Objective: To estimate the association of improved nutrition in early life with adult intellectual functioning, con- trolling for years of schooling.

Design: Prospective cohort study.

Setting: Four villages in Guatemala, as well as locations within Guatemala to which cohort members migrated.

Participants: Individuals who had participated as children in a nutrition supplementation intervention trial from March 1, 1969, through February 28, 1977 (N = 2392). From May 1, 2002, through April 30, 2004, adequate in- formation for analysis was obtained from 1448 of 2118 individuals (68.4%) not known to have died.

Interventions: Individuals exposed to atole (a protein- rich enhanced nutrition supplement) at birth through age 24 months were compared with those exposed to the supplement at other ages or to fresco, a sugar-sweet- ened beverage. We measured years of schooling by interview.

Main Outcome Measures: Scores on the Serie Inter- americana (InterAmerican Series) tests of reading comprehension and the Raven Progressive Matrices, obtained from May 1, 2002, through April 30, 2004.

Results: In models controlling for years of schooling and other predictors of intellectual functioning, exposure to atole at birth to age 24 months was associated with an increase of 3.46 points (95% confidence interval, −1.26 to 8.18) and 1.74 points (95% confidence interval, 0.53-

2.95) on the InterAmerican Series and Raven Progres- sive Matrices tests, respectively. There was no statistical interaction between exposure to atole at birth to age 24 months and years of schooling on either outcome (P = .24 and P = .60, respectively).

Conclusion: Improved early-life nutrition is associated with increased intellectual functioning in adulthood after taking into account the effect of schooling.