The case for using gut bugs to cure diseases is strong, but transplanting gut microbes for diseases that there’s no proof it helps risks halting medicine’s march

(Image: Eye Of Science/Science Photo Library)

“THE average adult human is, in essence, a 10-meter-long tube.” So began a 2005 special issue of the journal Science dedicated to the gut and its microbial inhabitants.

At that time, it was becoming clear how influential those microbes are on our health and well-being. At first, the focus was on obesity and inflammatory bowel disease. But the list has since grown to include diabetes, cancer, immune disorders and even mental illness. It is getting hard to find health problems that aren’t in some way linked to gut microbes (see “Inside story on gut health: Why it’s time to take control“).

That is both good and bad news. Gut microbiomes are flexible and potentially open to manipulation. Understanding the interactions between them and our health would open up many therapeutic avenues.


But the complexity of the relationship makes disentangling it difficult. A decade ago, there was optimistic talk of using gut bugs to cure obesity. We’re still waiting.

There are dangers too. Faecal transplants are growing in popularity as a quick fix for an “unhealthy” microbiome. There is solid evidence that they work for a specific infection. But some are also recommending them for conditions when the evidence is thin or non-existent. As a New Scientist investigation reveals, a number of clinics are seeing unexpected side effects (see “Doctors call for faecal transplant regulation as concerns mount“).

It is easy to understand the appeal of faecal transplants. Yuck factor notwithstanding, they have an aura of naturalness and holism that many people find attractive. But that is no substitute for clinical trials.

The case for using gut bugs to cure diseases is as strong as it was in 2005, and conventional medicine is on the case (see “Smart probiotics: Wiring friendly bacteria to take out disease“). But the route from concept to clinic is long and hard. The US and Canada have taken the prudent step of regulating faecal transplants. The rest of the world should follow suit, lest the procedure becomes an unregulated cure-all that ends up squandering the great promise in that 10 metres of tubing.

This article appeared in print under the headline “Gut reactions”