Humans have about 100 trillion gut bacteria, or intestinal bacteria flora, living inside their digestive tracts. Astonishingly these tiny microorganismsoutnumber human cells by 10 to 1. The gut bacteria are responsible for digestion, production of essential nutrients and vitamins, protecting the intestines against harmful microbes and carcinogens, and stimulating the body’s natural immune system to fight against disease. In fact 70 percent of your immune system is related to gut health. The gut also produces all the same neurotransmitters as the brain. For this reason it is often called the second brain. This is intuitively understandable to anyone who has ever had GI distress before a stressful event, such as an exam, or had a strong “gut” feeling.
New research has shown that the bugs in your gut can affect your mood. A team in Ireland showed that mice fed probiotic broth rich in lactobacillus rhamnosus showed less anxiety – that is they were more willing to venture into wide open spaces or to walk across narrow walkways. They also produced less of the stress hormone cortisol in response to stressful events. Lactobacillus salivarus, however, showed no effect. Lactobacillus rhamnosus had no effect when the vagus nerve was severed which indicates that the parasympathetic nervous plays a major role in modulating the communication between the gut/brain axis.


Gut bacteria  alsoinfluence our weight. Bacterial  proteins called the toll like receptor (TLR5) act  like a traffic cop for controlling intestinal pathogens. Mice that lack this receptor eat 10 % more than control mice, and are about 15 % heavier. This may be due to the increased inflammation present from the pathogenic bacteria. The increased inflammation makes cells less sensitive to insulin which leads to all the symptoms of metabolic syndrome in the TLR5 deficient mice – weight gain, high cholesterol, high triglyceride levels and elevated blood pressure


Other recent research has found that we all have an identifying gut bacteria enterotype that is as distinctive as our bloodtype. Researchers examined the feces of Europeans, Asians and Americans and found that there were three distinct clusters of gut bacteria that were not related to age, sex, gender, nationality or diet. This means that our bugs in our gut may be as identifying as our bloodtype.


Since gut bacteria have been shown to relate to mood and weight, as well as to how we digest and absorb nutrients and medications, and also outnumber us by 10 to 1 , further research on enterotypes may provide new therapies for improving our health. In the meantime some ways to promote good gut health are to avoid excessive or trivial uses of antibiotics, to shun processed foods, to increase dietary fiber, to respect food sensitivities and to replenish gut bacteria through the use of probiotics.