Our bodies are confused by this 21st-century world.
IN the last half-century, the prevalence of autoimmune disease — disorders in which the immune system attacks healthy tissue in the body — has increased sharply in the developed world. An estimated one in 13 Americans has one of these often debilitating, generally lifelong conditions. Many, like Type 1 diabetes and celiac disease, are linked with specific gene variants of the immune system, suggesting a strong genetic component. But their prevalence has increased much faster — in two or three generations — than it’s likely the human gene pool has changed.
Many researchers are interested in how the human microbiome — the community of microbes that live mostly in the gut and are thought to calibrate our immune systems — may have contributed to the rise of these disorders. Perhaps society-wide shifts in these microbial communities, driven by changes in what we eat and in the quantity and type of microbes we’re exposed to in our daily lives, have increased our vulnerability.