An example of a Google ad promoting natural products to fight cancer. (CBC)

Google needs to do a better job of filtering its advertisements and suggested links to avoid sending users to snake-oil-type sites, doctors say in a journal commentary.

In this week's issue of the British Medical Journal, Dr. Marco Masoni and colleagues at the University of Florence in Italy said they used Google Italia to search for the keyword "aloe" and found sponsored links to websites recommending aloe arborescens for the prevention and treatment of cancer.

Google's AdWords feature allows users to create advertisements, choose their own keywords and decide which Google queries their advertisements should match. The company then decides on which advertisements to show and in what order.

The authors argue that Google's automated matching to search terms sometimes presents inappropriate advertisements.

"Showing an advertisement that links aloe and cancer in response to a query with only the single keyword 'aloe' is inappropriate," the doctors wrote.

"Worse yet is when the website linked to has false medical claims. If improving the filter is too complex, it would be better simply not to display sponsored links in results of searches on medical terms or products."

Avoiding harm

Google's list of sponsored links to the aloe search led to a related link "Padre romano zago" that contained statements such as: "Cancer can be cured! Padre Romano Zago's cure, Aloe Arborescens, cured many people's cancer!" and other similar statements, the authors said.

To prevent possible harm to users, Google should improve its filters and algorithms, the article concluded.

A spokesperson for Google Canada said the company has strict terms and conditions about what ads are allowed.

"We do not allow ads for miracle cures, and online pharmacy websites have to be registered with the Royal Pharmaceutical Society of Great Britain," Wendy Rozeluk said in an email to CBC News.

"Our processes do a good job of rooting out such ads and preventing them from showing. If we discover that we are showing ads that break our terms and conditions, we will take them down immediately."

An editor's note accompanying the article said the journal's web site has carried advertisements through Google's AdWords service, but this was discontinued after complaints from readers about inappropriate matches between editorial content and advertisements.

Doctors as advisers

A related commentary by Joanne Shaw, chair of NHS Direct, argues that the internet has brought medical knowledge into the hands and homes of ordinary people, a move that should be welcomed and encouraged as good for patients and doctors.

The internet encourages people to respond quickly, which could improve survival and reduce complications from long-term conditions, Shaw said.

"The internet does not diminish the role of doctors but casts them as expert advisers rather than authoritarian figures with exclusive guardianship of special knowledge," she wrote.

"Many doctors already act according to those principles, and many patients will continue to want a more traditional style of relationship with their doctors. But people who look to the internet as a legitimate tool to help them with their health may already be in the majority, and this is something for us to celebrate."