You are, at your core, a microbial being,2 and while microorganisms are found everywhere from your skin to your mouth and even your blood,3 it's your large intestine where your body's largest bacterial ecosystem resides.4

If you treat it and the rest of your microbiome well, good health — both mental and physical — is likely to result. By nourishing this complex microbial community, you can even influence your gut-brain axis, which regulates digestion, mood, immune function and much more.5

The Number of Microbes Living in Your Gut Is Staggering

Your gut is home to bacteria, viruses, fungi, archaea and eukarya. The latter two resemble bacteria but are distinct groups of microorganisms. Bacteria, meanwhile, make up the vast majority of microbes in your microbiome. Three main phyla or groups of gut microbes make up the human microbiome and serve diverse structural, protective and metabolic functions:6

Bacteroidetes — Porphyromonas, Prevotella and Bacteroides

Firmicutes — Ruminococcus, Clostridium, Lactobacillus and Eubacteria

Actinobacteria — Bifidobacteria (the most prevalent type)

Broken down, the average person may host the following quantities of bacteria in different body regions.7 Remember that this is just an average — your age, health status, diet and environment all influence the numbers and diversity of microorganisms in your gut.8

Mouth — 100,000 colony-forming units (CFU) per milliliter (mL)

The digestion process begins in your mouth when you chew your food, making it easier to break down in your gut. Your mouth contains an impressive number of microbes to maintain oral health but if they become out of balance, disease may result.