The human microbiome

What food should I eat?  What food is good for me? What food is good for my bacteria?  Now I have your attention. What do you mean by bacteria?  Who cares about feeding them?

Everybody (or every body) houses millions of bacteria. They live everywhere. In the gut, the mouth and on the skin.  They are generally non-pathogenic; existing harmlessly and symbiotically with their host.

You could use the term microbiome or microbiota to describe the bacteria that inhabit or live on humans. There are trillions of microbes in the average human microbiome and it accounts for 1 to 3% of total body mass.
 
How many microbes in the average human microbiome?

Estimates of the size of the human microbiome vary from 40 trillion microbial cells to 100 trillion cells. One estimate has the human microbiome as outnumbering human cells by  1.3 to 1. Other estimates have a figure of up to ten to one.  Nobody knows how many bacteria are commensal with you at the moment. It will vary in the one person continuously. Every time you defecate you lose more bacteria than human cells so the ratio of human cells to bacteria will change.
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What does the human microbiome consist of?  Largely hundreds of different bacteria. Also some fungi and viruses, though much less.  It is known that the human microbiome is highly variable both within a single subject and between different individuals.
The problem of elucidating the human microbiome is essentially identifying the members of a microbial community which includes bacteria, fungi, and viruses. This is done primarily using DNA-based studies. You can actually get that done by sending a few samples to the relevant place.  It has become possible within the last ten years.

Where does the microbiome come from? Within seconds of being born a new born baby has been colonized by intrepid explorer bacteria largely from the mother. These bacteria can divide every 40-60 minutes so if conditions are suitable they increase rapidly.
Microbiomes are crucial for health. They are essential for digestion, control the calories we absorb, provide vital enzymes and vitamins as well as keeping our immune system healthy.  If you get the wrong bacteria in your microbiome then the microbiome has also been linked to disease such as diabetes, rheumatoid arthritis, muscular dystrophy, muscular sclerosis, fibromyalgia and some cancers.  They play a role in obesity and some psychiatric disorders such as depression and bipolar disease. In fact the number of diseases that have been linked to microbiome is so large I can’t mention all of them. I will return to this subject.

Microbiome and diet.  Your microbiome influences and determines what happens to the food you eat.  They decide lots of things such as if the food you eat is stored as calories or not. The bacteria in your gut largely decide what is going to happen to the food you eat.  So the microbiome determines what happens to the food you eat. And the food you eat determines your microbiome.  The two are connected.

What microbiome is the healthiest and best one to have?

What diet leads to the best possible microbiome?

In coming posts I will attempt to look at some of the answers to these questions.