If one of your resolutions for 2019 is to drink more water, or perhaps use less plastic, you might well be thinking about purchasing a reusable water bottle.
There’s an ever-expanding array of options to choose from and some labels and websites suggest their bottles come with a wide variety of health benefits.
Take copper water bottles, a pricey option which can now be found at farmers’ markets and fashionable online stores.
According to their sales pitches, storing drinking water in a copper vessel could improve your immune system, aid digestion, decrease wound healing times, and even boost your tan.
Other claimed health benefits of copper water bottles include improved joint health, iron absorption, thyroid health and better digestion.
So, is there any truth to these claims about copper water bottles?
Copper is indeed necessary for maintenance of many — if not all — of your bodily systems, including the immune and digestive systems.
It’s also involved in the production of the natural brown pigment, melanin: so there is a tenuous link between the metal and your skin tone.
But while copper might sound like a bit of a miracle metal and it’s clear your body does need it, deficiencies are extremely rare.
“It’s almost everywhere, it’s in most foods,” says Emeritus Professor Anthony Wedd, who has expertise in Menkes disease, a lethal genetic condition which affects the body’s internal regulation of copper.
“There’s no problem for people getting their copper from their diet because its main form is Cu2+, which is soluble in water: unlike iron, which can be tricky to get enough of.”
Toxicologist Professor Ian Musgrave can’t see any health benefits from copper water bottles.
“It just makes me weep,” he says.
“While copper can be beneficial, having it in your water bottle won’t do anything whatsoever: it’s nonsense.”
While copper is soluble in water, not many copper ions will leach out from a copper bottle into your water so long as your water is of a standard pH (that is, not too far from the neutral).
This means even if you did need to top up your supplies, a copper water bottle would not be a good source of copper.
Professor Musgrave says this also means drinking water out of copper won’t put you at risk from exposure to too much copper — which can also act as a poison at high enough doses.
Aside from mystical bodily benefits, could there be any other advantages to using copper water containers?
Certainly, in some situations, says Durham University’s Assistant Professor Karrera Djoko — also known as Twitter’s @thecopperdoctor.
“Copper does actually have very potent antibacterial properties.”
“Now in hospitals there are many successful trials where they replace touch surfaces — door handles, light switches — with copper or copper alloys,” she says.
“If bacteria come into contact with the surface they die really rapidly. It’s called contact killing.”
The earliest recorded medical use of copper is from around 4,500 years ago, where it was described as being used to sterilise wounds and drinking water.
“Before we had antibiotics — before we even knew what bacteria were — we already knew that copper had this ‘magical quality’ that stopped diseases,” says Assistant Professor Djoko.
“It was taken as copper salts. But they are highly toxic: if you drink a lot of them, it will destroy your kidneys and that’s partially why we don’t do that anymore. In terms of copper vessels though, that’s still very common even today.”
So could copper’s ‘contact killing’ capacity mean storing water in it actually be beneficial in terms of preventing bacterial contamination?
Copper vessels are used in some areas without access to clean running water, where drinking water needs to be stored for long periods of time. This reduces the possibility of the liquid being contaminated with bacteria.
But while there are some concerns about access to clean water in Australia, it’s not clear the average person is likely to benefit from using a copper water bottle.
“There is a level of bacteria that’s allowed in tap water in Australia — but it’s very low,” says microbiologist Professor Mary-Louise McLaws.
There are strict regulations on tap water across Australia and the vast majority of Australians do not need to worry about the safety of their water supply.
Despite this low and safe level of bacteria, Professor McLaws still recommends washing out your reusable water bottle — “with a bit of soap and elbow grease” — every day.
This is best hygiene practice — the same reason we should wash our hands each time we use the toilet.
It’s important to note that even trace bacteria can multiply and set up their own little happy sticky breeding colonies — known as a biofilm.
And, it’s not just tap water bacteria swimming around in your drink bottle, it’s all those juicy mouth bacteria too.
“Those germs in our mouth keep our teeth and the skin cells in the mucosa very healthy,” says Professor McLaws.
“But outside of our mouths, that bacteria can build up a film and spoil whatever you’re drinking — if you expose yourself to that bacteria, it probably won’t make you ill, though for hygiene purposes we need to be mindful.”
So, while a copper water vessel may be less prone to biofilm build up over time, it’s probably a good idea to wash out your water bottle each day — regardless of what it’s made out of.