The idea seems attractive enough: pure drinking water drawn from a sparkling stream and bottled without any extra chemicals or additives.

It's a pretty picture indeed — at least, right up until the beaver fever (or worse) hits.

A University of Alberta professor is acting as the proverbial wet blanket on the growing raw water trend, where companies collect water from natural areas, bottle it without treating or fluoridating it, and sell it for as much as $33 per litre.

"It's an insane idea," health professor Tim Caulfield said Tuesday on CBC's Radio Active. "I think every science-based health person is concerned about this idea."

Unfiltered water can transmit many illnesses and diseases, including diarrhea, cholera, dysentery, typhoid and polio. Beaver fever, or giardiasis, is a common cause of diarrhea among hikers or travellers who drink water that has not been properly filtered, treated or boiled.

According to the World Health Organization, 502,000 people die from diarrhea deaths each year, and more than 844 million people still lack access to a basic drinking water service — including many on First Nations reserves across Canada.

With the enormity of those statistics, Caulfield said the raw water trend is a real concern.

"It's almost obscene that this has become a fad," he said. "They are paying a lot of money for what's basically dirty water."

'This is dangerous'

Caulfield said the trend seemed to originate in California but has been spreading across North America.

He said the companies selling the water are riffing off some recent developments in science — for example, that some bacteria are good for you — and that the healthy bacteria and minerals are being removed in water treatment by the government.

The companies, he said, would use either scientific debates like the use of fluoride or major water contamination problems to add layers of legitimacy to their product.

Caulfield, a health law expert at the University of Alberta and a vocal critic of fad or celebrity-influenced health advice, is the author of Is Gwyneth Paltrow Wrong About Everything?: When Celebrity Culture and Science Clash.

He said companies are using these scientific developments to promote their own products, some of which have not even been approved by the U.S. Food and Drug Administration.

"This is right off the land, hasn't been treated — [and] that is part of the appeal," he said. "There really is no evidence to support it and it can be extremely harmful."

Caulfield acknowledged that there is some truth to the idea that some bacteria are good for you. "We do want to have a healthier relationship with germs," he said.

But, to be kind to both your gut and your wallet, "raw water" isn't the way to go.

"Bottom line, this is dangerous," Caulfield said.