One of the greatest triumphs of medicine has been the successful treatment of many bacterial infections with antibiotics. Innumerable lives have been saved, but as usual, there is a but. We are familiar with the major “but,” namely the development of bacterial resistance to antibiotics and the worry that we are losing the war against the bugs. But there is another but. And that is the concern that antibiotic use may be interfering in a subtle way with the populations of the bacteria that normally inhabit our body. We share our body with bacteria. Lots of them. They live in our mouth, on our skin and mostly in our digestive tract. There are up to a thousand different varieties and their total number, some 100 trillion, is ten times greater than the total number of human cells in the body. Luckily bacterial cells are much smaller than human cells, their total weight is only about three pounds, so we don’t look like bacteria.
We have known since the groundbreaking work of Louis Pasteur and Robert Koch that bacteria can cause disease. Koch’s elegant experiment demonstrating that bacteria cultured from a tuberculosis patient were capable of causing the disease in a mouse cemented the bacterial theory of disease and launched the quest for antibiotics. Nobody back then was concerned about disrupting the body’s natural bacterial flora with antibiotics, the prime goal was to treat bacterial diseases. Now we know that the bacteria that inhabit our body are not just bystanders watching our internal activities, they are an integral part of those activities.
Who could have ever guessed that whether a baby is delivered vaginally or via C-section can have an effect on weight decades later? Yet that appears to be the case. A review of fifteen studies that examined over 160,000 births revealed that babies born by Caesarian section were 26% more likely to be overweight and 22% more likely to be obese as adults. The theory is that babies born by C-section pick up bacteria from the mother’s skin instead of her vaginal tract and that this bacterial population is more efficient at extracting calories from food. That notion is backed by the well-known increase in weight by farm animals treated with antibiotics. The drugs eliminate the bacteria that are less efficient in breaking down food into absorbable components. It is not only weight that may be affected by bacteria. Some researchers link Crohn’s disease, celiac disease, arthritis and even autism to a disturbance of bacterial population in the gut, possibly by antibiotics. The average North American child has three courses of antibiotics in the first two years of life which may cause a permanent shift in the body’s microbial environment. Exactly how bacteria affect health is not clear but the bacteria’s own digestive process produces a variety of metabolites that enter the bloodstream and may have an effect on the biochemistry that underlines everything from the control of blood sugar to the control of mood. We may think we are in control of our body but it seems that it is bacteria that rule!