This article originally appeared in the January/February 1999 issue of Early Childhood News.

Early childhood programs exist to promote the cognitive, physical, social, and emotional development of young children with the central goal to safeguard the developmental potential of young children by maximizing social and educational opportunities. The admirable qualities of these programs, however, are undercut by a poorly addressed problem: childhood hunger. An estimated 19.5 percent of all U.S. households with children under age six are food insecure, and for Black and Hispanic households, this figure is about 30 percent (Brown & Cook, 1998). Comprising a significant segment of children in early childhood programs, these youngsters typically do not appear thin, but they are likely to be lethargic (especially before lunch or snack), seem apathetic toward their peers and caregivers, and have difficulty "tuning in" to the learning environment. A growing body of evidence reveals the significant role nutrition plays in early childhood development (Brown & Pollitt, 1996; Center on Hunger, Poverty and Nutrition Policy, 1998; Gorman, 1995; Grantham-McGregor, 1995; Levitsky & Strupp, 1995; Metallinos-Katsaras & Gorman, in press; Morley & Lucas, 1997; Strupp & Levitsky, 1995; and Wachs, 1995). This article describes the relationship of nutrition to cognitive development, and introduces the reader to the concepts of hunger and food insecurity as they relate to young children.

Hunger and Food Insecurity

The catch-all expression of "hunger" has technical manifestations within the scientific community. Hunger itself is considered to be the painful condition associated with the lack of food. Undernutrition and malnutrition are used interchangeably, but the former normally refers to inadequate dietary intakes which can adversely affect normal growth and weight gain in children. Malnutrition is associated with more advanced forms of undernutrition typical of developing countries. While such forms of malnutrition are rare in the United States, many poor children in the U.S. experience both "mild to moderate" undernutrition and actual hunger because of limited household incomes.

The presence of undernutrition in children is often determined by comparing individual measures to standardized growth curves. After considering possible compounding factors such as disease or heredity, low weight-for-height (underweight) or low height-for-age (short stature) suggests poor nutritional status. The National Pediatric Nutrition Surveillance System reveals that children less than two years of age who are enrolled in the Supplemental Food Program for Women, Infants, and Children (WIC) or other public health programs typically have twice the prevalence of low height-for-age compared to toddlers in the general population (in data derived from the third National Health and Nutrition Examination Survey). Data on children under five years old indicate that about eight percent of low-income youngsters are of short stature and two and a half percent are underweight (CDC, 1998).

Long before low-income children exhibit undernutrition through diminished height or weight gain, they experience on-going nutrient deficiencies. An analysis of food consumption data in children ages one to five revealed that a greater proportion of poor children had nutrient intakes that were below the Recommended Dietary Allowance for ten of 16 nutrients (Cook & Martin, 1995). These nutrients were total energy; folate; iron; magnesium; thiamin; zinc; and vitamins A, B-6, C, and E. As an example, 60 percent more poor children failed to meet the standard intake for iron when compared to non-poor children (Cook & Martin, 1995). A child’s iron status is not only a key indicator of dietary quality, but it plays a critical role in cognitive function (Schurch, 1995, and Morley & Lucas, 1997), as will be discussed later.

Evidence of hunger and undernutrition among children recently led the United States Department of Agriculture (USDA) to adopt specific categories by which to classify adults and children who do not have enough to eat. The new classifications describe hunger as formerly mentioned, and introduce the concept of "food insecurity."

Food insecurity is considered by the federal government to be: "Limited or uncertain availability of nutritionally adequate and safe foods, or limited or uncertain ability to acquire acceptable foods in socially acceptable ways." Food insecurity may occur on a regular or periodic basis, with or without hunger. Households with hunger experience "the uneasy or painful sensation caused by a lack of food, [or] the recurrent and involuntary lack of access to food." Hunger and malnutrition may be consequences of food insecurity (USDA, 1997).

Under the USDA classification, a food insecure family is considered to have "moderate hunger" if the parent misses meals because there is no food or money to buy food. Research shows that parents typically limit their own food intake to spare the children from food reductions (USDA, 1997). But when children themselves experience hunger due to a lack of food, the condition is defined as "severe hunger." If this situation persists, clinical signs of malnutrition, such as those previously mentioned, may emerge.

In developing the framework for food insecurity, moderate and severe hunger, USDA authorized a survey of food insecurity among households as part of the 1995 census. Of all U.S. households, about eight percent were food insecure, but households with children under the age of 18 years had higher rates in all categories of hunger and food insecurity. In these households, 13.4 percent experienced food insecurity without hunger and six percent experienced food insecurity with some hunger (USDA, 1997). In child-present households below the poverty line, 29 percent experienced food insecurity without hunger, approximately 13 percent had moderate hunger, and three percent had severe hunger (USDA, 1997). While all levels of food insecurity place children at risk for hunger and malnutrition, those who experience hunger are most likely to have substandard nutrient intakes and subsequent learning difficulties.

