There are few things as comforting as sipping a warm cup of tea after a long day. For centuries, tea has been celebrated for its medicinal properties as well as feel-good appeal. A new study gives tea lovers another reason to enjoy their favourite beverage as it has been found to remove heavy metals like lead and cadmium from water.
Researchers from Northwestern University in the US have discovered that tea can naturally filter out heavy metals from water, reducing the concentration of harmful ions like lead, chromium, and cadmium.
This relatively lesser-known property of subtly cleansing water is likely to enhance the beverage’s popularity and elevate its status in the world of health drinks.
The new study published in ACS Food Science & Technology journal, looks at tea beyond its stress-busting and antioxidant properties. It provides a scientific explanation how having tea could help remove metals from the water by about 15%, which is a small effect but not an insignificant one.
The scientists in the study found tea could remove charged atoms, or ions, of heavy metals from water, apparently by chemically bonding to them.
What a cup of black tea could do to lead ions
Benjamin Shindel, the first author of the research, said that the team found a cup of black tea brewed for five minutes reduced the concentration of lead ions in water by about 15%.
Shindel said that even in a country like the UK, where lead levels in drinking water are not very high, having tea could have a small effect.
“It’s possible that on the margins, tea consumption is reducing [people’s] metal intake by a very small amount, and perhaps over the population of the UK, that’s reducing diseases associated with metal consumption by another commensurately very small amount,” he said.
The benefits of having tea have been well established by earlier studies; they range from lowering risk of stroke, dementia and even death.
How the experiment was carried out
The team of researchers in the study detailed their experiments on the cup of tea. They wrote how they brewed tea with different batches of water containing known concentrations of heavy metal ions. They then assessed the levels of these metal ions after different periods of steeping, and compared them to solutions without tea.
They discovered the brew reduced the concentration of all the metal ions including lead, chromium and cadmium.
As for lead, they found the longer brewing times and higher temperatures of water were linked to a greater reduction in the concentration of lead ions. They also discovered that ground tea had a greater effect than whole leaves.
Among different varieties, black, green and white teas reduced the concentration of lead ions in the water to a greater degree than camomile, rooibos and oolong teas when they were left to steep for 24 hours.
For bagged tea, the material made a difference — empty cellulose bags helped reduce lead ion concentrations, while empty cotton and nylon bags had no such effect.
While having tea would not reduce your exposure to heavy metals to a great extent, it would certainly make some difference.
The study is also likely to offer innovative solutions in removing contaminants from water.
