the water. Cotton and nylon bags absorbed minimal amounts of metals.
“When comparing different varieties of tea, finely ground black tea leaves absorbed slightly more metal ions than whole leaves,” Shindel explained.
The researchers estimate that typical tea preparation can remove about 15% of lead from drinking water under certain conditions. However, they caution against relying on this method during a water crisis or in areas with high contamination levels.
Shindel mentioned that increasing daily tea consumption might contribute to public health benefits by reducing illnesses associated with heavy metal exposure over time.
The study was supported by the U.S. Department of Energy and Northwestern University’s Paula M. Trienens Institute for Sustainability and Energy.