Parents shouldn't stop their kids from playing in the mud, for a new study suggests that early microbial exposures affect inflammatory processes related to diseases associated with aging in adulthood.
The research team from Northwestern University claims that exposure to infectious microbes early in life may actually protect individuals from cardiovascular diseases that can lead to death as an adult.
"Contrary to assumptions related to earlier studies, our research suggests that ultra-clean, ultra-hygienic environments early in life may contribute to higher levels of inflammation as an adult, which in turn increases risks for a wide range of diseases," said Thomas McDade, lead author of the study, associate professor of anthropology in Northwestern's Weinberg College of Arts and Sciences and a faculty fellow at the Institute for Policy Research.
Relatively speaking, humans only recently have lived in such hyper-hygienic environments, he added.
The study suggests that inflammatory systems may need a higher level of exposure to common everyday bacteria and microbes to guide their development.
"In other words, inflammatory networks may need the same type of microbial exposures early in life that have been part of the human environment for all of our evolutionary history to function optimally in adulthood," McDade said.
During the research, the team studied how environmental exposures early in life affect production of C-reactive protein (CRP) production in adulthood.
Levels of the protein rise in the blood due to inflammation, an integral part of the immune system's fight against infection. CRP research mostly has centered on the protein as a predictor of heart disease, independent of lipids, cholesterol and blood pressure, though researchers still dispute that association.
The researchers were interested in what CRP production looks like in the Philippines, a population with a high level of infectious diseases in early childhood compared to Western countries.
Blood tests showed that C-reactive protein was at least 80 percent lower for study participants in the Philippines when they reached young adulthood, relative to their American counterparts, though the Filipinos suffered from many more infectious diseases as infants and toddlers.
The study appears in the journal Proceedings of the Royal Society B: Biological Sciences.