From famines in developing countries to supplemental nutrition programs in developed ones, studies consistently conclude that nutrition is a fundamental input into health production, impacting both short and long-run health. Randomized-controlled trials that offer nutritional supplements to the treatment group have demonstrated that micronutrients play a key role in cognitive development. Assessing the direct impact of nutrition on health is difficult due to significant measurement error in the nutritional content of food items; therefore, most natural experiments examine how quantity of food relates to health outcomes. Research suggests that policies that improve the nutrition of pregnant women and infants will be effective at improving the health and human capital of the next generation.
The ideal setting for conducting research is the randomized-controlled trial, a technique that has been used in developing countries to study the impact of poor nutrition on cognitive development. In Jamaica, babies that were given nutritional supplements had higher mental development than the control group, indicating that lack of nutrition is a causal factor in stunted mental development. Children in Guatemala who received a nutritional supplement tested higher on knowledge, numeracy, reading, and vocabulary assessments than children given a placebo. The same children were followed up with as adults. Adults who were treated with the nutritional supplement as a child had higher reading comprehension, nonverbal and cognitive scores, and higher completed education (women only) than the control group.
The majority of economic research on nutrition in developing countries studies the impact of famines on health, education, and labor market outcomes. Famines are extreme events and estimating the impact of a famine can be confounded by selection because only survivors are observed. Furthermore, the health effects of a famine may not solely operate through nutritional deprivation – famines may affect other inputs to health and human capital such as disease- resistance and school attendance. The Chinese Famine of 1959–61 had a significant impact on children and babies in utero during the event. Children exposed in utero were shorter, lighter, and acquired fewer years of education than children born just before and after the famine. Exposure in early childhood had a detectable, yet smaller effect on long-term outcomes than in utero exposure. The famine also tilted the sex ratio in favor of girls, reduced the literacy rate, reduced employment, and reduced the marriage rate for children born during the time of the famine.
European famines during World War II had long-term impacts on health and human capital accumulation for individuals exposed early in life. Individuals who were in utero during the Dutch Famine experienced higher rates of chronic disease in adulthood. Children exposed to the Greek Famine during gestation and the first two years of life showed reduced educational attainment and literacy, with the largest impacts on children who were 0–12 months old during the famine. The impact of a famine can reach late into life – men exposed in utero to the Dutch Potato Famine of 1846–47 had a lower life expectancy at age 50 than cohorts born just after the famine.
Controlled nutritional deprivation for brief periods of time is associated with reduced physical and cognitive development, as evidenced by recent research into the outcomes of children in utero during Ramadan. Ramadan occurs for one lunar month per year and observance includes fasting between sunrise and sunset. In a study using data from the USA, Iraq, and Uganda, the authors document reduced birth weight, reduced gestation length, a decline in male births, reductions in educational attainment, and even increased rates of mental disabilities for children of Arab mothers in utero during Ramadan.
Even in developed countries, nutrition interventions can positively impact the birth outcomes of at-risk children as evidenced by analyses of the Supplemental Nutrition Program in the USA for women, infants, and children (WIC). WIC is aimed at low-income pregnant women and women with young children with the goal of improving the nutrition and health of this group. Consistently estimating the effect of WIC participation on infant health is difficult due to nonrandom selection into the program – unobserved maternal characteristics that affect infant health may be systematically different for mothers that choose to enter the program than for mothers who do not. Estimates that account for selection into the program yield a positive impact of WIC participation on birth outcomes such as incidence of low birth weight and gestation length. Infants at the low end of the socioeconomic and birth outcome distribution gained the most from WIC.