Patients with debilitating diseases such as multiple sclerosis and Parkinson’s risk being exploited by websites offering expensive stem-cell treatments, scientists said yesterday.

An investigation of 19 companies that promote such therapies has found that most make inflated and overoptimistic claims about benefits that are not backed by evidence, while making little or no mention of the risks.

The findings, from a team at the University of Alberta, Canada, have prompted the International Society for Stem Cell Research (ISSCR), a leading professional group, to advise patients and their families to approach stem-cell therapy with extreme caution.

While both adult and embryonic stem cells have great potential for treating disease, very few uses have yet been proved to be effective and they should generally be offered only in properly monitored clinical trials, the society said.

In guidelines issued yesterday, ISSCR said: “The general public may not fully understand how many years of pre-clinical and clinical research will be needed to bring novel stem-cell-based therapies to fruition. Unfortunately, there are some clinics around the world already exploiting patients’ hopes by purporting to offer effective stem-cell therapies for seriously ill patients, typically for large sums of money, but without credible scientific rationale, transparency, oversight or patient protections.”

George Daley, of Children’s Hospital Boston, who contributed to the ISSCR guidelines, said: “I think these websites are dangerous. They overpromise effectiveness and safety of the therapy and underinform about risks. Overhyped marketing direct to patients is putting patients at risk of financial exploitation at the very least, and physical danger at the worst.”

Stem-cell therapies are tightly controlled in Britain, most of the Continent and North America, and only a few are approved for clinical use, chiefly for leukaemia, blood disorders and burns. Companies based in countries such as China, Mexico and Russia, however, often promote them as treatments for other conditions, such as MS, stroke, spinal cord injury, Parkinson’s and Alzheimer’s.

The Alberta study, published in the journal Cell Stem Cell, analysed 19 of these websites, and found that all claimed that stem cells could deliver improvements in patient conditions.

It found limited evidence for a possible benefit for only one of the disorders advertised — recovery after heart attack — yet every website but one mentioned other disorders as well. There was no evidence at all of benefits for Alzheimer’s or Parkinson’s, and only inconclusive evidence for MS. “These findings might suggest that providers are making inaccurate claims,” the scientists said. “Patients should be wary of claims made by stem-cell clinics on the internet. The direct-to-consumer portrayal of stem-cell medicine is overoptimistic given the peer-review literature.”

ISSCR urged countries that lack a regulatory system for stem-cell medicine to develop one, and offered its assistance with setting standards. It is also launching a handbook for patients to help them to assess claims.

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