Copper vessels and health: what the research actually says

Tamra is the Sanskrit word for copper, and tamra jal is water kept in a copper vessel. The custom is to fill a copper lota or jug at night and drink from it in the morning.

The Sushruta Samhita, a classical Ayurvedic text, describes keeping water in vessels of silver, copper or clay to keep it pure. Researchers who study the practice cite its Sutra Sthana, chapter 45.

Ayurvedic writing goes further and treats copper water as a general tonic. That is a traditional belief. We found no clinical trial that tests it, so this article treats it as tradition, not evidence.

The best-known study was published in 2012 by a team from Bengaluru and Kolkata. They added six diarrhoea-causing bacteria, including Vibrio cholerae and Salmonella Typhi, to ordinary drinking water.

The water was kept in 2-litre copper pots at about 26 °C for 16 hours. No bacteria could then be grown from the copper pots, even after an extra enrichment step. In glass bottles, the same bacteria survived or multiplied.

An earlier study from Punjab found a similar pattern in brass. E. coli and coliform bacteria in water kept in a brass mutka could no longer be cultured after 48 hours. This held for water from rural households too.

Conditions matter. Later work showed that temperature and pH change how fast a copper vessel acts on E. coli. Proteins and other organic matter in the water slowed it down sharply, which is one reason to store only plain water.

On dry copper surfaces, bacteria die quickly. Scientists call this contact killing. A 2011 review by Grass, Rensing and Solioz measured the rate. Bacterial counts fell at least ten-millionfold (7 to 8 logs) per hour.

In February 2008 the US Environmental Protection Agency (EPA) registered copper alloys as antimicrobial touch surfaces. Their labels allow the claim that, cleaned regularly, they kill more than 99.9% of certain bacteria within two hours.

The same labels rule out direct food contact, and say copper supplements standard cleaning rather than replacing it. The registration covers door handles, rails and counters, not utensils or drinking water.

Hospital trials reviewed in 2011 found between 63% and more than 90% fewer bacteria on copper and brass fittings. Fewer germs on a surface is not the same as fewer infections in patients.

The water studies have limits too. They used a handful of bacterial strains, small vessels and controlled water in a laboratory. The 2012 authors could not rule out that some bacteria were alive but unable to grow, and called for tests in real homes.

Copper is an essential nutrient. The body uses it in several enzymes, including cytochrome-c oxidase and superoxide dismutase. Clinical copper deficiency is rare.

Most of it comes from food. WHO's background paper on copper puts adult intake from diet at 1 to 3 mg a day. Drinking water usually adds 0.1 to 1 mg.

Water from the copper pots in the 2012 study held 0.177 mg of copper per litre. That is less than a tenth of WHO's limit.

WHO's guideline for copper in drinking water is 2 mg per litre. It allows 2 to 3 litres of water a day, plus food and supplements, without upsetting the stomach.

In trials with volunteers, nausea became more common from about 4 mg per litre. Symptoms usually start 15 to 60 minutes after drinking, and nausea and vomiting are more common than diarrhoea. Above about 2.5 mg per litre, water tastes bitter.

Acid draws more copper out of the metal. In the 2012 team's earlier test, slightly acidic distilled water picked up about 420 micrograms of copper per litre. Ordinary tap water picked up 177.

That is why the US FDA Food Code bars copper and brass from contact with food below pH 6. Its examples are vinegar, fruit juice and wine. India's FSSAI treats copper or brass containers that are not properly tinned as unfit for preparing or storing food.

Some people need more care. Wilson disease is an inherited disorder in which copper builds up in the liver, brain and eyes. WHO also notes that some copper outbreaks affected children at lower levels than adults.

Our copper water bottle guide covers first use, cleaning, and why the inside turns dark. HV makes and supplies copper lotas, jugs, glasses and water bottles, and every piece in the catalogue carries its own code.

• Fill it with plain drinking water at room temperature, the condition the studies tested.
• Drink it within the next day, then empty, rinse and refill. Don't top up yesterday's water.
• Keep lemon water, juice, buttermilk, milk, tea and sweet or fizzy drinks out of bare copper.
• Keep hot drinks out too. The tests were run at room temperature, and the safety figures do not cover hot liquids.
• Cook in tinned (kalai) vessels, not bare copper or brass.
• Treat copper water as part of your daily water, not a dose. For infants, pregnancy, liver disease or Wilson disease, ask your doctor first.

Brass (pital) and kansa are both copper alloys. Brass is copper with zinc. Kansa is bell metal, a bronze of about three to four parts copper to one part tin.

Copper's effect on germs carries over to its alloys, but it depends on how much copper they hold. The 2011 review found that a higher copper content made contact killing more effective.

The EPA's 2008 registrations covered five alloy groups, with nominal copper content from 96.2% down to 66.5%. Hospital trials used brass tap handles and push plates of 60% to 70% copper.

For stored water, the Punjab brass mutka study is the main direct evidence. We found no published study of water stored in kansa, so any claim for kansa water rests on its copper content, not on tests.

The cautions carry over as well. The Food Code rule names copper alloys such as brass, and kansa is a copper alloy too. Keep sour food out of bare brass, and serve it in kansa rather than storing it there.

This article is general information, not medical advice.