Children's Diets & The Benefits of School Gardens: A Report For The Princeton School Gardens Cooperative

By David Bejar, Rosa Mendoza, Rachel Rizal, Keerthi Shetty


The objective of the Princeton School Gardens Cooperative is to establish gardens at every Princeton public school in order to “re-connect students to the earth’s bounty in the garden, classroom, and cafeteria.”27 The members of the Cooperative hope that the gardens will increase students’ appreciation and intake of healthy foods such as vegetables and fruits. With the collaboration of principals, teachers, parent volunteers, and students, the organization has successfully designed and sustained gardens at six Princeton public schools. In addition, the Cooperative has written a guide to promote the in- tegration of the gardens with the classroom curriculum. The guide details the steps for composting, planning, and planting and also includes lesson plans and curriculum links for math, social studies, language arts, science, visual arts and health. In order to assist the Cooperative in its efforts to encourage healthy eating among the community’s schoolchildren, this paper: 1) outlines the unhealthy nature of child food preferences in schools; 2) provides an overview of the detrimental effects of poor nutrition on health, with an emphasis on the obesity epidemic; 3) offers evidence that healthy eating is correlated with increased cognitive performance; and 4) describes the success of garden projects across the country to highlight the importance and viability of the Princeton School Gardens Cooperative.

Recommended Dietary Habits

The Center for Nutrition Policy and Promotion, a department under the United States Department of Agriculture, establishes the national dietary guidelines. These guidelines are updated every five years, with the last revision conducted in 2005. The guidelines provide Americans who are two years and older with advice on good dietary habits that can promote good health and reduce the risk of chronic diseases.

The nutritional guidelines for children are usually presented in “My Pyramid.” 53 There are six groups: grains, vegetables, fruits, milk, oils, and meats & beans. A person’s allowance for all food groups depends on age and gender as follows.

Food Environment and Eating Behavior in Schools

Unfortunately, over the past 50 years, our children’s diets have changed significantly. They currently consume more sweetened carbonated beverages, fruit juices with added sugars, and fast foods rich in fat than ever before. 51 Because students spend many of their waking hours at school, a significant portion of their daily food intake is consumed there. In fact, in a study of U.S. children’s diets from 1994-1996, researchers found that children in elementary schools ate more meals at school than at any other away-from-home place. 31 Along with experimental and observational studies indicating that child dietary behavior 44 and body weight 27 are directly related to school food environments, these findings indicate that school cafeterias are a valuable and controlled setting in which to study the current state of unhealthy eating practices among our nation’s youth.

The National School Lunch Program (NSLP) of the U.S. Department of Agriculture’s Food and Nutrition Service is a federally assisted meal program charged with “safeguarding the health and well-being of the Nation’s children” by providing “nutritionally balanced, low-cost or free lunches to children each school day.” 40 In the year 2000, it was estimated that the NSLP provided meals to 95% of U.S. schoolchildren.^9^ The NSLP, however, fails to cover the full cost of preparing healthy, USDA-approved meals, and schools are forced to recover their losses by providing vend- ing machines, school stores, and snack bars that offer less healthy alternatives. 6 For example, in 2008, the government subsidy to schools was $2.57 per meal, while the average cost to prepare these meals rose to $2.88. 6 This 31-cent deficit provides a huge incentive for schools to sanction the sale of non-NSLP foods that raise revenue. Unfortunately, these foods lure children into making dietary decisions that favor taste over proper nutrition.

In 2005, a survey by the American Federation of Teachers revealed that nearly 60% of U.S. cafeteria workers agreed that when children are given a choice, they tend to choose prepackaged foods that are high in fat as opposed to healthier, more natural options. 26 In particular, vegetable and fruit dishes are among the most likely options to be dismissed in favor of foods that include pizza, chips, soda and french fries. 10 Researchers at the Baylor College of Medicine recently published a study that quantified the effect of having greater food options in school cafeterias on fruit, vegetable and milk consumption in Texas elementary schools. 10 The study compared fourth graders with access to only NSLP meals with fifth graders who had additional access to snack bar foods. The results indicate the extent to which children prefer less healthy foods: given snack bar options, student fruit, vegetable and milk consumption decreased by 33%, 42% and 35%, respectively. 10 Moreover, by the time the students reached the sixth grade, 35-40% of all meals were purchased exclusively from less healthy snack bars.

