Brewing benefits: Tea's surprising role in heavy metal removal

Researchers from Northwestern University in Evanston, USA, discovered that brewing tea naturally adsorbs harmful heavy metals, including lead and cadmium. According to the Polish Press Agency, metal ions adhere to the surface of the tea leaves and remain trapped until the used leaves or tea bag are disposed of.

Vinayak Dravid, the senior author of the study, highlights that the researchers aimed to measure tea's capacity to adsorb heavy metals. Dravid emphasized that their research reveals the overlooked potential of tea consumption in helping to lower heavy metal exposure on a global scale.

Benjamin Shindel, the first author of the study, adds that tea leaves have a large active surface area, a useful property for an adsorptive material, making tea leaves well-suited for quickly releasing flavouring chemicals into the water.

Shindel pointed out that tea's uniqueness lies in being the world's most widely consumed beverage. While various materials could be shredded to achieve a similar metal removal effect, they may not be practical. In contrast, tea requires no extra effort—simply brewing the leaves in water naturally eliminates metals.

The research included various types of teas, such as black, green, oolong, white, and herbal teas like chamomile and rooibos. It also tested the differences between loose leaf tea and tea bags. The results showed that cellulose tea bags are more effective at adsorbing metals than cotton or nylon ones.

It also turns out that brewing time plays a crucial role in tea’s ability to remove heavy metals. The longer the tea is brewed, the more contaminants are removed. Shindel points out that brewing for extended periods, even overnight, can remove most metals from the water.

The expert explained that briefly brewing tea for a few seconds has little impact on heavy metal levels. However, allowing the tea to steep for a longer period or even overnight, as with iced tea, can effectively remove most, if not all, metals from the water.

Scientists estimate that brewing tea can remove about 15 per cent of lead from drinking water. Shindel suggests that regular tea consumption might help reduce illnesses associated with heavy metal exposure.

Shindel suggested that increasing daily tea consumption by just one cup could, over time, lead to a reduction in illnesses linked to heavy metal exposure.

"Or it might help explain why populations that drink more tea could have lower rates of heart disease and stroke than populations that drink less tea," he noted.