Want a flavorful beverage with a lot less lead? Try tea. According to a team of researchers from Northwestern University, tea leaves and bags adsorb lead, trapping lead ions on their surfaces and filtering them from drinking water during the process of tea brewing.
“For this study, our goal was to measure tea’s ability to adsorb heavy metals,” said Vinayak Dravid, a member of the research team and a Northwestern professor, according to a press release. “By quantifying this effect, our work highlights the unrecognized potential for tea consumption to passively contribute to reduced heavy metal exposure in populations worldwide.”
Limiting Exposure to Lead
Long-term exposure to lead and other heavy metals is tied to a variety of symptoms, including headaches, insomnia, and irritability, as well as to issues like heart disease and stroke. Though there are many ways to encounter these heavy metals, one is by drinking contaminated water.
Looking for methods to limit our exposure to these contaminants, the Northwestern team turned to tea, testing the adsorption of different types, including black, green, and oolong teas, among others.
These teas “have a high active surface area,” said Benjamin Shindel, another member of the research team and a Northwestern graduate student at the time of the research, according to the release, “which is a useful property for an adsorbent material.”
The researchers revealed that black teas adsorbed more heavy metals than non-black teas. They also found that ground leaves were best at removing contaminants.
“When tea leaves are processed into black tea, they wrinkle and their pores open,” Shindel said in the release. “Those wrinkles and pores add more surface area. Grinding up the leaves also increases surface area, providing even more capacity for binding.”
Reporting the results in ACS Food Science & Technology, the team says that tea could curb lead consumption over time. “I’m not sure that there’s anything uniquely remarkable about tea leaves as a material,” Shindel added in the release. “But what is special is that tea happens to be the most consumed beverage in the world.”
Read More: Lead Poisoning Is Still a Major Problem — Here’s How it Impacts Our Health
Tea Types, Bags, and Times
Using water contaminated with lead, chromium, copper, zinc, and cadmium, the researchers steeped the teas anywhere from a few seconds to 24 hours. They then compared the contamination amounts from before and after the teas were brewed, to determine the amount of heavy metal adsorption that had occurred.
According to the team, the type of tea bag affected the removal of lead and other heavy metals, with cellulose-bagged leaves being much adsorbent than cotton- or nylon-bagged ones. Also impactful was the teas’ steeping time, with teas that were brewed for a longer amount of time adsorbing more metal ions than teas that were brewed for a shorter amount of time.
“Any tea that steeps for longer or has higher surface area will effectively remediate more heavy metals,” Shindel said in the release. “Some people brew their tea for a matter of seconds, and they are not going to get a lot of remediation. But brewing tea for longer periods or even overnight — like iced tea — will recover most of the metal or maybe even close to all of the metal in the water.”
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Cup Concentrations
The team says that a typical serving of black tea, brewed with a tea bag and a typical amount of water with a lead concentration of 10 parts per million, can cut concentrations of lead by around 15 percent, if brewed for around three to five minutes.
“Ten parts lead per million is obviously incredibly toxic,” Shindel said in the release. “But with lower concentrations of lead, tea leaves should remove a similar fraction of the metal content in the water.”
Of course, tea isn’t the only solution to heavy metal contamination that’s out there. “We’re not suggesting that everyone starts using tea leaves as a water filter,” Dravid said in the release. Still, the research reveals important insights for limiting our overall exposure to lead and other heavy metals.
“Across a population, if people drink an extra cup of tea per day, maybe over time we’d see declines in illnesses that are closely correlated with exposure to heavy metals,” Shindel said in the release. “Or it could help explain why populations that drink more tea may have lower incidence rates of heart disease and stroke than populations that have lower tea consumption.”
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Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
