Realising the importance of our microbiome: Best ideas of the century

“The gut microbiome has transformed our understanding of human health,” says Tim Spector at King’s College London, co-founder of the Zoe nutrition app. “We now know our microbes influence everything from metabolism and immunity to mental well-being.”

While this understanding has accelerated over the past 25 years, humans have long used microbes to influence health. While they didn’t realise what they were doing, the Romans used bacterial-derived remedies to “guard the stomach”, for instance.

In the 17^th century, microbiologist Antonie van Leeuwenhoek first described the parasite Giardia, from his own stool. Yet it took another two centuries for scientists to validate his findings, and until the 21st century to appreciate how deeply the microbes that line our guts and skin affect our well-being.

By the 1970s, researchers were making headway, realising that gut microbes could influence how drugs are broken down, altering their efficacy. Experiments with faecal transplants hinted at how microbial communities might restore health. But it was only in the 2000s, with rapid advances in genetic sequencing and computing, that the field was truly transformed. Early genome sequencing revealed that each person carries a unique microbial “fingerprint”, which includes viruses, fungi and archaea.

In the early 2000s, several landmark studies showed that our microbiome and immune system communicate directly. This symbiotic relationship reframed the microbiome as an active participant in our wellness, and it was soon found to influence numerous systems, from the pancreas to the brain.

Striking discoveries followed: faecal transplants could cure Clostridium difficile infections; microbes from mice with obesity could make lean mice gain weight; specific populations of bacteria could reverse autism-like symptoms in mice. More recently, there have even been signs that microbial dysfunction can trigger diabetes and Parkinson’s disease. “Recent discoveries about the human microbiome reveal its influence far beyond the gut,” says Lindsay Hall at the University of Birmingham, UK.

Today, researchers are getting a clearer picture of how microbial diversity underpins good health and how boosting it can help treat conditions like irritable bowel syndrome, depression and even some cancers. Studies are also exploring how to seed a healthy microbiome early in life, which Hall says could have “profound, lasting impacts on health”.

In just a few decades, the microbiome has gone from obscurity to being considered in all areas of medicine. Now, we enter a time where careful trials are needed to separate overhyped products from those that have the potential to reshape how we diagnose, prevent and treat disease.