Nutrition and Cognitive Development in Children

Over the years researchers have gathered extensive evidence on the relationship between nutrition and child development, including cognitive functioning. New findings have shown the important link between diet and cognitive capacity (Brown & Sherman, 1995; Center on Hunger, Poverty and Nutrition Policy, 1998; and Pollitt, Cueto, & Jacoby, 1998). Until a decade ago it was believed that undernutrition, particularly malnutrition of a long duration, impeded normal brain growth and structure, and that this alteration impaired cognitive function. Because 80 percent of brain growth takes place during the first two years of life (Brown & Pollitt, 1996), inadequate nutrition during this stage of development was thought to impair cognitive function on a permanent basis. Recent evidence indicates that neither of these ideas adequately explains the interaction between nutrition and cognitive development. But there is both good and bad news.

First, the bad news. Evidence shows that the brain is far more susceptible to undernutrition than previously thought. In short, a child need not experience severe or prolonged malnutrition to experience altered cognitive function (Brown & Pollitt, 1996). Even "mild undernutrition," the kind most frequently found in the United States, impairs cognitive function—and can do so throughout the life of the child (Brown & Pollitt, 1996, and Wachs, 1995).

In infancy, a nutritionally adequate diet promotes growth and motor skill development. Infants and toddlers need to eat frequently and on a regular basis throughout the day to maintain the necessary level of energy for physical function and social interaction. When an infant or toddler does not have enough to eat, the body goes into a form of triage whereby the limited dietary energy is allocated on a priority basis (Brown & Pollitt, 1996). The first priority is to maintain critical organs. In this way the body insures survival of the organism, at the cost of all else.

The second priority for energy allocation is for growth, supporting normal height and weight gain (Brown & Pollitt, 1996). Many cities across America now have "failure to thrive" clinics in their hospitals. Children that are below the fifth percentile in weight or height receive medical care and nutritional supplements to overcome their lack of growth from inadequate nutrition.

Only after these needs are addressed can the energy that remains be used for skill building such as crawling, walking, and general exploration of the environment (Brown & Pollitt, 1996). By limiting energy available for interaction with parents, peers, and caregivers, undernutrition robs children of their ability to be inquisitive and interactive. The body of an undernourished child may be in the child care program, but his or her mind will be elsewhere. It is through this more subtle process, rather than actual assault on brain structure itself, that hunger cheats children of their natural potential.

The process can become self-fulfilling. Undernourished infants tend to be challenged less in terms of skill-building tasks as caregivers seek to adjust for their perceived inabilities. Indeed, many such children receive less engaging interactions from adults (Wachs, 1995). Furthermore, these infants and young children typically live in poverty conditions which restrict the availability of not only food, but environmental stimuli. The lack of educational opportunities in the form of books or toys, and exposure to poor family interactions and violence or stress compound the impact of their nutritional status (Grantham-McGregor, 1995; Metallinos-Katsaras & Gorman, in press).

But the recent evidence brings some good news as well. Initially it was believed that malnutrition during vulnerable times would permanently limit cognitive potential, primarily because needed dietary energy is unavailable during "development windows." Indeed, animal studies determined that brain growth is altered in response to acute episodes of malnutrition imposed during critical prenatal and early postnatal developmental periods (Levitsky & Strupp, 1995). Other studies have demonstrated that children who suffered from poor nutrition as infants have lower IQ levels, cognitive functions, and school achievement (Grantham-McGregor, 1995, and Gorman, 1995).

More recent research demonstrates the remarkable ability of the brain to recover from insult. The brain has greater "plasticity" than previously thought, meaning that if dietary energy is not available during the important window of rapid brain development, such development may be delayed rather than lost altogether. For many children (but not necessarily most), a sort of catch-up growth occurs which may alleviate longer-term functional impairments. In addition, when adequate nutrition is provided to undernourished infants, the positive or catch-up effects on cognitive function can remain through preschool (Gorman, 1995). While few long-term studies exist, one found that advances in reading, math, and other related areas persisted through the adolescent years (Gorman, 1995).

This good news-bad news scenario can best be summarized in the following manner: The brain is more flexible than previously thought, and undernourished children can benefit from nutritional and intellectual interventions; on the other hand, undernutrition is not a risk factor we should allow because it is known to be far more harmful—both in impact and duration—than previously appreciated. In short, even mild undernutrition impairs cognitive function in children, and the adverse impact can last a lifetime.

The Benefits of Child Care and School Meals for Young Children

With this knowledge, evidence of the benefits of dietary supplementation in programs serving children takes on added importance. This is particularly true of meals served in child care programs and elementary schools. In one clinical trial involving elementary school children (Pollitt & Mathews, 1998), those that consumed breakfast performed better on various psychological tests than children who fasted for 18 hours (this simulates the situation in which a child eats dinner around 5:00 p.m., goes to bed, and returns to school without breakfast). The tests assessed visual and stimulus discrimination and memory. More research is needed to determine whether the improved performances were related to a rise in blood sugar or by the body’s response to the stress of a fast. Regardless of the mechanism, breaking the overnight fast influences the ability of a child to remain attentive to details and to interact with his or her environment.