Studies conducted by researchers in the United Kingdom also portray the extent to which schoolchildren choose unhealthy foods more frequently than more nutritious options. Using smart card technology that recorded student food purchases to quantify the eating habits of children, Lambert et al. found that “fatty buns” (including cookies, muffins, and donuts) were over ten times more popular than fresh fruits and yogurt as the lunch dessert choice.28 Additionally, fizzy drinks and artificial fruit drinks containing greater amounts of sugar were over 20 times more popular than milk or fresh fruit juices. 28 The researchers also found that over a given school month, the amount of fat and added sugar intake could be reduced by 200 g and 800 g, respectively, if healthier drink and dessert choices were offered at lunchtime.

Given this information, there is no doubt that influencing eating behavior and food preferences, particularly when it comes to school lunches, are key factors to consider when implementing programs that improve the nutritional input of our children. Along with wider efforts to reduce the availability of unhealthy food options in school cafeterias, the Princeton School Gardens Cooperative’s mission of forging physical connections between students and the foods actively grown in school gardens represents a viable mechanism for encouraging students to eat more fruits and vegetables.

The Obesity Epidemic

Since the late 1970s, obesity rates have more than doubled among children 2 to 11 years of age and more than tripled among those of ages 12 to 19. 41 From 1963 to 1970, about 4.5% of children were obese. From 1999 to 2002, the number had increased to 16%, and continues to rise (Figure 1). Obesity is a complex phenotype which results from the interaction of multiple genetic, environmental, cultural, nutritional and lifestyle factors. 11 Although recent research has found that genetic factors are important in determining an individual’s susceptibility to obesity, our genes have not substantially changed during the past decades to account for the observed obesity epidemic. An important cause of the obesity epidemic is an environment that encourages behaviors (e.g. over consumption of calories and physical inactivity) that lead to obesity. 25

Unfortunately, obese children and adolescents are more likely to become obese as adults. 57,47 One study found that approximately 80% of children who were overweight at ages 10–15 years were obese at age 25. 57 Meanwhile, another study found that 25% of obese adults were overweight as children. 17 In addition, the latter study also found that if overweight begins before 8 years of age, obesity in adulthood is likely to be more severe.

Rising obesity is of great concern due to the serious health problems associated with it. For example, a study conducted by Weiss and colleagues examined the effect of different degrees of obesity in children on the prevalence of the metabolic syndrome and its relationship to insulin resistance. The metabolic syndrome is a group of risk factors including high blood pressure, high blood sugar, high cholesterol levels, and belly fat that increase the risk of heart disease and diabetes. The researchers found that the prevalence of metabolic syndrome is high among obese children and adolescents and that it increases with worsening obesity. 56 The direct link between obesity and the metabolic syndrome explains the rise of type II diabetes, a once rare disease in children and adolescents. In 1985, experts estimated that about 1-2% of children with diabetes had type II. By 1995, the number increased to approximately 17%. More recently, in some areas of the United States, 30-40% of children with diabetes have type II. 58

In addition to having a higher risk of acquiring type II diabetes, obese children are more prone to experience cardiovascular diseases, pulmonary diseases (such as sleep apnea), gastrointestinal problems, metabolic diseases (such as dyslipidaemia), coronary heart disease, and osteoarticular diseases. 3,4 Furthermore, there is substantial evidence that obesity is associated with risk for some of the most com- mon cancers including adenocarcinoma of the esophagus and the gastric cardia, colorectal cancer, postmenopausal breast cancer, endometrial cancer, and kidney cancer. 24

Unfortunately, not only does obesity affect the physical health of children and adolescents, but their mental health is also affected as obese children and adolescents are more likely to experience victimization than children with a normal weight. 22 A review of the literature on stigmatization of overweight children and adolescents indicates that overweight girls experience a higher degree of stigmatization than overweight boys. 49 This finding may explain why overweight girls are associated with a lower degree of aca- demic and social competencies. 12 In addition, certain studies demonstrate that for both boys and girls, obesity results in psychosocial consequences since the stigmatization of “fat” children by peers may lead to low self-esteem, social isolation, depression, and eating disorders. 49

Finally, obesity contributes substantially to health care expenditures. Obesity accounts for 5-7% of the national health expenditure in the US and presently surpasses both smoking and drinking in its harmful effects on health and health costs. 55 In 2002, the costs of treating obesity-related conditions such as diabetes, heart disease, renal fail- ure, and hypertension were estimated at $92 billion to $117 billion. Thus, whether paid by Medicare, Medicaid, or by private insurances, obesity-related health problems impose substantial costs not only on the obese but also on the general public. 23 Federal, state, and local policymakers must be aware that childhood obesity is a grave national problem and actions including strict measures that target the fundamental causes of obesity must be implemented.

