Growing a "Theory of Food"

In my book The Omnivorous Mind (Harvard Univ. Press, 2012) and in other writings, I have argued that we humans each have a "theory of food" that guides how, how much, and what we eat. This theory of food is analogous to "theory of mind," the suite of implicit cognitive skills that people use to negotiate the complex, interactive human social universe. Like language, we have a propensity to acquire a theory of mind, and both develop and become more complex over the course of childhood and adolescence. We have critical periods during childhood for the acquisition of language and theory of mind.

Like our first language and theory of mind, our theory of food is also something that is strongly influenced by our childhood developmental environments. I think almost everyone has an intuitive appreciation for the fact that dietary habits can be set when young. Less appreciated is just how powerful these cognitive dietary underpinnings can be. I suggest that these food-related cognitive processes combine to form a "theory of food" that has been adaptive for us over the course of our evolution as an omnivorous species. For an individual, a "first" theory of food may be as wired into the mind as strongly as a first language.

Studies of the development of food habits in children could shed light on the development of a theory of food. Is there evidence for a critical period?

Several recent studies conducted by scientists from the Centers for Disease Control and published in the journal Pediatrics (Volume 134, Supplement 1, 2014) suggest that the foods kids eat when they are infants help establish patterns for eating seen later in childhood. These studies emerged from a large-scale survey of the dietary and feeding habits of mothers and children called the Infant Feeding Practices Study II (IFPS). Infants were initially followed monthly beginning in the third trimester through the age of 12 months. The papers in Pediatrics are based on follow-up with these children at the age of 6 years.

Three of these studies are of particular interest, and are consistent with the idea that there is a critical period for developing a theory of food. Sohyun Park and colleagues looked at the consumption of sugar-sweetened beverages (including soda, fruit ades, fruit drinks, and sports drinks) during infancy and at 6 years of age (Pediatrics 134:S56-S62). They found that children who had consumed sugary drinks at some point during the first 12 months were more than twice as likely at age 6 years to consume them daily. Children have a natural preference for sweeter foods and drinks (easily available in modern as opposed to our evolutionary environments), which can ultimately lead to overconsumption, obesity, and the health problems associated with it. In fact, in a companion study lead by Liping Pan, children who had consumed sugary drinks as an infant were twice as likely as those who had not to be obese at 6 years of age (Pediatrics 134:S29-S35). The authors of these studies stress the importance of educating parents about healthy diet choices for their young children, which may be necessary to counter their natural preferences.

If eating unhealthy foods can be a pattern set in infancy, what about eating healthy foods? In another study from the IFPS, Kirsten Grimm and her colleagues (Pediatrics 134:S63-S69) found that among 6-year-olds, 31.9% ate fruit and 19.0% ate vegetables less than once a day--an amount far below recommended amounts. Looking back at what the children ate when they were babies, Grimm et al. showed that not eating fruits or vegetables was a pattern that could be set in late infancy--children who ate fruits or vegetables less than once per day as infants had much higher odds of exhibiting these patterns as 6-year-olds.

These children are developing food habits--theories of food--that reflect the nutritional environments provided by their parents and other caregivers. As the nutritional scientists who conducted these studies all agree, their results show that children's dietary habits are likely forming during infancy, which means that education and intervention to improve diet and health needs to start earlier rather than later. Changing it later can only be more difficult, as many of us are aware from personal experience.

A different take on defining the nutritional environment of children is provided in a recent paper by Bettina Cornwell of the University of Oregon and her colleagues (Appetite 81:277-283). In their studies of children ages 3-6 years, they found that a child's knowledge of the brands of foods high in sugar, salt, and fat, was a predictor of his or her body mass index (BMI)--high brand knowledge or awareness was associated with higher BMI. This finding was significant even after controlling for number of hours of television watched (which one might predict would increase brand awareness independent of dietary habits). Cornwell and her colleagues conclude that brand awareness might be a "test" of a child's implicit theory of food. Understanding the cognitive foundation of a child's food habits might be an important step in helping parents improve their child's diet.

Obviously, these developmental studies are not proof that a deep-seated, cognitive theory of food exists. However, they support the idea that childhood, stretching back to infancy, is a critical period in the development of food habits. This is consistent with a theory of food that, like other complex cognitive abilities, emerges from a common cognitive developmental pathway, but varies according to the learning environment.