Other studies reveal the positive role of breakfast in academic performance. Participation in the School Breakfast Program correlates with reductions in tardiness and absenteeism (Cook, Ohri-Vachaspati, & Kelly, 1996), factors which contribute to academic success (Pollitt & Mathews, 1998). One study found that poor children receiving school breakfast scored higher on standardized achievement tests than their low-income peers who received no breakfast (Myers, Sampson, Weitzman, Rogers, & Kayne, 1989).

Children who consume breakfast also have greater dietary intakes, including key nutrients such as iron, calcium, vitamin C, vitamin A, and riboflavin (Kennedy & Davis, 1998). Iron is particularly critical for normal cognitive functions, yet 15 percent of all one- to two-year-old children in the U.S. have low blood hemoglobin (Federation of American Societies for Experimental Biology, Life Sciences Research Office), an indicator of poor iron status. Iron deficiency anemia, which reflects a combination of abnormal iron indicators, affects three percent of all one- to two-year-olds (Looker, Dallman, Carroll, Gunter, & Johnson, 1997).

Iron transports oxygen through the blood, and is found primarily in red meat, fortified cereals, grains, baby formula, and breast milk. Inadequate stores of iron reduce the ability of the blood to deliver oxygen to the muscles and brain, resulting in a general feeling of fatigue. Children with iron deficiencies have poor short-term memory and are less able to concentrate on tasks (Morely & Lucas, 1997, and Schurch, 1995); they may be irritable and aggressive or sad and withdrawn (Sizer & Whitney, 1994).

Impairments in behavioral and cognitive function in response to stress may remain after episodes of early undernutrition (Levitsky & Strupp, 1995, and Strupp & Levitsky, 1995), and children who start school chronically undernourished seem more vulnerable to the effects of extended periods without food. For instance, an undernourished child may perform equally to his or her classmates, but experience greater frustration working through difficult tasks. Those coming from households where food insecurity and/or hunger is the norm are in greatest need of dietary supplementation, and the evidence shows that meals served to young children in child care and school programs make a significant difference in their development and function.

• Be a Positive Role Model. While parents act as the primary role models and gatekeepers of a child’s diet, child care and preschool providers serve as important vehicles to introduce or reinforce positive habits in a supportive social setting. Teachers and providers can share meals with the children and incorporate the importance of food and diet in the daily curriculum.

• Involve Parents. Invite parents to share a special afternoon snack of exotic fruit and milk, or to join their child for breakfast or lunch. Use parent workshops to teach parents how to feed young children and promote healthful meals and snacks at home.

• Incorporate Food and Nutrition into Regular Program Planning. Invite parents to share traditional recipes that can be prepared in the classroom, or organize a potluck so that all families can enjoy various cuisines. Read stories about food and prepare food together. Plant herbs, taste-test less common fruits or vegetables, or make pretzels from scratch. Children who are exposed to food in a pleasant manner are more likely to try it, especially if they helped make the creation.

• Promote Healthful Practices. Whenever food is used in the classroom, take the opportunity to teach basic safety and sanitation procedures: wash hands, do not lick fingers or spoons or taste food before it is done, do not use sharp knives or other appliances without adult supervision, wipe spills, and clean up.

• Trust the Child. It is important not to unduly press a child to eat a food. The child can decide whether or not he or she is hungry or full. Just as adults vary the size of their meals from day to day, children do the same thing. As long as a variety of foods are offered, a child will generally eat appropriate amounts to support his or her growth and development.

• Know Your Resources. It is crucial that a family with limited resources be directed to sources of help. Your local WIC clinic, food stamp office, or social service agencies can help needy families. By encouraging a parent to use such services, you can help prevent undernutrition in the child.

Conclusion

We now have a better understanding of the ways in which nutrition affects the cognitive and developmental capacities of young children. Infants and toddlers who receive an appropriate diet develop motor control skills that help them explore their environment, play with games, and interact socially. These skills ready children for learning in the preschool setting, which then strengthens their subsequent learning development. If children miss critical developmental stages, or if they cannot absorb skill-building tasks at a young age, they may have difficulty progressing through later stages. In addition to supporting a stimulating educational environment, early childhood educators can maximize a child’s learning potential by advocating for nutrition education, acting as role models for healthful eating habits, and recognizing when a child may be at risk for undernutrition so that appropriate referrals may be made in a timely fashion.

J. Larry Brown, Ph.D., directs the Center on Hunger, Poverty and Nutrition Policy at Tufts University, where he is the Alexander McFarlane Professor of Nutrition and Health Policy.

Lori Marcotte, MS, MPH, RD, is the director of food and nutrition programs at the Center on Hunger, Poverty and Nutrition Policy at Tufts University, where she coordinates child nutrition education programs for low-income populations.

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