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The “microbiome” is a name scientists use to describe the microorganisms in or on us, including their vast amount of genetic material. We have about 22, 000 different genes in our DNA, while the bacteria within us contain over 8,000,000 genes.

In 2007, researchers from the human microbiome project estimated that there are about 100 trillion microorganisms in and on the body. Newer research has revised this number to about 30 to 40 trillion. That might sound a little scary until you realize that about 99% of these bacteria and “friendly” and extremely valuable for our proper health.

The numbers not only change, but also can be confusing. For example, the human microbiome project reported there are over 10,000 different types of microorganisms, but the vast majority of these are about 1000 different types of bacteria living in our lower gut. Our stomach, with its acidic climate, is not a popular neighborhood; neither is the small intestine, teeming with digestive enzymes.

Scientist now realize that the friendly bacteria act like an extra organ in the body, which is responsible for many aspects of mental and physical health. They refer to all the bacteria and other microorganisms living inside us as our microbiota. Why are these tiny organisms important? Bacteria can communicate with every part of our body, especially with our brain. Gut bacteria are essential to our physical and mental well-being, to the point of determining how happy or sad we are.

Gut research is not a passing health fad. The National Institutes of Health list hundreds of human clinical trials on different ways of altering the composition of our microbiome to alleviate a wide variety of diseases. The study of our microbiome represent some of the most promising directions for solving the most intractable mysteries of restoring and maintaining perfect health, from prevention of disease to life extension.



Turnbaugh, PJ et al., The human microbiome project: exploring the microbial part of ourselves in a changing world. Nature. 2007; 449(7164):804-810

I Contain Multitudes: The Microbes Within Us and a Grander View of Life by Ed Yong, Ecco, 2016