These studies, along with epidemiological observations, seem to explain why immune system disorders like multiple sclerosis, Type 1 diabetes, inflammatory bowel disease, asthma and allergies have risen significantly in the United States and other developed countries.
Training the Immune System
“What a child is doing when he puts things in his mouth is allowing his immune response to explore his environment,” Mary Ruebush, a microbiology and immunology instructor, wrote in her new book, “Why Dirt Is Good” (Kaplan). “Not only does this allow for ‘practice’ of immune responses, which will be necessary for protection, but it also plays a critical role in teaching the immature immune response what is best ignored.”
One leading researcher, Dr. Joel V. Weinstock, the director of gastroenterology and hepatology at Tufts Medical Center in Boston, said in an interview that the immune system at birth “is like an unprogrammed computer. It needs instruction.”
He said that public health measures like cleaning up contaminated water and food have saved the lives of countless children, but they “also eliminated exposure to many organisms that are probably good for us.”
“Children raised in an ultraclean environment,” he added, “are not being exposed to organisms that help them develop appropriate immune regulatory circuits.”
Studies he has conducted with Dr. David Elliott, a gastroenterologist and immunologist at the University of Iowa, indicate that intestinal worms, which have been all but eliminated in developed countries, are “likely to be the biggest player” in regulating the immune system to respond appropriately, Dr. Elliott said in an interview. He added that bacterial and viral infections seem to influence the immune system in the same way, but not as forcefully.
Most worms are harmless, especially in well-nourished people, Dr. Weinstock said.
“There are very few diseases that people get from worms,” he said. “Humans have adapted to the presence of most of them.”