One such measure is the establishment of programs that encourage our children to eat natural, healthy foods. As mentioned earlier, the Princeton School Gardens Cooperative maintains sustainable gardens in Princeton Public Schools and emphasizes the importance of learning through gardening. By encouraging students to eat the foods they grow, the Cooperative promotes eating habits that help prevent the onset of obesity and other related diseases.

Diet and Learning

Diet plays an important role in shaping cognitive capacities. When ingested food reaches the gut, the molecular systems involved in synaptic plasticity (the ability of the synapse to change in strength) and learning are triggered via the vagus nerve. 19 In addition, gut hormones and peptides, such as insulin and glucagon-like peptide 1 (GLP1) 35 are released after ingestion and travel to the hypothalamus and hippocampus. Here, the hormones activate signal-transduction pathways that modulate learning and memory through neural circuits connecting the gut and the brain. Furthermore, leptin signals from adipose tissue (fat) can activate certain receptors in the brain that impact learning and memory. 30,43,48 Additionally, insulin-like growth factor 1 (IFG1) produced by the liver and muscle in response to food metabolism and exercise can signal to neurons in the hypothalamus and the hippocampus and eventually in- fluence learning and memory performance by supporting nerve growth and differentiation, neurotransmitter synthesis and release, and synaptic plasticity. 14 Certain dietary factors can affect neural pathways associated with synaptic plasticity and can positively or negatively affect the brain. Thus, diet plays a critical role in shaping the cognitive capacities of the developing brains of children and adolescents.

Of course, not all foods are healthy – there are certain “brain foods” that are vital for healthy cognition. Dietary factors can affect the regulation of several brain processes, such as neurotransmitter pathways, synaptic transmission, membrane fluidity, and signal-transduction pathways. According to Dr. Gómez-Pinilla of the University of California – Los Angeles, people should consume more foods containing antioxidants, such as berries, nuts, and green leafy vegetables. 19 These antioxidant-rich foods are believed to protect synaptic membranes in the brain, which are very susceptible to oxidative damage. 34,59 Synapses connect neurons and are the site of much learning and memory activity. Accordingly, the Princeton School Gardens Cooperative should continue to plant antioxidant-rich berries, green leafy vegetables such as chard, kale, and spinach, and should also consider adding spices such as oregano, and nuts such as hazelnut.

A diet rich in polyunsaturated fatty acids, such as omega-3 fatty acids, has also been shown to be beneficial for the brain. Omega-3s, which are found in walnuts, flaxseed, winter squash, olive oil, fish, and soybeans, are known to improve learning, memory and concentration, and help prevent a range of mental disorders including depression, bipolar disorder, schizophrenia, dementia, attention-deficit disorder and dyslexia. 18 These fatty acids seem to have a positive effect on the expression of several synaptic molecules involved in learning and memory. A study performed in England showed that when children diagnosed with learning difficulties received omega-3 supplements for 6 months, they “tested a year higher in reading skills and 6 months higher in spelling” and were more focused than those who did not receive the supplements. 46 However, research indicates that more nutrition can be obtained from natural products than from the capsule supplements. 19 To grow foods that are rich in omega-3s, the Princeton School Gardens Cooperative should plant winter squash, soybeans, grains, and walnut trees.

Studies have shown that diets with a high concentra- tion of trans and saturated fats can negatively impact brain function and reduce the abundance of compounds involved in cognitive processing. 21 Trans and saturated fats are found in many of the foods schoolchildren eat, such as crackers, candies, cookies, snack foods, fried foods, baked goods, and other processed foods made with partially hydrogenated vegetable oils. 13 Studies testing the effect of “junk food” on rodents have shown that three weeks of a diet high in saturated fat and sucrose intake leads to a decline in cognitive performance. Reduced levels of brain-derived neurotrophic factor (BDNF)-related synaptic plasticity were also observed (BDNF is a signaling molecule that utilizes metabolic signals to influence cognitive function). 54 These findings were significant because they implied that diet has a direct effect on neurons independent of insulin resistance or obesity. 19

This connection between “junk food” and impaired cognitive abilities has direct relevance to the diet of American children. The 2008 School Lunch Report Card developed by the Physicians Committee for Responsible Medicine (PCRM) indicates that foods served in schools are too high in saturated fats and cholesterol and too low in dense nutrients that are present in whole grains, legumes, fruits, and vegetables. 45 The following case studies provide examples of schools that have introduced more nutritional foods in their lunches and have witnessed a positive association between quality diet and academic performance.

