Throughout the past couple of centuries, many parts of the world have seen a drastic increase in sanitation. Developed countries have seen a decrease in the prevalence of disease and an increase in average lifespan, due at least in part to medical advances such as the development of antibiotics and antibacterial medicine, widespread access to clean running water, and efforts to educate people on cleanliness. However, recent studies are showing that this type of hyper-sanitation may actually be unhealthy.
A correlation has been discovered in both developed and developing countries between increases in sanitation and the prevalence of serious auto-immune problems, such as type one diabetes. Countries with advanced sewer systems, better access to medicine, and widespread hygiene programs have actually seen a much sharper increase in the incidence of illnesses of this type in the past half century than less developed countries. The key to understanding this trend may lie in our evolutionary history, and in both the good and bad bacteria that live inside of us.
One possible reason that autoimmune diseases are less prevalent in less-developed countries is because, as infants and children, the people of these countries are exposed to more bacteria and challenges to their immune system than in more-developed countries. Their bodies build up better immunity to pathogens while they are still young. If breastfeeding, they also are protected by the antibodies they receive from their mothers’ milk and these diseases do far less damage to them than they would if they weren’t exposed to them until they were adults. Chicken pox and polio are just two common examples of this type of disease. Another possible reason for the decrease in autoimmune disease in developing countries is that having a more challenged immune system early in life changes how people respond to infections later in life. And yet another possible explanation is that different microbiomes respond differently to the same virus.
Why are our bodies like this? For millions of years, as we evolved into humans, we were forced to live in harsh and unsanitary conditions. Our bodies became used to frequent contact with pathogens and have an expectation of being challenged. Ultimately, it seems, allowing our bodies to process diseases naturally and “educating” our internal biome of microorganisms is the more healthy thing to do.