A new study suggests that brewing tea may help remove heavy metals like lead from drinking water. (Image credit: Catherine Falls Advertising via Getty Images)
New research has shown that the process of brewing tea may be effective in removing toxic heavy metals, including lead, from drinking water.
A cup of tea has long been associated with a host of small health benefits, although previous research has focused largely on the effects of chemicals in tea leaves that are released during the brewing process.
Now, a new study has found that brewing can remove charged atoms (known as ions) of heavy metals in water, apparently by chemically bonding with them. This causes the heavy metals to stick to the tea leaves, pulling them out of the water. The study was published Monday (Feb. 24) in the journal ACS Food and Science Technology.
“We are not advocating that everyone use tea leaves as a water filter,” said co-author Vinayak Dravid, a professor of materials science at Northwestern University. “Our goal was to measure the ability of tea to adsorb heavy metals. Quantifying this effect highlights the untapped potential of tea consumption to passively reduce heavy metal exposure in populations around the world.”
More than 5 billion cups of tea are consumed daily, making it the second most popular beverage on the planet after water. Scientists have long studied the health effects of both green and black tea, linking the beverage to a reduced risk of cancer, stroke, and death from cardiovascular disease.
It’s unclear, however, why exactly a cup of English breakfast offers these benefits. Previous studies have linked the benefits to chemicals released by the plants, but the researchers in the new study suggest it may be due to the brewing process itself. (Heavy metals have been linked to increased risk of stroke and heart disease.)
To test their hypothesis, the scientists purchased several varieties of popular tea brands, such as Lipton and Infusion, including black, green, chamomile, oolong, white peony, and rooibos. (Chamomile and rooibos were brewed and consumed as tea, even though they belong to a different plant family than traditional teas.)
By brewing tea in the same way as ordinary people do, the researchers assessed the ability of tea to neutralize heavy metal ions in water at various concentrations, comparing them with water mixtures without tea.
The results showed that a typical cup of tea — one mug of water and one tea bag steeped for three to five minutes — can remove about 15 percent of lead from water at concentrations of up to 10 parts per million. While there is no safe level of lead in drinking water, the Environmental Protection Agency sets a limit of 15 parts per billion. Steeping also reduces other metal ions, such as chromium and cadmium.
Other trends were also noted. The type of tea bag significantly affected the results: cotton and nylon bags hardly adsorbed any contaminants, while cellulose bags removed most. In addition, the type of tea and the degree of grinding also played a role: finely ground black tea leaves showed the best results. They, along with green and white tea, significantly reduced the concentration of lead ions compared to oolong, rooibos and chamomile tea.
However, the most significant factor was steeping time. As expected, teas steeped the longest provided the best removal of contaminants.
“Any tea that steeps longer or has a larger surface area will effectively clean up more heavy metals,” first author Benjamin Schindel, a materials scientist at Northwestern University, said in a statement. “Some people steep their tea for seconds and won’t get much cleaning. But steeping the tea for a long time or even overnight — as is the case with iced tea —
Sourse: www.livescience.com
