Our brain, gut, immune, and hormonal systems are intricately interconnected—and recent research has brought many fascinating studies about how crucial our microflora is to our bodies. These microorganisms are now understood to be crucial to genetic expression, body weight, mental health, memory, and risk of diseases as varied as Crohn’s, IBD, obesity, to diabetes and cancer.
The human body functions largely due to the presence of microorganisms including bacteria, fungi, and viruses. It is estimated that approximately 90% of the cells in and on the human body are those of microorganisms, and only 10% are actually human cells. Though there are microorganisms living on virtually every surface of the body, there are a few areas of interest that are generally referred to when one speaks of the microbiome. These are:
- Gastrointestinal tract. This is the most commonly talked about area of the microbiome, largely to its diverse and vast population of microorganisms, and its wide-reaching effects on the body. According to the European Society of Neurogastroenterology and Motility, the gut microbiota includes tens of trillions of microorganisms, including over 1000 different species of bacteria, and can weigh up to 4.5 pounds. The gut microbiome aids the body in food digestion and nutrient absorption, and also plays an important part in immune functioning.
- Mouth. Like the gut, the mouth has a large population of microorganisms. According to a recent study published in the American Society for Microbiology, the mouth is estimated to house anywhere from 500-700 species of bacteria. The same study also reports that the mouth microbiome composition may also be responsible for oral infectious diseases (tooth decay, gum disease, etc.) as well as systemic diseases such as cardiovascular disease, stroke, preterm birth, diabetes, and pneumonia. [NOTE: hyperlink to all relevant condition centers]
- Skin. The skin is the body’s largest organ, accounting for approximately 15% of the average human’s body weight. The skin is host to a multitude of microorganisms that assist it in its many functions, including sweating, heat and fluid retention, and acting as an immune barrier. The constitution of the skin microbiome is largely dependent on the skin surface, the individual’s health, and the external conditions. Because of the variety of factors affecting the skin microbiome, these microorganismal populations tend to be extremely unique. A 2013 study published in Natural Reviews Microbiology found that an average of 68.1% of the bacteria found on a subject’s skin was only found on that particular subject.
- Vagina. The vagina is populated by trillions of microorganisms that change throughout a woman’s lifetime. Potential factors affecting vaginal microbiome include menstruation, sexual intercourse, douching, and pregnancy. According to the vaginal microbiome consortium, a healthy vaginal microbiome can help prevent sexually transmitted infections, urinary tract infections, and bacterial vaginosis as well as help promote healthy pregnancy.
There is still much ongoing research into the human microbiome; the full effect of the microbiome constitution on human health is not yet known.