microbiome health

Understanding the factors that shape our microbiome may be key to understanding and treating many common health problems. (Credit: vrx123 / Fotolia)

Now, don’t panic, but more than half of your body is actually not human. This is the latest from scientists, who claim that human cells make up 43% of the body’s total cell count, with the rest being microscopic colonists. 

The potential benefits of figuring out the other half of ourselves – the microbiome – would rapidly transform our understanding of diseases from allergies to Parkinson’s. The latest news has even lead a few in the field to begin questioning what it means to be “human,” which has seen new innovative treatments as a result. 

“They are essential to your health,” explained Professor Ruth Ley, the director of the department of microbiome science at the Max Planck Institute, “your body isn’t just you.”

This new discovery contradicts what we thought we already knew about our bodies, originally we thought our cells were outnumbered 10 to one, reports BBC

Professor Rob Knight, from University of California San Diego, commented, “You’re more microbe than you are human. That’s been refined much closer to one-to-one, so the current estimate is you’re about 43% human if you’re counting up all the cells.”

What’s more, “we don’t have just one genome, the genes of our microbiome present essentially a second genome which augment the activity of our own,” said Professor Sarkis Mazmanian, a microbiologist from Caltech. “What makes us human is, in my opinion, the combination of our own DNA, plus the DNA of our gut microbes.”

As a result, science is quickly uncovering the role the microbiome plays in digestion, regulating the immune system, protecting against disease and manufacturing vital vitamins. 

Professor Knight, added, “We’re finding ways that these tiny creatures totally transform our health in ways we never imagined until recently.”

This is a completely new way of thinking about the microbial world, especially since in the past, our relationship with microbes has largely been a conflicted one. 

In the past, we have thrown antibiotics and vaccines against smallpox, Mycobacterium tuberculosis or MRSA. Although we have saved a lot of lives through doing so, some researchers are concerned that this could have done more bad than good, to our so-called “good bacteria.”

“We have over the past 50 years done a terrific job of eliminating infectious disease,” noted Professor Ley. “But we have seen an enormous and terrifying increase in autoimmune disease and in allergy. Where work on the microbiome comes in is seeing how changes in the microbiome, that happened as a result of the success we’ve had fighting pathogens, have now contributed to a whole new set of diseases that we have to deal with.” 

Aside from this, the microbiome is also being linked to diseases including inflammatory bowel disease, Parkinson’s, whether cancer drugs work and even depression and autism. 

Another interesting example is obesity. Family history and lifestyle choices, of course, play a role, but what does this mean for gut microbes? 

If you were to live off of a diet of burgers and chocolate, this would affect both your risk of obesity and the type of microbes that grow in your digestive tract. But the difficulty comes when you try to work out if it’s simply a bad mix of bacteria metabolising your food in a way that contributes to obesity. 

In a bid to get some answers, Professor Knight performed experiments on mice that were born in the most sanitised world imaginable, so their entire existence is completely free of microbes. 

“We were able to show that if you take lean and obese humans and take their faeces and transplant the bacteria into mice you can make the mouse thinner of fatter depending on whose microbiome it got,” he explained. 

Increasing obese with lean bacteria helped the mice lose weight. “This is pretty amazing right, but the question now is will this be translatable to humans,” he said. 

Such work is a huge step forward in the field, as well as hope that microbes could be a new form of medicine. This is otherwise known as using “bugs as drugs.”

To learn more listen to The Second Genome on BBC Radio 4, repeated 21:00 BST Monday, April 16 and on the BBC iPlayer.