Q Are there benefits of drinking alkaline water?
A Despite the claims, there's no evidence that water marketed as alkaline is better for your health than tap water.
"It's all about marketing," said Dr Tanis Fenton, a registered dietitian and epidemiologist at Cumming School of Medicine at the University of Calgary. "There is no science to back it up."
The pH scale indicates whether a liquid is more acidic (lower pH) or alkaline (higher pH). Pure water has a neutral pH of 7, while tap water has some natural variation depending on its mineral content. Most bottled waters are slightly acidic, and sodas and juices are even more so.
Bottled waters sold as being alkaline typically claim to have a pH of 8 to 10. Some are from springs or artesian wells and are naturally alkaline because of dissolved minerals. Others are made with an ionising process, and water ionising machines are also marketed for home use.
Alkaline water companies make vague claims that it will "energise" and "detoxify" the body and lead to "superior hydration". And some claim that ionised water can prevent everything from headaches to cancer. But there is no evidence that drinking water with a higher pH can change the pH of your body, or even that this outcome would provide benefits.
Blood is tightly regulated at around pH 7.4, while the stomach, which secretes hydrochloric acid to digest proteins and kill food-borne pathogens, is acidic, with a pH of 1.5 to 3.5. If you drink water that is slightly alkaline, Dr Fenton said, the hydrochloric acid in the stomach neutralises it before it's absorbed into the blood.
Several small studies funded by companies that sell alkaline water suggest that it could improve hydration in athletes, but any potential benefits were modest, and an easier way to improve hydration is just to drink more water. And a 2016 review of research by Dr Fenton and a colleague found no evidence that alkaline water or an alkaline diet could treat or prevent cancer.
A study published last year found that adopting a plant-based diet and drinking alkaline water worked as well as medications to alleviate symptoms of laryngopharyngeal reflux, a severe form of acid reflux.
"I think that it can be a helpful tool for patients to help with their symptoms while they're transitioning to a more plant-based diet," said Dr Craig Zalvan, the study's lead author and a laryngologist at Phelps Hospital in Sleepy Hollow, New York. But he believes that most of the improvement in his patients comes from dietary changes. Once symptoms improve, he says, there is no need to keep drinking alkaline water.
There are also hints of potential risks from alkaline water. Rat pups given alkaline water showed impaired growth and damage to cardiac muscle. And a 2015 report said that when a municipal water plant in a town in Germany accidentally increased the water's pH to 12, skin burns ensued. While such a high pH is unlikely in bottled alkaline water, it's a reminder that a higher pH isn't necessarily better.
"The only health effects that we know of are danger signs, so for people to continue to market alkaline water - they're really as bad as the snake oil salesmen of yesteryear," Dr Fenton said.