FOOD PSYCHOLOGY

Daniel Roberts, Ph.D. & Brenda MacDonald, M.Ed.

Nutrition and Intelligence

Summary: From birth to old age, nutrition is a major determinant of everyone's health, intelligence and academic performance, as well as professional success and longevity. Research has shown that parents' income level correlates with their IQ and that of their offspring. Also, intelligence, as measured with IQ tests, predicts a range of academic, occupational, and life outcomes, including how long people live. Interestingly, the quality of one's diet also predicts a range of life outcomes. For instance, gifted students were much more literate about healthy food and had a much higher quality diet. Also, the rise in IQ test scores (the Flynn effect) over the past century were attributed, in part, to better nutrition, which helps students improve their health, and cognition. Intelligence and brain-related cognitive skills contribute to an individual's ability to learn, solve problems, and meet the adaptive demands of the society he or she belongs to. However, nutrition and mental skills are not the whole story; a number of other factors are involved in children and students' optimal growth and development. For instance, the home environment, parents' education and parenting practices were also strong predictors of development. Adoption studies are revealing to that effect. Studies of children adopted from infancy show that those reared in upper-class homes had higher IQ than children reared in lower-class families. Also, adopted children born to upper-class parents had higher IQs than those born to lower-class parents. In other words, intelligence is in part inherited as indicated by twin studies: adopted children' IQs as well as their MMPI profile is more related to biological parents. Nonetheless, adopted children from upper class families learn values, skills, and more, that help them to do better as a whole. Nowadays, nutrition education has become an important and integral part of the school curriculum to enhance health, brain function, and learning.

Nutrition, IQ and cognitive abilities

Current research points to higher cognitive abilities, intelligence, and school performance being positively correlated with a healthy diet. In that regard, the first 1,000 days of life are particularly important for brain development — and diet plays a determinant role. In fact, how the brain develops during pregnancy and the first two years of life defines how it will perform in a person's life span. It is a period in time when nerves grow and connect and get covered with myelin, creating the nervous system that will determine how a child thinks, feels and behaves, as well as the grown-up she/he will become. The neural pathways connecting brain areas affect a multitude of brain functions associated with learning, memory, attention, the ability to control impulses and mood, as well as the ability to plan.

Although critical stages of brain maturation occur early in life, the development of brain structures and higher cognitive functions (e.g. abstract thinking, deductive reasoning and problem solving) continues in childhood, adolescence, and into adulthood. The worldwide rise in IQ scores, known as the 'Flynn effect' (Martorell, 1998; Flynn effect. Wikipedia, 2019) was attributed to nutritional improvements among industrialized countries. Increases of 28 points in IQ has been recorded in the United States since 1910 and a similar increase was observed in Britain. On average, IQs in the West have increased about three (3) points per decade. The reasons for this increase in IQ were attributed to better nutrition, which helps students improve their health, a more complex school curriculum as well as greater access to media, all of which contribute to greater mental abilities.

Regarding diet, a study conducted in England (Smithers et al, 2012) reported that eight-year-old children who had a home-made contemporary diet (of herbs, legumes, cheese, raw fruit and vegetables) at 15 and 25 months of age had higher IQ scores on the WISC: a standard test of intelligence for children and adults (Wikipedia, 2021). On the other hand, at all ages, higher scores on a discretionary diet (characterized by biscuits, chocolate, sweets, soda, crisps) were associated with lower IQ. In addition, moderate-to-severe malnutrition during infancy is associated with a significant incidence of impaired IQ in adulthood that can have significant lifelong morbidity (Grantham-McGregor, 1995; Venables & Raine, 2016; Pizzol et al., 2021; Waber at al., 2013).

Other studies from around the world have also reported that a healthy diet during infancy, childhood and adolescence is associated with higher IQ (Bellisle, 2007, Isaacs et al., 2008; Theodore et al., 2009). Similarly, a better-quality diet during infancy and childhood was reported to have a positive effect on cognitive abilities, such as learning, memory and problem-solving skills (Cohen, 2016; Conners, 1989; Gale et al., 2009; Nurliyana, 2014; Nyaradi et al., 2013), Of importance is that children and adolescents' intellectual status and cognitive abilities early in life affected their food choices and therefore health into their senior years (Corley et al., 2013; Crichton, 2015; Whalley & Deary, 2001).

