Baby’s Digestion – What Do I Need To Know?

Why do digestive disorders occur in babies? To eliminate them in time, you need to know about some peculiarities of the gastrointestinal tract in infants.

Almost every new mother in the first months of life experiences colic, regurgitation, diarrhea (frequent liquid stools), constipation and flatulence.

Most often these disorders of the digestive system are functional and due to the general immaturity of the gastrointestinal tract organs of the baby at the time of birth, low activity of digestive enzymes, immaturity of the nervous system, which disrupts the motor function of the intestines. 

Breastfeeding is a natural process and nature has designed the immature gastrointestinal tract during the first months of life to be mainly adapted to absorb only breast milk. That is why infants who are breastfed from birth are much less likely to have various functional disorders of the digestive system. 

Digestion in the child under a year: what is needed for comfortable suckling

A baby’s digestive system begins with the oral cavity, and the structure of the mouth has a number of anatomical and physiological features that ensure that the baby’s mouth is best suited to sucking and eating liquid food. These include:

trunk-shaped lips with well-developed muscles, so that the baby tightly encloses the mother’s breast with his lips;

the gingival membrane, a roller-shaped thickening on the alveolar processes of the upper and lower jaw that seals the baby’s mouth while sucking;

Biceps – dense fatty formations between the cheek muscle and the superficial facial muscles that help to maintain the negative pressure created in the mouth when sucking;

well-developed tongue muscles that allow the baby to make wave-like movements with the tongue when sucking, creating a vacuum and helping to squeeze milk from the nipple;

to squeeze milk from the mother’s nipple, the baby moves the lower jaw to the front. This way it engages the nipple, making rhythmic movements from front to back. These movements in infants are possible because of the poorly defined articular tuberosity of the temporomandibular joint.

For feeding, it is not only important for the baby to suckle on the mother’s breast, but also to breathe freely during feeding. Nature has also thought of that: the high position of the larynx in newborn babies causes the epiglottis (the movable cartilage that covers the entrance to the trachea) to be a little higher than the tongue root, which enables the baby to suckle and breathe at the same time.

On the way to the stomach

From the mouth, food travels down the esophagus to the stomach. The main feature of the esophagus in infants is the functional incompleteness of the sphincter (muscular ring) that separates the inside of the stomach from the esophagus. This is the so-called cardiac sphincter, which consists of annular muscle fibres that normally close after the passage of food from the esophagus into the stomach. This prevents gastric contents from being carried back into the esophagus. At birth the cardiac sphincter is weak and underdeveloped and therefore gastric contents are thrown down the esophagus and into the mouth, resulting in regurgitation or vomiting. 

Another factor that predisposes to regurgitation is that the stomach in infants is horizontal and only becomes vertical when the infant begins to walk. The angle of entry of the esophagus into the stomach (Gis angle) in infants is often blunt or approaching 90┬░, which in turn creates conditions for the gastric contents to be thrown down the esophagus. 

If the infant regurgitates infrequently (1-2 times a day), in small amounts (1-3 tablespoons) and has a good appetite and regular stool, the regurgitations may not be considered important as they are most likely related to the age-related features of the gastrointestinal tract. 

Often and a little at a time

The baby’s stomach after birth is relatively small. For example, the physiological capacity of the stomach in newborns is 30-35 ml, increases to 150 ml by 3 months and to 200-250 ml by one year of age. Knowing the anatomical-physiological features of the baby’s digestive system, it is clear that the stomach in the first months of life is designed to receive milk in small portions, for which feeding on demand is ideal – a feeding regime in which the intervals between feedings and the duration of sucking are set by the child. If the intervals between feedings are extended to 3 hours, the baby needs far more milk than it can absorb to satiate, which leads to overstretching of the stomach and regurgitation. 

How is food digested in the stomach?

The secretion of gastric juice and the activity of its enzymes are low in the first months of the child. For example, the gastric juices of newborn babies have almost no hydrochloric acid, so the acidity of the gastric juices is very low (maintained by lactic acid) and sufficient only for digesting and absorbing the proteins of breast milk.

Gastric juice contains proteolytic enzymes (pepsin, gastrixin, rennet and lipase), which are involved in the breakdown of milk proteins and fats. Breaking down fats in breastfed babies is much more vigorous than in formula-fed babies, as the former have this process in the stomach not only due to the enzyme lipase in gastric juice, but also due to the lipase in woman’s milk. 

Because the nutrients in breast milk are in a form that is easier to digest, breast milk is quicker and easier to digest than formula. Breastfed babies can therefore breastfeed as often as they want. However, an interval of 3 to 3.5 hours between feedings is recommended for children on artificial feeding, as proteins, fats and carbohydrates take longer to digest. 

