Black. Strong.Two sugars and no heavy metals. No, there’s nothing quite like a good coffee for taking the lead and copper out of your drinking water. According to an international research group, filtered coffee is capable of removing from 78 to 90 per cent of dissolved heavy metals from tap water; providing coffee-consumers with a safer, healthier drink.
Toxic metals like copper and lead are unwanted additions to the average glass of tap water. The pollutants get into drinking water from storage tanks, copper pipes and solder. In areas with older water distribution systems the concentrations of such metals can be high. Both copper and lead have long-term toxic effects on humans, and lead is strongly linked to intellectual impairment, especially in infants and young children.
Latest research though shows that coffee grounds seem to have a remarkable ability to mop up the heavy metal atoms. Dr Mike McLaughlin of the Commonwealth Scientific and Industrial Research Organisation (CSIRO) became intrigued by the issue after attending a conference.
“We were at a seminar at the University of Delaware, and a Chilean scientist, Dr. Gustavo Lagos, was presenting a paper on the problem of heavy metal contamination of drinking water in Santiago,” Dr McLaughlin recounts. “I asked the question: how do people in Santiago actually drink the water? Because if, as I thought, they drank a lot of coffee, chances were the coffee would absorb a lot of the heavy metals.”
As a result of Dr McLaughlin’s question, several researchers decided to run an experiment to find out exactly how much heavy metal does survive the coffee-brewing process, and how much is trapped in the grounds.
Using three different commercial brands of coffee, they found, to their surprise, that normal filtered coffee removed 78-90 per cent of copper and lead from the water. The reason for this is that coffee grounds have either uncharged or negatively charged molecules in them. Dissolved heavy metals, on the other hand, are positively charged. As a result, the heavy metal ions bind strongly to the coffee. When contaminated water passes through the grounds it leaves the metals behind.
“The deeper the bed of coffee in the drip-maker, the more effective the removal of heavy metals. We consider that the main factor influencing the extent of metal removal is contact time.” Says McLaughlin.
He also speculates that it is highly likely the process also removes other heavy metals such as mercury, cadmium and zinc from drinking water – though this remains to be tested.
“It is also possible tea-bags and tea leaves may work in the same way, but not as well as coffee,” he muses.
The researchers say the results of their study are important for formulating reliable risk assessment models for drinking water standards which protect the health of the public. The findings could mean that daily human exposure to heavy metals in many cities round the world may have been overestimated, depending on the local coffee-drinking customs.
The researchers make no mention of whether decaf brings the same result.