Exposing kids to nasty germs might actually toughen them up to diseases as grown-ups, mounting research suggests.
A new study suggests that higher levels of exposure to common
everyday bacteria and microbes may play a helpful role in the
development of the body's inflammatory systems, which plays a crucial
role in the immune system's fight against infection.
"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," said
Thomas McDade, a professor of anthropology at Northwestern University
and lead author of the study.
The investigation focused on how various early childhood
environments affected levels of C-reactive protein (CRP), which rises in the
blood because of inflammation. C-reactive protein is also considered by
researchers to be a predictor of heart disease, independent of lipids,
cholesterol and blood pressure, though the association has been
disputed.
While earlier studies have been conducted in relatively affluent
settings such as the United States, the researchers were interested in
how C-reactive protein production differed in a country like the
Philippines, a population with a high level of infectious diseases in
early childhood, but low rates of obesity and cardiovascular
diseases when compared to Western countries.
The researchers used data collected from a study that began in the
early 1980s and tracked 3,327
Filipino mothers in the third trimester of pregnancy. The mothers were
interviewed about childcare behaviors, and their homes were assessed in
terms of hygiene (whether domestic animals roamed freely) and
socioeconomic resources. Researchers also followed up with the children
from such pregnancies every four or five years until the kids reached
their early 20s.
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, even though the
Filipinos suffered from many more infectious diseases as infants and
toddlers. CRP concentrations for Americans in their early 20s were on
average around 1 to 1.5 milligram per liter, while Filipino
participants in their early 20s had average CRP concentrations of 0.2
milligrams per liter — five to seven times lower than average CRP
levels for Americans.
"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 McDade. "In
the U.S we have this idea that we need to protect infants and children
from microbes and pathogens at all possible costs. But we may be
depriving developing immune networks of important environmental input
needed to guide their function throughout childhood and into adulthood."
The study will be published online on Dec. 9 in the journal Proceedings of the Royal Society B: Biological Sciences.