A new study revealed that tea leaves can extract heavy metals from water, which significantly reduces the amount of lead and other hazardous compounds that people could be consumed without knowing it.
Recent research has highlighted various ways to reuse used tea leaves, from biofuels to the elaboration of gluten -free cookies. However, this study shows a benefit to public health in a habit already rooted in millions of people. According to estimates, about 5 billion cups of tea in the world are consumed every day.
“You can see the implications”said Vinayak Dravid, scientist of materials from the University of the Northwest and author of the study published this week. “How often do we have thousands of millions of people at our disposal?”
In many countries, water used to prepare tea is contaminated with lead due to old pipes. In the United States, 9 million homes obtain water through pipes containing lead, according to the United States Environmental Protection Agency (EPA). Lead is especially dangerous for children, since their exhibition can cause development delays and behavioral problems.
Dravid and his team analyzed how different types of tea – black, white, oolong, green, rooibos, herbs, loose leaves and the traditional lipton – interact with lead in the water.
To do this, they let tea rest for different periods of time and then measured the amount of residual lead in the liquid.
The compounds of tea leaves, called catechins, act as “Tiny Velcro hooks” that catch the lead molecules, explained Michelle Francl, chemistry of the Bryn Mawr College and author of a book about tea chemistry. He also indicated that the structure of tea leaves, with “Ridges and valleys”provides the necessary surface for that interaction.
Although these properties have been known for a long time, Dravid and his colleagues were the first to examine the elimination capacity of lead in a single cup of tea. They discovered that black tea leaves, when wrinkling during the roasted process, have a greater capacity to absorb heavy metals.
“In green tea and black tea, practically equivalent amounts of absorbed metal were found”said Benjamin Shindel, co -author of the study and doctorate at the University of the Northwest.
On the other hand, white tea crosses a milder preparation process, which maintains its smooth leaves and with less capacity to extract heavy metals from water. Similarly, herbal infusions, such as chamomile, do not filter these metals well, probably because they do not contain tea leaves, but flowers or other plants.
Despite these differences, the researchers concluded that the most relevant factor is infusion time. “The rest time of tea is much more important,” Shindel said.
They discovered that letting a cup of black tea stand for five minutes can eliminate up to 15 % of lead in the water. Although this is useful, “it is not a safe level” of exposure to lead, according to the EPA.
“With lead and other pollutants, any decrease is significant to some extent, especially if you lack resources or infrastructure to filter these problematic materials,” said Caroline Harms, who participated in the research as a Dravid university student.
However, the greater the infusion time, the more bitter tea will be. Last year, Francl generated controversy by suggesting that adding salt to tea could mitigate his bitterness. “You can’t drink after 10 minutes of rest, and no amount of salt will remedy it,” he said.
In some samples of the study, tea was left at rest for 24 hours, which made it unbeatable.
The study authors pointed out that their objective was not to make public health recommendations, but to highlight a hidden benefit of a global habit.
They estimated that a country where the consumption of tea was high could reduce approximately 3 % the ingestion of lead from the water supply compared to another where tea was not drank.
“What a wonder!” Said Henrietta Lovell, founder of Rare Tea Co., a company that supplies tea to exclusive restaurants. Lovell stressed that in China tea has been used as a remedy for thousands of years. “The more I learn about tea, the more fabulous and fascinating it seems to me,” he said.
Francl considered that these findings could open the door to a scalable method to avoid heavy metal intake. “Since clean water is a global problem, if this proof of concept to produce drinking water, it would be very positive,” he said.