Tea’s Hidden Benefit: Purifying Water Naturally

Researchers have discovered another compelling reason to enjoy tea: its natural ability to purify water. A team from Northwestern University found that tea leaves can absorb harmful metals like lead and cadmium from water, preventing their ingestion. While tea leaves should not replace traditional water filters, this study sheds light on the passive health benefits of this popular beverage.

The researchers, whose study was published in the journal ACS Food Science & Technology, note that tea’s unique property is not necessarily due to its composition, but rather its widespread consumption. “You could crush up various materials to achieve a similar metal-remediating effect, but that wouldn’t be practical,” said Benjamin Shindel, the study’s first author and an engineer at Northwestern University, in a university statement. “With tea, people don’t need to do anything extra. Just steep the leaves in water, and they naturally remove metals.”

This process occurs because heavy metal ions cling to the surface of tea leaves. To investigate this property, Shindel and his colleagues measured metal levels in heated solutions before and after steeping with various teas, tea bags, brewing methods, and steeping times. Their findings revealed several key observations, including the importance of steeping time in tea’s ability to filter heavy metals.

According to Shindel, “The longer the tea steeps, the more heavy metals it filters from the water. Some people brew their tea for seconds, but brewing it for longer periods or even overnight, like iced tea, can recover most or even all of the metal in the water.” The surface area of the tea leaves also plays a significant role, with higher surface areas providing more binding sites for metal ions.

When tea leaves are processed, they wrinkle and their pores open, increasing their surface area and ability to absorb heavy metals. Grinding the leaves also increases surface area, providing more capacity for binding. Additionally, tea bags can contribute to contaminant absorption, with cellulose bags absorbing a significant amount of heavy metals, whereas cotton and nylon bags had minimal absorption.

The researchers found that a typical cup of tea (one mug of water with one tea bag steeped for three to five minutes) could filter out approximately 15% of lead from the water, even if the water contains toxic levels of lead. While tea is not a solution to a drinking water crisis, this study provides practical insights that could impact future public health research.

As Shindel noted, “Across a population, if people drink an extra cup of tea per day, we might see declines in illnesses correlated with heavy metal exposure over time. Or it could help explain why populations with higher tea consumption have lower incidence rates of heart disease and stroke.” In essence, tea drinkers can continue enjoying their favorite beverage, knowing it’s providing an added health benefit.