Cut Parasites, Get Smarter: UNM research finds strong link between diseases and intelligence

Monday, July 12, 2010

Cut Parasites, Get Smarter: UNM research finds strong link between diseases and intelligence
ALBUQUERQUE JOURNAL, N.M.
By OLIVIER UYTTEBROUCK

July 12--Christopher Eppig says most people understand intuitively that it is beneficial to provide people with clean, safe drinking water and protect kids in sub-Saharian Africa from malaria.

But beyond the obvious -- keeping people from getting sick -- Eppig and other researchers at the University of New Mexico say protecting kids from parasites and infectious diseases is the surest way of increasing human intelligence -- trumping wealth, education and other factors.

The study suggests that parasites and infectious illnesses common in poor nations can rob children of the calories they need for proper brain development, explaining regional differ- ences in intelligence.

The work ventures into ideas about human intelligence that some people consider offensive, Eppig said, making use of earlier research that found varying levels of intelligence among people in different nations and regions.

"We are asking people to swallow kind of a bitter pill with this research," Eppig said. "We are asking people to at least entertain the idea that people in different parts of the world do not all have the same average intelligence."

The study appeared June 30 in the online edition of Proceedings of the Royal Society, a British scientific journal.

Eppig, a doctoral candidate in biology, and the other researchers drew on earlier studies that measured average IQ in 113 countries and estimated those of 79 others.

The UNM researchers then compared those figures with World Health Organization data on 28 major diseases, which correlated closely to the IQ data -- areas with more disease had lower average IQ scores.

The researchers also looked at other factors raised by other researchers as possible explanations for regional differences in intelligence, including education, wealth, nutrition and climate. The study found that none of those factors correlated more closely with the IQ data than infectious disease and parasites.

Disease isn't the only factor in determining intelligence, Eppig said, "but we think it's the most important thing."

Disease and parasites compete ruthlessly for calories needed by a growing brain.

"The human brain is, by a significant margin, the most costly thing in our body, especially during early childhood," he said.

In newborns, the brain consumes 87 percent of the body's metabolic energ y. At age 10, the brain still consumes about a third the body's energy.

Those figures "suggested to me the pathway that mediates the relationship between intelligence and disease," Eppig said.

Parasites and illnesses sap energy in a variety of ways. Especially damaging are intestinal parasites and diarrheal illnesses that prevent kids from absorbing nutrients they need for their growing brains, he said.

"Worldwide, diarrheal disease is one of the top killers of children under 5, which is the same time they are most vulnerable to energy being drawn away from the brain," he said.