Motor activity of the stomach in children in the first months of life is sluggish, which is associated with insufficient development of neurohumoral mechanisms and a poorly developed muscular layer of the gastric wall.

The timing of the evacuation of food from the stomach depends on the nature of feeding. Thus, female milk lingers in the stomach for 2 hours, milk formula for a longer time – up to 3-4 hours, and this should be taken into account when formulating the diet of the baby. 

As the stomach becomes free of food, the excitability of the food centers, i.e. those parts of the brain that regulate the digestive organs, begins to increase. The baby develops sucking motions. The excitement spreads to other parts of the brain, which causes the baby to wake up and begin to move and worry, and may even cry. 

Baby’s digestion: In the intestines

When food enters the small intestine, namely the duodenum, the complex process of breaking down and absorbing nutrients begins with the combined action of intestinal juice, bile and pancreatic secretion. The pancreas secretes enzymes necessary to break down food substances: proteases that break down proteins, lipase that breaks down fats and carbohydrates that break down carbohydrates.  Due to the immaturity of the pancreas in infants these enzymes are excreted in small quantities but they can easily break down easily digestible nutrients found in mother’s milk or formula. If the child is artificially fed, the pancreas matures more quickly due to the fact that it works harder to break down the proteins in the formula. In babies fed with breast milk, the pancreas matures during the introduction of complementary foods. 

Bile plays an important role in digesting fats but as little bile is excreted in the liver in infants, the infant’s body does not do well in digesting fatty foods.

The small intestine produces the enzyme lactase, which breaks down lactose (milk sugar) into glucose and galactose, which are well absorbed in the large intestine. If lactase is not active enough, the uncracked milk sugar enters the large intestine where it decomposes and causes various digestive disorders in the child, such as increased gas (flatulence) and runs (diarrhea). 

Intestinal motility consists of pendulum-like movements that occur in the small intestine, which mixes its contents, and peristaltic movements that move the food lump towards the large intestine. 

The small intestine of a baby is longer than that of an adult and does not have coordinated muscle work to move food from the stomach to the rectum. Therefore constipation and bloating are common in babies.

In infants the duration of passage of food mush through the intestines is between 4 and 18 hours.

The stools of the baby vary at different ages and depend on the type of feeding. A characteristic feature of the digestion of newborns is the presence of meconium, the feces produced in the intestines of the fetus. It is excreted in the first 24 hours after birth and is dark green in color. Then the stools turn brown and, after the fifth day of life, golden yellow. The feces of a formula-fed baby are lighter in color, have a thicker consistency (as formula is less absorbed and therefore constipation is more common) and have a stronger smell.

A breastfed baby normally passes stools up to 6-7 times a day. A breastfed baby may have stools as many times a day as he or she is fed. In an artificially-fed baby this is usually less frequent, about 2-3 times a day. Exchanging breastmilk with complementary foods causes the stools to be less frequent and the child has to go “poop” once or twice a day by the age of one. 

Protection is not good

Your baby’s oral mucosa is very delicate and easily injured. Little saliva is produced and the oral mucosa does not get enough moisture. Dry mouth makes it vulnerable to micro-injury and infection. Low salivary bactericidal function is also due to the low content of lysozyme and secretory immunoglobulin A in saliva.  

Who lives in the intestine?

The baby’s intestines are sterile at birth but from the first day onwards, when colostrum enters the digestive tract, it begins to be inhabited by beneficial microorganisms. In healthy babies who are fed breast milk, the intestinal flora reaches normal levels by the end of the second week of life. During breastfeeding the main flora are bifidobacteria, whose growth is promoted by the beta-lactose of the woman’s milk. 

After the introduction of complementary foods and when transferring to complementary feeding, the intestines become dominated by Escherichia coli, which are classified as opportunistic bacteria. Normal digestion in the intestine is largely determined by the microflora, which plays a huge role in the digestive processes. Intestinal bacteria enhance the hydrolysis of proteins, ferment carbohydrates, saponify fats and dissolve fiber. Normally, they contribute to enzymatic digestion and are also involved in the formation of B vitamins and vitamin K.

Stool retention and constipation: what is the difference?

If the baby empties the bowels once every few days, during defecation the stool is of normal volume and consistency (mush), the child is not bothered (he is active during waking, does not cry for no reason, sleeps peacefully) – the mother should not worry and take any action. In this case, it is most likely a functional bowel disorder and delayed stools in the baby. True constipation can be suspected if the child has delayed bowel emptying, small amounts of hard stools (stools like “goat balls”) and painful defecation.

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Author: Doris Cory

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