Bacteria and our relationship with them go back to the origins of life on this planet. Without them we would simply not be here today! The microbes that live in and on us outnumber our own cells by a staggering 10 to 1. It’s a perfect example of biological symbiosis, two organisms living in mutual harmony, well not always harmonious and when it does go awry then our health takes a nosedive.
Our genetics, the human genome has made a life-long partnership with the microorganisms that call us home, otherwise known as the microbiome. This partnership of genome and microbiome has navigated us through precipitous environmental changes, most recently the Ice Age. Could our genome have achieved this alone? No, absolutely not. Our microbiome serves as a first line of defence against environmental aggressors, pathogens, toxins and stressors. But, that’s not the only thing it does; it mediates our immune response, it provides essential molecules that our own host cells are unable to produce and it provides a small amount of energy in the form of short-chain fatty acids. Put simply, without our microbiome we would have perished long ago.
If we wish to improve our health we really need to understand the relationship between our genome and microbiome and learn how they combine to navigate a healthy path through a changing and challenging environment. One of the biggest physiological changes of human evolution over the past few million years has been the increase in the size of our brains.
The brain is our most metabolically active and demanding organ taking up to 25% of our daily energy and this rises to 70% in babies and young children. This explains why babies come packaged with so much body fat, they simply have to have a secure source of energy to fuel the rapid development of their brains. No other species in the animal kingdom is born with so much body fat. This hungry brain drove an appetite for energy-dense food, primarily fat from large animals. When we hunted these larger animals to extinction we needed to adapt to more fleet-footed prey which required higher cognitive function and hence an increase in brain size. It was this exquisite interplay between increasing energy demand and increasing food scarcity that fuelled the increase in brain size. This also led to a dependence on fat especially from animals and this in turn led to a decrease in the size of our large colon whilst also increasing the size of our small intestine so that we could extract the energy from food more quickly. Over time the energy contribution from the large colon decreased however its protective function was maintained.
It could be argued that many of today’s modern diseases arise from an imbalance or dysbiosis in the gut and this has come about by eating foods that disrupt the capacity of our bacterial communities to protect us. Agricultural foods such as wheat and dairy and industrial foods such as refined flour, sugar and oils have decimated the bacterial communities within our gut. We are not adapted to consume foods that arose with farming only 10,000 years ago and in evolutionary terms this is a mere blip. Therefore, if you avoid these foods your microbiome will repay you in better health and well being. Therefore, the bottom line on training your bacteria is to avoid feeding them foods they are not adapted to eat and stick to energy-dense nutrient-dense natural whole-foods.