Are we really 10% human and 90% microbe? Exploring the microbial world

Its often quoted that humans are 90% microbes and 10% human. In this podcast, Jonathan Eisen (Professor at the University of California) debunks this myth. It turns out that that these figures were pretty much made up. Better estimates are likely to be 50% human and 50% microbe. But that’s still incredible! And it's not just humans. Every plant and animal is covered in a cloud of invisible microbes!

Even more amazing is the diversity of these microbes in our body. There are 1000’s of different species of microbes in just one section of our body. And the species in different sections (e.g different parts of the gut) are usually very different from each other. 

"So while you might think of yourself as an individual human, you are really a walking ecosystem." - Jonathan Eisen

The ecosystem of bacteria in the human body is called the microbiome. And when you think of microbes or bacteria, you probably immediately think about gut health and probiotics (beneficial bacteria in a tablet). But research is revealing that the effects of microbes are a lot more dispersed. Your microbiome can affect your immune system, your brain function, your mood and make extra vitamins and minerals available from the food you eat.

While new technology has made microbes easier to study, a lot of people have oversold what we know. Probiotics are promoted as a remedy for everything from constipation to obesity. But many of the health claims are pure hype or massively inflated.

Research is still in its “early days” and there is a big distinction between what “we know” and what “we think we know.” -Jonathan Eisen

While there is some preliminary evidence that probiotics can be helpful in conditions such as irritable bowel syndrome (IBS), scientific evidence for most health conditions is simply not there.

There is a lot more that needs to be learned such as which probiotics are helpful, the dose required and who would likely benefit. And a generic probiotic is not suitable for everyone, because everyone has a unique microbiome with reasons for any imbalance different for every individual. Because of this, generic probiotics are often useless or may even do more harm than good. 

Despite the lack of scientific evidence, probiotics are booming. Its a US$60 billion industry which is growing rapidly. 

What really stands out for me is how little we know and the complexity of our biology and other natural systems. Despite this, we are quick to jump in and start messing around with these systems, looking for short cuts and magic bullets like probiotic tablets. Building on my argument in the food manifesto, we need to stop messing with these natural systems because simplistic interventions into a complex system can have unwanted consequences. 

Don’t get me wrong, I think a better understanding of microbes has massive potential and I'm excited about what we can learn from it. But I also think we need to be smart about this. We need to take an ecological approach that works sensitively with our microbial systems, not against them.

With this in mind, there are 3 areas of the microbial world which I’m exploring  and will be sharing with you in the future: 

  • The impact of food on the microbiome. Many studies (such as this one which compared to microbiome of BaAka hunter-gatherers and Bantu agriculturalists) support the idea that diet has the biggest influence on our microbiome. “We are what we eat” and our microbiome is giving us a new perspective on this.
  • Growing food with microbes - how do we grow food in a way that works with the microbial world. Studies have shown that plant microbes can improve plant growth, increase plant nutrition and make plants more stress and disease resistance. 
  • How gardening and dirt benefits your microbiome Your garden has its own microbiome, and research suggests it’s good for you. Humans have evolved for millions of years with a close connection with nature such as plants, animals and dirt. It's only recently that our modern lifestyle that has disconnected us with this ancient relationship.

If there are any other topics or questions that you want me to cover on microbes, let me know in the comments below.