Researchers from Northwestern University (USA) tested different types of tea - green tea, black tea , oolong tea, white tea, chamomile tea and red tea - under normal brewing conditions with water containing trace amounts of lead and other metals including chromium, copper, zinc and cadmium.
A cup of tea can remove 15% of lead from drinking water.
Photo: AI
Exposure to lead can lead to chronic health problems, with high doses causing brain and kidney damage in the most severe cases.
After brewing the tea at 85 degrees Celsius, they assessed the amount of metal absorbed at different time intervals.
Results showed that tea can act as a filter to remove potentially harmful heavy metals such as lead from water.
Specifically, a regular cup of tea can remove 15% of lead from drinking water, according to Euronews.
Tea leaves have a high active surface area, which is a useful property for adsorbents and helps them release flavor chemicals into water quickly, said study lead author Benjamin Shindel, a professor at Northwestern University.
The process of transforming tea leaves enhances their ability to bind to certain substances, which black tea is more effective at than other types of tea.
Grinding the tea leaves also appears to amplify this effect by expanding the overall surface area available to capture metals.
Black tea is more effective than other teas
Illustration: AI
Brewing time and tea bags are also factors.
According to the results, longer tea brewing time resulted in greater reduction of lead.
Steeping tea for longer or using tea with a larger surface area would be effective in removing more heavy metals, says researcher Shindel.
Brewing tea for longer periods of time, or even overnight, will recover most or almost all of the metals in the water.
Researchers also observed that tea bags were also a contributing factor to this process.
Cellulose bags, made from wood pulp, are the most effective at retaining metal ions.
While cotton and nylon bags do little to remove heavy metals from water, Shindel said.
Plastic tea bags are already problematic because they release microplastics, but most tea bags used today are made from natural materials, like cellulose. These bags can release microscopic cellulose particles, but that is a fiber that our bodies can process.
If people drank an extra cup of tea a day , it's possible that over time we would see a reduction in diseases linked to heavy metal exposure, Shindeli said, according to Euronews.
Source: https://thanhnien.vn/phat-hien-them-tin-vui-bat-ngo-cho-nguoi-thich-uong-tra-185250317164310515.htm
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