Pediatric Nutrition in Practice

1 Specific Aspects of Childhood Nutrition

Key Words

Protein · Amino acids · Requirement · Infants ·

Children

Key Messages

• A diet must contain a balanced mixture of all amino
  acids


• This can most easily be achieved by daily ingestion
  of animal protein; an alternative is a complemen-
  tary mixture of plant proteins
  © 2015 S. Karger AG, Basel

Introduction

Protein, derived from the Greek word proteos ,
which means ‘primary’ or ‘taking first place’, is
the major structural component of all cells in the
body. Proteins also function as enzymes, trans-
port carriers and hormones, and their component
amino acids are required for the synthesis of nu-
cleic acids, hormones, vitamins and other impor-
tant molecules.
The 20 α-amino acids which are part of pro-
teins are classified based on their nutritional im-

portance into indispensable (essential) amino

acids, conditionally indispensable (conditionally

essential) amino acids and dispensable (nones-

sential) amino acids ( table 1 ).

Protein in the body is in a dynamic state re-

ferred to as protein turnover, which involves con-

tinuous degradation to free amino acids and re-

synthesis of new proteins. The free amino acids

are a lso constant ly degraded and oxidized to car-

bon dioxide and nitrogenous end products, prin-

cipally urea and ammonia. Oxidation is an irre-

versible step and leads to so-called obligatory

losses. Dietary protein is necessary to replenish

these losses of amino acids to maintain protein

homeostasis. Furthermore, in children, there is

an increased need for dietary protein to allow

new tissue growth.

The requirement of dietary protein is there-

fore composed of two components: maintenance

and growth. The requirement of protein in chil-

dren and adults has earlier been analyzed in de-

tail [1–3] , and that of individual amino acids is

currently investigated but has not yet been de-

fined by the WHO/FAO.

Koletzko B, et al. (eds): Pediatric Nutrition in Practice. World Rev Nutr Diet. Basel, Karger, 2015, vol 113, pp 41–45
DOI: 10.1159/000367868

1.3 Nutritional Needs

1. 3. 3 Protein

Johannes B. van Goudoever

1