The gastrointestinal system contains more than 100 trillion microorganisms — a number that is 10 times larger than the number of cells in the rest of the human body.

They help us digest food, protect us from infection, enhance the immune system, help us to digest carbohydrates, regulate metabolic functions, and produce many different vitamins.

They also enhance the absorption of minerals such as iron and magnesium, and help prevent allergies — both from food and environmental sources.

In short, we can’t live without these organisms.

This vast array of microorganisms is referred to as the “gut microbiome.”

In medical school we were told that this microbiome is set at birth and does not change. But that simply isn’t true.

The microbiome can be affected by many factors, including what you eat, your stress level, and whether or not you are taking antibiotics.

What’s more, DNA sequencing has revealed that we each have our own unique bacterial microbiome.

In fact, recent research shows that the difference in gut bacteria may influence individual characteristics, such as whether a person is thin or fat.

How do you know what bacteria you have in your gut?

The most inexpensive method is to have a stool culture performed. There are special laboratories that are designed to culture stool samples and report the growth of the most common bacteria, yeast, and parasitic agents.

More detailed analysis can be done with DNA sequencing.