Digestion - Children's understanding of what happens to the food that they eat

 Featured article

Teixeira, F. (2000). What happens to the food we eat? Children’s conceptions of the structure and function of the digestive system. International Journal of Science Education, 22 (5), pp.507–520

The children (aged 4 to 10) taking part in this study were each given a bar of chocolate and an outline, on paper, of a human body. They were asked to eat the chocolate and draw on the paper the parts of the body this food will pass through. The children were then asked to name any organs that they had drawn and to describe what happened to the food as it passed through each organ. They were also asked what the food would look like at each stage.

[AI generated impression of a child's drawing]

The study took place a private primary school in Brazil and the paper specifies that none of the children had had formal education about the digestive system. Clearly the outcomes may be different for children who have received scientific teaching about this during their primary years. However, the approach taken by the researcher and the outcomes still provoke some interesting questions about what children understand about what happens inside their bodies and how they build these ideas based on daily experiences.

The researcher analysed children’s drawings and explanations in terms of understanding of both structure and function. Clearly biologically these are linked as the structures inside the body all have a function. However, this distinction was designed to find out how much the children understood about the internal structure of their own bodies and how much awareness they had about the function of these parts.

The researchers categorised the responses based on three different broad ways of thinking about the path of food through the body:

1.  All food that has been ingested (eaten) remains in the body.

2. All the food that has been ingested eventually leaves the body.

3. Part of what has been ingested stays in the body but the rest leaves.

Broadly speaking number 1 was the predominant way of thinking of the four-year-olds in the study, number 2 was the more common thought process of the 6- to 8-year-olds and only for the oldest children (age 10) was number 3 the majority view.

At age four the most commonly used body part name was “tummy”. For children aged 4, 11% of children left the abdominal area in the drawing as empty space. The authors later comment that for a child that thinks all their food remains in the body this is not unexpected. There is no need for any other structures or compartments because the body is perceived as being simply a container. Interestingly for some of these children the only way food could leave their tummy was through moving down into their legs (or their arms if they bended). It was even suggested that the accumulation of food results in a stretching of the body. The children were aware (probably due to experience of chewing) that the food was broken into smaller pieces.

The children who thought that all the food that has been ingested leaves the body appeared to have some concept of physical change to the food but did not give any evidence of awareness that the identity of the food changed.

The oldest children showed some awareness of the limitations of the body realising that the body cannot absorb everything that is ingested. They also appeared to have some awareness of the idea that parts of food that are useful to the body are kept inside but other parts, which are not useful, leave the body.

Only six children (all older than 8) indicated that there maybe substances in the body that could modify others. This enabled them to conceive of the possibility that ingested food could be changed into something different to what it was. The idea of chemical transformation (change) was noted to be a complex one but difficulty with the idea was acknowledged to limit children’s explanations of the function of the digestive system.

Reflective questions

Primary (age 5-11)

The research suggests that even young children form ideas about what happens to the food they eat. What everyday discussion about food and eating may influence children’s reasoning?

e.g. An adult asking, “Is your tummy full?”

In what ways could the researcher’s approach of asking children to draw and then discuss what they think is inside their bodies be used in the classroom? How could the idea be extended to other topics?

What explanation of what happens to food when you eat do you think is acceptable for children aged 10 to 11 and what should be left for later learning?

Secondary (age 11-16)

In what ways could the researcher’s approach of asking the children to draw and discuss what they think is inside of them be used in a secondary context?

What chemistry learning is needed to support the development of biological understanding about digestion?

To what extent/ how do you build connections between the two subjects in your teaching?