Gaby
Tea has long been associated with health benefits. A new study from Northwestern University in the U.S. found that the brewing process helps remove ions of heavy metals from water. In other words, heavy metals stick to tea leaves, which pull them out of the water.
What Did the Scientists Discover?
Previous research tied tea’s benefits to plant compounds. But the authors of this study suggested the brewing process itself might play a role, as reported by Live Science. The researchers set out to test how brewing affects levels of toxic metals in water that are linked to stroke and cardiovascular disease risk.
For their experiments, the scientists bought several types of tea bags from popular brands, including black, green, chamomile, white, oolong, and rooibos (the plant used for rooibos is aspalathus). Chamomile and aspalathus are brewed and consumed like tea, but they come from different plant families than traditional tea.
While brewing these teas, the researchers tested how well the beverages removed heavy metal ions from water. They found that a standard cup brewed for three to five minutes could remove about 15 percent of lead from water containing up to 10 parts per million of lead. Although there is no safe level of lead in drinking water, experts have established an acceptable limit of 15 parts per billion. Brewing also reduced ions of other metals, including chromium and cadmium.
The type of tea bag mattered. Cotton and nylon bags didn’t help adsorb contaminants, while cellulose bags removed a larger share. The tea type and leaf grind also made a difference: finely ground black tea had the strongest effect, with green and white teas performing well too. Those three reduced lead ion concentrations more effectively than oolong, rooibos, and chamomile.
The Most Important Factor – Brewing Time
Brewing time turned out to be the biggest factor in removing toxic metals from water.
“Any tea that is brewed longer or has a larger surface area will effectively remove more heavy metals,” said materials scientist Benjamin Shindel, the study’s lead author. People who brew tea for just a few seconds shouldn’t expect significant purification. “But brewing tea for a longer time will extract a larger portion of the metal, or possibly even nearly all of the metal from the water,” he said.
“If people were to drink an additional cup of tea each day, we might eventually see a decrease in diseases closely linked to heavy metal exposure,” Shindel said. “This could also help explain why people who drink more tea have lower rates of heart disease and strokes compared with those who drink less.”
The study’s findings were published in the journal ACS Food and Science Technology.
Worldwide, people drink more than 5 billion cups of tea daily, making tea the planet’s second-most-consumed beverage after water. According to experts, Turkey has the highest tea consumption.
