INCAP Longitudinal Study: 50 Years of History and Legacy

This special supplement of the Food and Nutrition Bulletin summarizes the most outstanding results of the INCAP Longitudinal Study. The unique cohort of this study is the longest followed since birth in a developing country. It is made up of people who, from conception or before they turned 7 years of age, participated as beneficiaries of a nutritional supplementation intervention during the period from 1969 to 1977 and who in the last follow-up (2015-2017) were men and women aged between 42 and 57 years. This is an intervention in that participants or their mothers when they were younger than 6 months of age, of 2 pairs of villages of the Department of El Progreso in Guatemala, were provided on demand 1 of 2 types of supplement: (1) an energy and protein-rich gruel called “atole” or (2) a low-calorie and nonprotein drink called “fresco.” Both supplements contained the same amount of micronutrients. In addition to the nutritional intervention, a health education program and primary health-care assistance were provided, particularly aimed to mothers and young children.

To date, this study has had 7 important follow-ups over 50 years. The rigor with which the INCAP Longitudinal Study was implemented has generated strong and consistent evidence to support the need to invest in nutrition, health, and child care during the first 1000 days of life (from conception to 2 years) to achieve better childhood development, well-being, and human capital later in life. In addition, we are sure that there will be more follow-ups in the future, which will continue to provide invaluable knowledge to understand, prevent, and treat the most prevalent nutritional problems globally and their consequences on health, and even for the resolution of emerging nutritional problems.

We have brought together a group of 12 worldwide prestigious researchers, who have contributed to the INCAP Longitudinal Study over several years, to prepare this commemorative supplement. In addition, 5 researchers in training who participated in the latest study follow-up (articles 4 and 7 in this supplement) and 2 researchers from the World Bank (last article in this supplement) were appointed, the later 2 to have an external perspective on the contribution of this longitudinal study to public health and nutrition globally. The authors of each article of this supplement have pointed out the main evidence with which the INCAP Longitudinal Study has contributed to the advancement of knowledge about nutrition and its effects on human capital and development.

Many are the contributions that the INCAP Longitudinal Study has made to enhance the understanding of the effect of improving nutrition in the window of opportunity of the first 1000 days of life in physical growth, motor and mental development, well-being, and productivity, both inter and transgenerational, generalizable to many populations worldwide. The articles of this supplement review specific contributions of the study throughout the life cycle. Worth noting are the positive effects of “atole” during the first 1000 days in the reduction of morbidity and improving physical growth in this period, as detailed by Reynaldo Martorell. ¹ Haas and Rivera Dommarco ² then go on the positive longer term effects of the “atole” supplementation in early life in anthropometry, skeletal maturation, physical work capacity, and intellectual development. In addition, DiGirolamo and colleagues ³ describe how nutritional supplementation during the first 1000 days of life was associated with improvements in motor development and cognitive function during childhood and adolescence. Behrman and colleagues ⁴ further discuss the positive effects of the “atole” intervention on prime-age adult cognitive skills and productivities, including potential mechanisms of action. They also discuss the impacts of early-life exposure to “atole” on children’s height when starting school, on grades of schooling attainment, and on the extent of experience with higher skilled jobs, as well as the impacts of improved cognitive skills on wages.

Usha Ramakrishnan ⁵ shows the intergenerational effects of improving nutrition in early life on birth size, growth, body composition, and well-being of the next generation. In their review, Fernanda Kroker-Lobos and colleagues ⁶ reveal that exposure to improved nutrition in early life reduced the risk of diabetes by near 50% but increased the risk of overweight and obesity. Future research is warranted to understand the underlying mechanisms that drive these opposite associations. Paul Melgar and colleagues ⁷ provide a systematically compiled overview of the context in which study participants were born and raised and where most of them still live as adults. In addition, they contextualize the changes in health and nutrition for the study population over 50 years. The final contribution, by Meera Shekar and Lisa Saldanha ⁸ address perhaps the most pressing question of all: How the INCAP Longitudinal Study has contributed to invest in early life? This article highlights how the evidence generated by this study has contributed to a consensus in the international community that the first 1000 days of life are a critical “window of opportunity” for nutrition interventions, with long-term impacts on human capital.

Having a supplement that presents the most robust and up-to-date scientific evidence in the field of early nutrition and its consequences in adult life, will allow for more effective advocacy for the decision-making of authorities responsible for formulating health and nutrition policies and budgeting resources necessary to ensure them, particularly in Latin America. Furthermore, to reach a wider audience including researchers, teachers, students, technicians, and authorities from the government, and civil society and private sectors, the findings of the INCAP Longitudinal Study have been published in Spanish ⁹ and English. On previous occasions, efforts have been made to summarize the most outstanding results generated from the INCAP Longitudinal Study in high-impact scientific journals in English. This time, this information has been updated with the most recent findings, and summarized for a wider international readership that is unlikely to have followed the research in the original publications.

This supplement reaffirms our commitment to ensure the continuity of the INCAP Longitudinal Study. We are currently making efforts to raise new research questions and form new groups of researchers to respond to the challenges we face from the current economic, epidemiological, and nutritional situation. Although this supplement is a milestone along the way, there is still more way to go and to take advantage of the invaluable treasure that represents future follow-ups to the INCAP Longitudinal Study cohort.