You Are 10% Human
In June 2012, the NIH Human Microbiome Project published landmark results revealing the human body hosts 100 trillion microbes (bacteria, viruses, fungi)—outnumbering human cells 10 to 1. These microbial ecosystems in our gut, skin, mouth, and other sites aren’t just passengers; they influence digestion, immunity, mental health, weight, disease risk, and possibly behavior. Microbiome research transformed our understanding of what it means to be human.
The Gut-Brain Axis
Research revealed bidirectional communication between gut microbes and the brain via the vagus nerve, immune signaling, and neurotransmitter production (gut bacteria produce 90% of the body’s serotonin). Studies linked gut microbiome composition to depression, anxiety, autism spectrum disorders, and Parkinson’s disease. The “gut feeling” metaphor gained scientific legitimacy as researchers mapped how gut bacteria influence mood and cognition.
Medical Applications
Fecal microbiota transplants (FMT)—transferring healthy people’s gut bacteria into patients—cure recurrent C. difficile infections with 90%+ success rates. Clinical trials explore FMT for obesity, inflammatory bowel disease, and even psychiatric conditions. Probiotic supplements became a multi-billion dollar industry, though quality varies wildly and benefits remain debated for most applications.
Diet, Antibiotics & Modern Life
Western diets high in processed foods reduce microbiome diversity compared to traditional hunter-gatherer populations with 30-50% more bacterial species. Antibiotic overuse disrupts microbiomes for months/years, potentially increasing allergy, obesity, and autoimmune disease risks. The hygiene hypothesis suggests overly sterile modern environments deprive immune systems of microbial training, contributing to autoimmune diseases.
Sources:
- Human Microbiome Project: https://commonfund.nih.gov/hmp
- Nature overview: https://www.nature.com/articles/nature11234
- Gut-brain axis review: )31347-2