LONDON, UNITED KINGDOM
- A high intake level of strong coffee may reduce the risk of heavy-metal poisoning in cities where drinking water contains high levels of these contaminants, reported New Scientist recently.
An international team of scientists has found that while coffee is filtering, the coffee grounds mop up as much as 90% of the copper and lead dissolved in the water.
Many cities in the developing world have high levels of toxic metals as soluble metal ions in their drinking water. Copper and lead enter the water as it runs through pipes and storage tanks or makes contact with lead solder.
Mike McLaughlin of CSIRO Land and Water in Adelaide wondered if ground coffee might remove heavy metals. Because dissolved heavy metal ions are positively charged, and coffee contains uncharged and negatively charged molecules, the metal ions might be taken out of solution by binding to negatively charged molecules in the coffee grounds.
To test this idea, McLaughlin and his colleagues used water spiked with different levels of copper and lead to brew coffee by the water-drip method. When they measured the concentrations of metal ions in the resulting coffee they found that between 78 - 90% of the copper and lead had been removed. "The deeper the bed of coffee in the drip-maker, the more effective the removal of heavy metals," says McLaughlin.
He adds that the process probably also removes other heavy metals such as mercury, cadmium and zinc, though this hasn't been tested. "It is also possible teabags and tea leaves may work in the same way," he suggests.
The findings could mean that the risk of lead and copper poisoning in cities where people drink a lot of coffee is lower than expected.