Nutrition and academic performance

Quality of diet and educational attainment has been researched among different age groups. Studies from a number of countries have found a positive association between a healthy diet and academic performance. Indeed, a healthier diet as defined by the Baltic Sea Diet Score (BSDS) and the Finnish Children's Healthy Eating Index (FCHEI) was associated with better reading skills but not with arithmetic skills, among children in Grades 1-3 (Haapala et al., 2016). However, low numeracy skills was associated with a higher Body Mass Index (Huizinga et al., 2012).

Similarly, a positive association between a healthier diet and academic performance was found in adolescents from Canada (Florence et al., 2008), Sweden (Kristjánsson et al., 2008), England (Feinstein et al, 2008) and the United States (Chikwere, 2019; Kim et al., 2016). In higher education, a positive association between eating behavior and academic performance was observed in female university students in Chile (Valladares et al., 2016). Furthermore, US College students who engaged in a healthy diet and lifestyle behavior had higher cognitive skills (Pilato, Beezhold & Radnitz, 2020).

Gifted children and nutrition

Gifted students are among the most knowledgeable about nutrition. A group of healthy students ranging in IQ scores from 85 to 130+ were tested to assess their knowledge and consumption of food. To that end, a questionnaire on the healthiness of food, healthy nutrition, and diet was developed with questions drawn from the Healthy Eating Index developed by the United States Department of Agriculture. The results of the study completed in 2007 indicate positive associations between IQ scores and knowledge of food, and healthy diets. However, gifted students and those in the superior range were more literate about healthy food and had a much higher quality diet than their counterpart.

Gifted students have scores of 130 or higher on the Wechsler Intelligence Scale for Children (WISC-V) or the Stanford-Binet test (SB5). The fifth edition of the WISC provides a full-scale IQ score and five composite scores of specific cognitive processing domains: verbal comprehension, fluid reasoning, working memory, visual-spatial, and processing speed. Gifted scores on an IQ test fall in the top 2 percent of the intelligence bell curve. Their IQs do not mean that they are good at everything; nonetheless, being gifted involves higher cognitive abilities (e.g., verbal and nonverbal skills, learning abilities, memory, concept-formation, creativity, and problem-solving skills) that are associated with longevity, higher school performance, and greater job success (Deary, 2012;Duggan & Friedman, 2014; Reynolds & Livingston, 2012).

Let's point out that gifted students also perform well in other realms of intelligence, such as the types of intelligence described by Howard Gardner (2011). Gardner's theory of multiple intelligence broadens the notion of intelligence to include eight different types of intelligence consisting of Linguistic, Logical-Mathematical, Spatial, Bodily-Kinesthetic, Musical, Interpersonal, Intrapersonal, and Naturalist. Howard Gardner's theory postulated that children are not born with all of the types of intelligence, as for the reason they are often taught in school as part of the gifted curriculum. The upgrading and updating of these intellectual abilities will further contribute to their success in academic, professional, and social life, as well as other life endeavours.

Parents teaching dietary habits to offspring

It goes without saying that gifted students and their parents have lots in common, and for one, they share the same diet. Of course, in sharing one household, parents and their offspring share the same food and have similar eating habits. However, not all gifted students (about 1 out of 5 or 20% of them) are high achievers. Even when they don't get good grades in class, they tend to score high on achievement tests, most often in the 95-99th percentile. As adults, they also manifest trouble in their career and social life.

Observations from working in schools, and parents' discussions, has led us to state that factors, other than diet, influence gifted students' performance in school and in adulthood. For instance, heightened emotional sensitivity, low intrinsic motivation and nonconformity have been associated with their performing lower than expected in school. Studies have pointed to low levels of emotional intelligence that put them at risk for social and emotional problems. Gifted children with ADHD are usually low in emotional intelligence because their disorder affects brain areas associated with managing emotions (Lovecky, 2003).

