Pediatric Nutrition in Practice

1 Specific Aspects of Childhood Nutrition

Key Words

Nutrient digestion · Absorption · Fetal intestinal

development · Motility

Key Messages

• The fetal human gut is prepared for the digestion
  and absorption of nutrients already at the 24th
  week of gestation


• Macronutrients can be digested and absorbed even
  by premature babies


• The rate-limiting factor during fetal life, particularly
  for premature infants, is the development of motility
  © 2015 S. Karger AG, Basel

Introduction

Development of the gastrointestinal tract during
intrauterine life is the prerequisite for survival in
external life for a human fetus. The digestive and
absorptive capacity of the intestinal organs as well
as the contact of foreign pathogens with an active
immune system guarantees the normal growth
and wellbeing of an infant in early life. As the
number of premature babies below 1,000 g is in-
creasing, knowledge of digestive and absorptive
functions of the gastrointestinal tract is of vital

interest to neonatologists feeding these very-low-

birth-weight (VLBW) infants.

The gastrointestinal tract has digestive, ab-

sorptive, secretory and barrier functions. In ad-

dition it produces a large number of gut hor-

mones (e.g. the hormones ghrelin, peptide YY

and oxyntomodulin, regulating satiety; cholecys-

tokinin, regulating bile and pancreatic secretions

and motility; and glucagon-like peptides 1 and 2)

and hosts the majority of immune-competent

cells of the body, including about 80% of the

body’s immunoglobulin producing cells. The in-

teraction between various organs and the com-

plex structure and function of the gastrointesti-

nal tract is developing during fetal life in order to

provide the newborn baby with a functional gas-

trointestinal system to survive in the external

world. This includes the digestion and absorp-

tions of nutrients, transport through the gut as

well as a barrier function to a large number of

microbiota and symbiotic life with them. Anti-

gens need to be identif ied and taken care of with-

out involving the whole body in an illness.

The human gut is formed from the endoder-

mal layer of the embryo by the incorporation of

the dorsal part of the yolk sac during infolding of

the embryonic disk. At the 4th week of gestation,

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 83–86
DOI: 10.1159/000360320

1.7 Gastrointestinal Development, Nutrient

Digestion and Absorption

Michael J. Lentze

1