By Andrew Stern

CHICAGO, July 7 (Reuters) - A nutritious diet in early childhood provides a developmental edge that may not be apparent until adulthood, according to a long-term study of Guatemalan villagers released on Monday.

For eight years beginning in 1969, a trial was conducted in four villages located in Guatemala's northeast Highlands where hundreds of villagers were provided a protein-rich, sweetened porridge while others received a sugary flavored beverage with no nutritional value.

Three decades later, many of the same children who were 2 years old or under then and are now adults were tested on their reading ability and nonverbal skills such as pattern recognition.

"The impact of being exposed to the better nutrition in the first two years of life had an impact on performance on these tests roughly equivalent to the impact that an additional year of schooling would have had," researcher Aryeh Stein of Emory University in Atlanta, said in a telephone interview.

Overall, the Guatemalans averaged four years of schooling but those who received the porridge attended an average half-year longer than those who got the sweetened drink.

Girls averaged about an extra year of schooling. The porridge-eaters were also taller by an average of 0.8 inches (2 cms).

A similar study published in February found the nutritious porridge given to Guatemalan boys aged 3 and younger paid dividends later, with their hourly earnings as adults 46 percent higher than those who did not get the protein diet.

The developmental advantages from the nutritious diet appeared to encourage those children's parents to send them to school for longer, Stein said. It also may have fostered in the young children more interaction with their environment and, later, more ability to absorb what school had to offer.

It was also possible that the added nutrition boosted physical development of their brains, but the researchers had no evidence of that.

At around the same time, there were at least three other similar trials going on in Colombia, Taiwan and among poor New York City residents that evaluated the benefits of nutrition and other interventions on child development.

"Our study like the others had very limited evidence of efficacy of impact from the nutrition in the short term," Stein said. "But now we're seeing it ... it just took longer to develop. You have to have the kids go through schools first to see the differences."

At the time, researchers debated whether it was ethical to give some villagers the protein supplement while depriving others. Today, an objection to such a study might be that the sugary drink could lead to obesity or other problems, Stein said.

(Editing by Maggie Fox and Alan Elsner)

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