Parental factors related to offspring's cognition

Let's be aware that a number of parental factors are involved in their offspring's growth and development. Parental factors that influence offspring cognitive development include the social environment, family systems, parents' education and personality, and their socioeconomic status. Low-end socioeconomic status (including poverty) hinders secure access to quality food-food that contains essential nutrients, such as fresh fruit and nuts and so on, and this lack of quality food then leads to poorer health. Manyanga et al (2017) provided evidence of diet-SES gradients across all levels of human development and found that lower within-country SES is related to unhealthy dietary patterns. In turn, unhealthy dietary patterns have been shown to correlate with life style risk factors leading to poorer parental health and offspring development (Barger et al, 2019; Flouri & Buchanan, 2010; Power & Elliot, 2009).

At the other end of the socioeconomic scale, Terrisse et al. (1998) carried out a study of the effects of the family environment. Forty 2-parent families with a child 4–6 years old participated in this study. Parents completed the Family Environment Questionnaire (FEQ) while children were administered the Development and Maturity Inventory for Preschool Children (DMIP). The Home Observation for Measurement of the Environment (HOME) was also administered to each family. Results show that children from a more advantaged milieu, according to the FEQ, where the home environment was more stimulating, according to the HOME, received higher scores in the motor, social, language, and cognitive developmental domains of the DMIP. Mothers significantly influenced the child's language and cognitive development, while fathers' influence was more evident on the child's motor and social development. Interestingly, however, parental attitudes and parenting practices (e.g., authoritarian vs. authoritative parenting) better predicted child development than did education and socioeconomic status.

Cox & Harter's (2003) review concluded that it is the relationship between the parent and child that is critical for the positive development of children. Parents who foster intellectual development avoid being too restrictive, punitive, or controlling, instead giving their children room to explore and come to their own conclusions. In a similar vein, parents whose children have higher developmental scores ask questions rather than give commands. Most also provide an interesting and complex environment that includes books and play materials. Family interactions also foster high scores; parents interact with their children and operate in what Vygotsky (1978) refers to as the zone of proximal development, aiming their conversation, their questions, and assistance at a level that is just above the level children can manage on their own, so as to help children master new skills.

Heredity and environmental factors on IQ

Twin studies and studies of adopted children show a strong heredity influence on IQ. Identical twins are more like each other in IQ than are fraternal twins, and IQs of adopted children are better predicted from the IQ of their natural parents than from that of their adoptive parents (Brody, 1992, Loehlin, Horn, & Willerman, 1994; Scarr, Weinberg, & Waldman, 1993). Interestingly, a study found that adopted children's MMPI profiles were more similar to that of their biological parents than adoptive parents. All the children were adopted in the first year of life and were on average 18.5 years at the time of the study (Scarr & Weinberg, 1983). The Minnesota Multiphasic Personality Inventory, MMPI test, is an evaluation of an individual's personality traits as well as psychopathology to determine the presence of mental health issues.

Adoption studies do, however, provide support for an environmental influence on IQ scores. In fact, the home environment and family interactions are shown to impact positively on adopted children. On average, children adopted in upper-class families show a gradual increase in IQ to the order of 10 to 12 points (Wahlsten, 1997; Schiff & Lewontin, 1986). On the other hand, when deprived children remain in their impoverished environment, they either show no improvement in IQ or their intellectual and cognitive skills as well as social abilities deteriorate over time (Serpell, 2000).

Capron & Duyme (1989) reported evidence of the impact of the home environment on a group of 38 French children who were all adopted in infancy. About half the children had been born to better-educated parents from a higher social class, while the other half had been born to working-class and lower socio-economic class parents. Some of the children in each group had then been adopted by parents in a higher social class, while the others grew up in families of lower socioeconomic status. The children reared in upper-class families had IQs 15-16 points higher than those reared in lower-class families, regardless of the social class level or education of their birth parents. As well, adopted children born to upper-class parents had higher IQs than those from lower-class families, no matter what kind of environment they were reared in. In other words, intelligence is inherited, with the environment also playing a role.