Case Study 1: California Schools

Schools in California have been very active in promoting healthier lunch options. Both low- and high-performing schools with students who eat healthy foods on a regular basis experience significantly higher gains in test scores compared to other schools. ^2^ “Healthy eating” was quantified by determining the average percentage of nutritious intake. This value was based on the number of times during the week the students drank 100% fruit juices and ate fruits, green salad, potatoes, carrots, and other vegetables. In contrast, undernourishment and skipping breakfast led to a decrease in test scores. The results suggest that more schools should mandate policies addressing the health needs of youth in order to improve academic performance. Although this study is purely retrospective and lacked a control group, the sample size consisted of an impressive 500,000 students; thus, the results cannot be ignored.

Case Study 2: Nova Scotia Schools

In 2003, the Children’s Lifestyle and School-Performance Study surveyed 4,589 fifth grade students and their parents in Nova Scotia to determine the relationship between indicators of diet quality and academic performance. 16 The study found that specific dietary factors, such as dietary fats (which are rich in omega-3s) and fruits and vegetables (which are rich in antioxidants) were crucial in lowering the risk of failing an elementary literacy assessment, independent of socioeconomic factors. The results also suggest an association between overall diet quality and academic performance.

Case Study 3: Agatston Research Foundation

Cardiologist Arthur Agatston conducted a two-year study which found that improving the nutritional quality of school food also improves students’ standardized test scores. 5 The study involved 1,197 elementary school students par- ticipating in the Healthier Options for Public Schoolchildren (HOPS) program. HOPS was designed to “integrate healthy dietary offerings, nutrition and lifestyle educational curricula, increased levels of physical activity, and school gardens” in central Florida schools. 1 During the study, the kids ate holistic foods – foods containing less saturated fat, no trans fat, and more whole grains, fruits, and vegetables. The results showed that the students’ math scores increased significantly.

Both scientific research and these three case studies provide preliminary evidence that improved diet quality is associated with improved cognition and academic performance. However, more research with additional controls needs to be conducted in order to confirm this link, especially with food that has been grown in school gardens. All of the case studies described above indicate that a diet including grains, fruits and vegetables contributed to increased academic achievement. These foods can be easily grown in Princeton school gardens and integrated into school lunches.

School Gardens

Positive Effects of School Gardens

Because healthy eating can positively impact the physical, mental, social, and academic aspects of children’s lives, schools can play an important role in influencing children to eat healthier. Incorporating school gardens into the curriculum allows children to have the opportunity to discover fruits and vegetables, make healthier dietary choices, and become better nourished. Several schools around the nation have implemented garden projects because principals and teachers believe they have the following benefits: increased nutritional awareness and physical activity, increased environmental awareness, higher learning achievements, improved life skills (teamwork, developing patience, responsibility, etc.), better youth development and leader- ship, and more community involvement.

Research reveals that school gardens influence children to eat healthier. Anecdotal evidence from teachers, in- cluding representatives from the Princeton Regional School District, indicates that students enjoy eating what they grow and are more enthusiastic about eating healthy foods. Studies corroborate these claims. Children who grow their own fruits and vegetables tend to have a positive attitude towards these foods and thus are more likely to eat them. 37,38,39,32 A recent study by McAleese and Ranklin indicates that garden-based nutrition education increases adolescents’ consumption of fruits and vegetables. 33 School gardens also increase children’s knowledge of nutrition. Schools have recognized that school gardens can benefit their students and communities in several ways. In order for school gardens to gain more popularity, educators and policymakers need to be convinced through more research that school gardens are a cost-effective resource for educating students.

