Digestive Function in Infants and Children – Basics

The digestive system is like a long, one-way tube that takes in food (stomach), removes waste (feces), and in between extracts nutrients from food (the intestine – also called the gut, or bowel).

Initially, infants are only capable of processing a liquid diet, as they cannot yet break down solid food. Breastmilk provides a complete source of nutrition in a simple, digestible liquid form that is easily absorbed by the infant’s intestine.​ Milk formulas are designed to be like breastmilk in terms of nutritional composition.

As infants get older, their teeth and mouth enzymes can break down solids from 6 months of age. Their stomach fluids also become able to dissolve meat, cereals, fruit, and vegetables.

Further down, non-digested carbohydrates (dietary fibre) are digested by a population of billions of bacteria living in the gut called the microbiome. As a food ingredient, this is called “prebiotic” fibre, but in children, dietary fibre is just leftover plant carbohydrates that aren’t digested, and help form feces.

How does the Digestive System Absorb Nutrients?

The intestine is where all nutrients from food are sent into the body. When food leaves the stomach, it is mostly in a liquid form containing dissolved nutrients. About 15-30 minutes after feeding, these nutrients are slowly absorbed through the wall of the intestine, like tea through a tea bag.

The wall of the intestine is basically a folded-up filter, with enough area to cover half a badminton court, so it is very good at absorbing!^[1]

Some nutrients like amino acids (from protein), simple carbohydrates (like glucose), water-soluble vitamins (e.g., vitamin C, B-vitamins), and electrolytes (e.g., calcium, magnesium) get across very easily. Others, like fats, DHA, EPA, ARA, vitamins A, D, E, and K, need extra help because they don’t dissolve well.

When kids become ill through a gut infection, the intestinal wall becomes leaky and loses the ability to absorb. Also, bacteria and viruses can enter the gut, disturb the balance of gut bacteria, causing diarrhea and gas. They can even get into the body and cause infections in other places.

Digestive Health, Growth & Development

Apart from zinc, a lack of any nutrient can impact growth and development. The problem with trying to understand which nutrients are at fault is difficult because (a) they work together, and (b) children with malnutrition may be missing most of the key vitamins and minerals. So complete nutrition is very important in preventing these problems^[2].

This guide is for informational purposes only and should not be used to diagnose health conditions or make changes to medical treatments. Always consult with your healthcare professional for advice.