That Tea Bag Is Purifying Your Water

In the tea vs. coffee debate, some coffee fans hail the way coffee grounds trap heavy metals in water. Now, tea fans can clap back. Tea leaves, whether loose or in a bag, absorb heavy metals like lead and arsenic, meaning that when you brew a cup, you're essentially filtering your water, new research suggests. Following up on research that found absorbents derived from tea waste soaked up cadmium, zinc, and nickel, Northwestern University PhD student Benjamin Shindel and colleagues experimented with different teas, brewing methods, and steeping times to come up with what the Washington Post calls "the purest cup" of the most consumed beverage in the world.

Researchers heated water solutions containing lead, chromium, copper, zinc, and cadmium, then added tea leaves, allowing them to steep for a few seconds up to 24 hours, per Smart Water Magazine. They found steeping one cup of black tea for five minutes resulted in a 15% reduction in lead, regardless of the lead concentration. But the more brew time, the better purification. "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," Shindel, lead author of the study published Monday in ACS Food Science & Technology, tells the magazine.

Though ground tea leaves were better purifiers than whole leaves owing to the additional surface area, and cellulose tea bags performed far better than nylon and cotton tea bags, again due to the higher surface area of the material, such benefits were "marginal compared to the benefit of having more time," Shindel tells the Post. "We're not suggesting that everyone starts using tea leaves as a water filter," senior study author Vinayak P. Dravid tells Smart Water. But "our work highlights the unrecognized potential for tea consumption to passively contribute to reduced heavy metal exposure." Shindel notes tea might also absorb "other contaminants," per the Post. (Heavy black tea drinkers have a lower risk of death.)