Let's remember that scores on general intelligence correlated around 0.40 (or 40%) with the socioeconomic status of the family in which adopted children were reared (Lubinsky, 2000). This is a fair correlation, but by no means a strong correlation. Also, there are some caveats with both IQ scores, as well as IQ correlations; IQ tests measure a child or adult's general mental ability that is determined by the g factor advanced by Charles Spearman. Kundel et al (2004) performed a meta-analysis of 127 studies involving 20,352 participants in numerous educational and work settings. Their study concluded that the same mental ability (the g factor) was significantly related to academic performance and work. Although a score of general intelligence is useful, for practical purposes, cognitive processing theories of intelligence better predict students' academic performance, and are used to match students with specific career requirements.

In IQ correlation studies, the term correlation indicates linearity; these studies do not determine other variables or factors that have an influence on the adopted child, or children in general; such as the family's socio-economic status, the adoptive parents' education and profession, the education of the adopted child, the culture and environment, family influence, nutrition, exercise and health. Ultimately, these variables will stimulate the growth of brain areas associated with all facets of people's intellectual abilities, including Howard Gardner's multiple intelligence (2011), Sternberg's triarchic theory of intelligence that emphasizes creative intelligence (2002), and Daniel Coleman's emotional intelligence (1995) and social intelligence (2006).

By the way, studies in neuroscience have investigated how intelligence is linked to specific regions of the brain. The consensus is that specific brain areas are associated with different forms of intelligence. The most prominent finding from brain imaging studies is that a neural network connects areas of the brain associated with language, visual-spatial skills, emotional abilities, and other regions of the brain (Deary, 2010; Colom et al., 2010). It goes without saying that new technology will bring more insight about the brain's role in intelligence. Also, let's remember that the various forms of intelligence have developed over time so humans can adapt to more complex environments. Of importance is that evolutionary theorists postulate that both diet or nutrition, and environmental factors have, and continue to influence the growth of various brain areas associated with specific forms of intelligence which, through the nerve pathways, have a real impact on an individual 's cognitive abilities, and social functioning.

Nutrition education in schools

A significant number of children and adolescents have become overweight due to unhealthy food choices and lifestyle habits, a trend that has led to a greater occurrence of hypertension, diabetes, and high cholesterol. School boards across the U.S. and Canada have implemented health and nutrition courses as a part of their curriculum. The course content has students learning how modern technology has replaced most of the physical activity at home, at work, and in transportation. Watching television, surfing the internet and video gaming are described as sedentary activities contributing in several ways to weight gain. Moreover, television and the internet advertise foods high in sugar and fat content. Because high-sugar foods taste good, teens eat more, and along with fat being not satiating enough, teens are led to eat even more sugary foods.

Psychologically, students who participate in nutrition courses and have experienced weight loss report facing less social discrimination and stereotyping, leading to greater self esteem, less stress, and some appreciating the aesthetic of a fit body. Of importance is the ripple effects of nutrition programs, particularly the health benefits. Teens who have graduated from these programs have become much healthier, with enhanced learning and did significantly better in school. As graduates of these nutrition programs, they learned cognitive-behavioral techniques (CBT) and, to how to adopt a positive attitude. Indeed, teens who made permanent lifestyle changes, such as making healthy food choices and continuing to be engaged in physical activity, aspire to greater things in life, because of a more positive self-concept, and body image.

In spite of their initial optimism, teens are often at high risk of relapsing, considering that their health-related behavior, including eating habits, have become established by age 12. Stress can contribute to a relapse as it is tied to consuming more fatty foods and less fruit and vegetables, and to the likelihood of skipping breakfast, with more snacking between meals (Cartwright et al, 2003). We have found that stress is associated with fatigue, leading people to eat more so as to have energy for incoming activities. Much dietary change has been implemented through cognitive-behavioral interventions. However, family interventions were also, for several good reasons, helpful in having teens adhere to a new diet. Having parents and their teens collaborate together gets them closer, helps them understand generation differences, and establish happier and stronger bonds.

Given climate-related threats to global food production, and the important role that diet plays in preventing chronic disease and in supporting good health, schools have taken a greater role in teaching students how these issues impact them. As such, nutrition education has become an integral part of the curriculum in schools in western countries. This has led students to have a greater overall knowledge of nutrition and health as well an understanding of the importance of food and diet in enhancing their learning, emotional and mental wellbeing, and in preventing chronic disease.

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