91av

The microbes that live inside you hint more than your genes do about your likelihood of having health conditions ranging from asthma to cancer and schizophrenia, according to a new analysis.

The finding suggests that monitoring the ecosystems of bacteria, viruses, protozoa and fungi that live inside us could help diagnose or even prevent some conditions. “That’s going to change medicine,” says Braden Tierney at Harvard Medical School, who worked on the analysis.

However, it also raises privacy issues, because information about this microbiome is currently less tightly regulated than genomic data. “If our results are true, that microbiome data – which is not private – could be telling you a lot more about an individual than even their genetic data,” says Alex Kostic at the Joslin Diabetes Center in Boston, who also worked on the study. “We need to rethink data privacy in the age of the microbiome.”

Tierney, Kostic and their colleagues analysed 70 previous studies that had linked complex conditions to genetic variants or to various aspects of the microbiome, such as the microbe species present. They focused on conditions that may be influenced by both genetic and environmental factors, including schizophrenia, Parkinson’s disease, high blood pressure, asthma and obesity.

For 12 out of the 13 conditions that the team looked at, the microbiome was a better indicator than genetics of whether a person was likely to have a condition. The exception was type 1 diabetes (bioRxiv, ).

This is the first study to demonstrate that the microbiome is a good indicator of conditions that may be shaped by our environments. This makes sense, because the balance of organisms in our microbiomes is influenced by a range of factors, including our age, diet, exercise regimes and the medications we take.

“At first, I was very surprised,” says Kostic. “But now it’s like duh, of course it’s stronger. The microbiome is constantly changing, the genome isn’t.”

The findings show the need for a holistic approach to predicting health that takes both the genome and the microbiome into account, says Harriet Schellekens at University College Cork, Ireland. “You can’t look at one over the other in isolation.”

In most cases, alterations to a person’s microbiome are likely to be caused by changes in their health or lifestyle. But in some cases, an altered microbiome may be directly involved in causing a condition.

Three types of bacteria have been implicated in causing colon cancer, for example. In cases where microbes are to blame, treating the microbiome may prevent certain conditions developing. “That’s really the dream,” says Tierney.

But much more research is needed. We don’t know yet which features of the microbiome are most informative. This could include which microbes are present and how abundant each of them are, or which genes they have. Long-term studies are also needed to reveal how microbiomes change over time.

Microbiome studies typically involve just hundreds of people. We need to study hundreds of thousands of people to get better results, says the team.

Studies may now also need to take participants’ privacy more seriously. There is a potential exposure of privacy in ways people might not expect, says Tierney.

Currently, in the US, anyone can sign into the National Center for Biotechnology Information and download stored microbiome data that has been collected for research.

There is probably little reason to be concerned about privacy for now, says Matt Jackson at the University of Oxford. “It would be a lot of work to have a vague guess at someone’s chances of having a disease.”

But it could become a concern as more studies are done and the predictive power of the microbiome grows, says Jackson. What’s more, he points out that stool samples always contain human cells that are sequenced along with the microbes. This means that the raw data from microbiome studies contains human genome sequences that could in theory be used to identify individuals. It is regarded as best practice to remove these human sequences from shared data, but this isn’t always done.

In principle, microbiome data that is identifiable should be regarded as personal data under the European Union’s data protection laws and subject to the same restrictions, says Alison Hall at the PHG Foundation, a genomics think tank. “The test would be whether the microbiome data can uniquely identify a person.”