Bacteria and yeasts (and other tiny creatures called archaea) densely populate our entire planet. They also densely populate human beings–to an extent that may surprise you. Different types of microbes live on our skin and in our digestive systems and other organs. The number of bacteria in a 155-pound human being is somewhere around 40 trillion. Compare that to the estimated number of cells of all types in the human body, which is rough 30 trillion.
Microbes have been with us for millions of year. New babies inherit a starter pack at birth, some of which have been passed down for many generations. These long-inherited families of microbes are part of what makes us human beings.
Healthy infants, children and adults have acquire microbe populations that are friendly to human existence. These bacteria populations play essential roles in digesting food to extract or create nutrients, converting food to energy, protecting us against diseases, and repairing external and internal damage. Our bodies could not function without these microbes.
We’re also exposed to different microbes through our interactions with food, the environment and our contact with people. Unlike with genres, our mix of microbes can change from time to time. In fact, you can change the mix in your body and on your skin within days just by altering what you eat. Antibiotics and other drugs, meanwhile, can shift the balance internally by killing or weakening friendly microbes along with unfriendly bugs. As a result, the differences in microbe populations from person to person can be dramatic–both in overall number and types.
People long have noted that there were connections between certain microbe populations and human health, but studying these connections has not been easy.
Fortunately, scientist now know much more about the microbes on our skin and throughout our bodies thanks to a powerful new tool: the Human Microbiome Project. One of the early findings of this research was a confirmation that human health and longevity is linked not only to our genes and the environment but also to the health and capabilities of those trillions of microbes. Some microbes are more beneficial than others, and some populations are damaging to our health. A healthy, friendly microbial population tends to fight off unfriendly microbes, or at least keep their populations at levels low enough to prevent significant damage. But if too many dangerous microbes reside in or on your body, they can make you ill.
Microbes have short lives (hours or days), so the colony renews itself rapidly using the food we share with them. This means we must constantly provide our digestive system with foods that nurture our internal microbiome. We need to encourage the beneficial bacteria and discourage the bad flora.
This is where the brain comes into play. Your brain and your stomach communicate in sophisticated ways. There are neural cells in your digestive system that are in constant conversation with neural cells in your brain. There are about as many neurons managing your digestive system as there are in the brain of a small dog. In the same way that dogs can be trained, so can your stomach-brain connection–if you persist gently but firmly.
The chemicals that our gut microbes produce can use this communications channel to trigger signals to the brain. These signals can influence our mental processes. Thus, what we eat and drink can affect our mood and behavior. Conversely, our changing moods can give us indigestion, create an urge to eat or suppress our appetite. When you suddenly feel like eating something unhealthy, is it your brain sending you this message, or some not-so-friendly sugar-loving internal bacteria?
Microbes have their own genes–and their environment is us, their human hosts. The vigor, healthiness and variety of these microbes can affect our well-being and longevity.