The Successes of the Princeton School Gardens Cooperative

In the Princeton Regional School District, the Princeton School Gardens Cooperative has established school gardens in order to promote the benefits of connecting children to the food they grow. The Cooperative, started in 2006, has been successful in establishing a garden in every elementary school in the district. Middle and high schools in the district also have started their own gardens. The gardens contain a variety of fruits, vegetables, and herbs – everything from raspberries to parsley to cucumbers. One of the Cooperative’s most important accomplishments was to examine the district curriculum and match classroom and garden activi- ties to the state standards. This has helped teachers integrate their lessons around the school gardens. The Cooperative has also been successful in garnering support for the school gardens despite the fact that “there are no education standards driving them” (D. Mullen, personal communication, December 22, 2008). This stands in contrast to California, where the California Department of Education has pub- lished several lesson guidelines and plans to help teachers include school gardens in their lessons.

Many teachers and schools have found creative methods to integrate the gardens into the school environment. There are activities and lessons for several subjects: visual and performing arts, science, foreign languages, language arts, writing, math, and social studies. In Littlebrook Elementary School, for instance, sixth graders along with their first grade buddies created their own pizzas using the tomatoes from the garden. As part of their science class, students grew beans in varying degrees of sunlight exposure to learn about the effect of light on plant growth. In addition, students in clubs and extracurricular activities have been active in maintaining the gardens.

The Princeton school gardens have been very successful in gaining support from the community. Many parents and children volunteer to establish and sustain the gardens. Local businesses have also supported the Cooperative. The Bent Spoon, for instance, has donated proceeds and has used the herbs grown in the gardens for its ice cream.

Other School Garden Models around the United States

While the Cooperative has made tremendous strides over the past seven years, it can continue to benefit from other examples of school gardens in states around the U.S.. As mentioned earlier, California is a great example of a state that supports a school garden network.

At the school-level, the Cooperative should investigate the possibility of hiring permanent staff members and including a kitchen in its schools. The Edible Schoolyard at Martin Luther King Jr. Middle School in Berkeley, California currently has permanent staff members. Along with an enormous garden, the middle school has its own kitchen where classes are held so that children can use the plants they grow and cook food at school. The school has designated a kitchen chef and garden manager to ensure the sustainability and growth of the program.

California Universities have also provided research and support to the school garden network in the state. The University of California, Davis has a Children’s Garden program that hosts teacher training on garden-specific topics. 52 Likewise, the Princeton Cooperative has already started reaching out to nearby Universities. For example, it has collaborated with the Community-Based Learning Initiative (CBLI) at Princeton University to research the effects of school gardens on children’s health.

The California Department of Education supports and reaffirms the importance of school gardens. California funds numerous research studies that investigate the effectiveness of school gardens as well as the barriers they face. One study found that the greatest barriers for using gardens in academic instruction were found to be “a lack of curricular materials linked to academic standards and a lack of teachers’ interest, knowledge, experience, and training in relation to gardening.” 7 California has tried to address these two barriers by publishing Nutrition to Grow On (an activity guide that links nutrition to garden-based learning), Kids Cook Farm-Fresh Foods (recipes suitable for the classroom), and A Child’s Garden of Standards (instructional material that links specific activities to state standards in science, history, mathematics, and language arts). In addition, the government supports three School Garden Regional Training Centers that offer workshops related to gardening and garden-based nutrition. 8 The Princeton School Gardens Cooperative can learn from this example, and should explore the possibility of distributing instructional materials and conducting leadership workshops.

Schools in California are also able to apply for funding that supports school gardens. The California Instructional School Garden Program at the California Department of Education “has $15 million dollars in non-competitive, non-matching grant funds for school districts, county offices of education and charter schools who are interested in starting or sustaining a school garden program. Grant funds can be used for garden equipment, garden supplies and teacher/ school garden coordinator professional development.” 8 The Princeton Cooperative has benefited from the fact that Princeton is a fairly affluent community that has people with the financial resources to support school gardens. However, additional support from local businesses, the local government, and the state government can further expand its mission and programs. The Princeton Cooperative has garnered support from principals and community members in Princeton, and can continue to reach out to policymakers at the state-level in order to make a bigger impact on the children of New Jersey.


In conclusion, the growing body of evidence that indicates the unhealthy nature of child dietary behavior, and the detrimental health consequences that develop as a result, presents a convincing argument for developing programs that improve child nutrition. The Princeton School Gardens Cooperative has garnered substantial community support in its initiative to encourage Princeton children to consume greater amounts of fruits and vegetables, and should continue to incorporate individuals at the local and state level in order to expand the depth and breadth of its mission. Through these and similar efforts across the nation, communities can take an active stand to safeguard the health and wellbeing of our children – the bright future of our great country.

Subject: Public Health
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