Are we really more bacterial than human?

Let’s answer this important question…

Is it true that bacterial cells outnumber our human cells in the body?

As you know, science is constantly evolving, and we are learning more and more about the human body and how it functions.

And that includes all the cells which live in the human body!

In 1977, a paper was published which stated that there were about 10 trillion human cells in the human body… but about 100 trillion bacterial cells in the human body!

Which means that there were about 10 times more bacterial cells in the body that there were human cells.

That’s where the popular “10 to 1 ratio” comes from – i.e. 10 bacterial cells per each human cell.

And this was the accepted ratio for over 35 years!

But then in 2016, another scientific paper was published which also looked at the ratio of human cells to bacterial cells.

Because the technology had developed, they were able to get better estimates of the number of both bacterial and human cells in the human body.

What did they find?

Well, that there were actually closer to 39 trillion bacterial cells in the human body (instead of 100 trillion cells as previously thought).

And how many human cells are there in an adult?

About 37 trillion (more than believed back in 1977)!

Which means that the bacterial cells to human cells ratio in the body is closer to 1 to 1… rather than 10 to 1, like originally thought!

But here are another 2 important points:

1. A human cell is about 10 times larger than a bacterial cell. So, the total mass of bacterial cells is really only about 0.2kg or about 0.3% of the overall body weight.
2. Most of the bacterial cells reside in the colon, while the human cells are all throughout the human body.

Which means that, even though we have a larger number of bacterial cells than human cells in our bodies, we are still more human than bacterial.

And as technology advances, so will science… not just in the area of microbiomics, but in every area.

So stay tuned as we continue updating you on this!

And if you haven’t already, be sure to check out the Advanced Gut Restoration Nutritional Advisor certification here.

AUTHOR: Alex Ruani, Research Director

Updated on: 14/10/2026