Tea leaves can escape lead, learning discovers

Tea leaves draw heavy metals out of the water, significantly reducing the amount of lead and other dangerous compounds that people may be drinking without their knowledge, a new study found.

Recent research highlights the potential uses of used tea leaves, from biofuels to gluten-free cookies. But new research shows the public health benefits from what countless people already do. According to one estimate, around 5 billion cups of tea are consumed every day around the world.

“You can see the meaning,” says Vinayak Dravid, a Northwest material scientist and author of the study published this week. “How often do you touch billions of people?”

In many countries, water used for sudden tea is contaminated with lead from aging pipes. According to the Environmental Protection Agency, nine million homes in the United States get water from lead-containing pipes. Lead is particularly dangerous for children. Exposure can lead to delayed development and behavioral problems.

Dr. Dravid and his team tested that different types of tea (black, white, oolong, green, rooibos, herbs, loose leaf, plain old lipton) were behavioured in the water with varying amounts of lead.

After that, tea was allowed to be steep for various periods. Scientists then measured the amount of lead remaining in the water.

A compound called catechins in tea leaves acts like a “little velcro” hook. The hook is latched into the latch, says Michelle Francl, chemist at Bryn Mawr College and author of the book The Chemistry of Tea. Dr. Frank also said that the “ridges and valleys” of tea leaves provided the surface area required for its interaction.

These properties were known for some time, but Dr. Dravid and his colleagues were the first to see the lead toxicity of a cup of tea. They discovered that the tea leaves become wrinkled after roasting and are therefore perfect for absorbing heavy metals.

“Green and black tea absorbed quite a similar amount of metal,” said Benjamin Sindel, another author who was a doctoral candidate for Northwestern while working on the research.

White tea, on the other hand, prepares a much more gentle. Its leaves remain smooth and have less surface area to pull heavy metal out of the water. Herbal tea lovers may be disappointed to learn that chamomile tea does a poor job in heavy metal filtering. Probably because it is made from chamomile flowers rather than tea leaves.

Yet these distinctions between different types of living rooms were not the most relevant factors. “How important is the time to brew tea?” said Dr. Sindel.

Researchers found that 5 minutes of soaking black tea can remove 15% of lead from the water, which is useful, but according to the EPA, there is no “safe level” of lead exposure.

“With lead and other contaminants, some reduction makes sense, especially when there is a lack of resources and infrastructure to repair some of these problematic materials,” said Caroline Harms, an undergraduate student at Northwestern Dr. Dravid, who is working on the research.

However, the longer the soaking time, the bitter the resulting tea becomes. Last year, Dr. Frank sparked a small international scandal by suggesting that adding salt to tea can reduce the bitterness. But even that controversial chemical hack has its limits. “After soaking for 10 minutes, it's really not drinkable and there's no amount of salt to help with it,” she said.

Some samples in this study must be soaked for 24 hours, which means no need for tea.

The authors of the study stated that they are less willing to prescribe public health for policymakers than to study the hidden benefits of global practices.

Researchers estimated that countries where people drink large amounts of tea are about 3% less lead from water supply than in the same country where people don't drink (virtual) tea.

“What a wonderful thing,” said Henrietta Lovell, founder of the rare Tea Company. Ravel, who supplies tea to exclusive restaurants, noted that it has been used in China for drug use for thousands of years. “The more you learn about tea, the more wonderful and attractive it becomes,” Laver said.

Dr. Frank believes the new findings can ultimately pave the way for scalable ways to prevent people from ingesting heavy metals. “Given that clean water is such a global problem, it would be pretty good if there was a way to take proof of this concept and tweak it to eventually produce drinking water.”