can lead to extreme behaviour. A recent study of
American adolescent athletes found that over a
third were taking vitamin/mineral supplements
and that over two thirds believed that such
supplementation was improving their athletic
performance (Sobal & Marquart 1994). This is
despite the consensus in the nutrition litera-
ture that supplements do not help performance
(Haymes 1991). Such findings suggest that im-
proved education and dietary counselling are
necessary to clarify such issues.
The first part of this review discusses the inter-
actions between nutrition and a child’s normal
growth and the effects that training may have on
growth. The second part concentrates on nutri-
tional requirements for performance.
Nutritional requirements of the
growing child
From birth to approximately 10 years of age, chil-
dren are highly dependent on their elders for
their nutritional requirements and dietary habits.
Studies of the nutritional requirements for this
age group have been relatively neglected, apart
from infant nutrition. Healthy boys and girls
are expected to gain around 30 cm in height and
12 kg in weight between 5 and 10 years of age
(Tanner 1989). Whilst percentage body fat
remains fairly constant in boys during this
period, it usually increases slowly in girls
(Forbes 1987). At this age there is a consider-
able need for energy and essential nutrients for
growth. In girls, sexual maturation begins
around 8 years of age and this also affects nutri-
tional requirements. For most essential nutrients,
requirements for schoolchildren have been esti-
mated by interpolating between infant and adult
data, which raises concerns with regard to the
validity of these estimated requirements.
The next stage of childhood growth is
adolescence (10–19 years). Adolescence includes
puberty, which consists of characteristic devel-
opment of biological age, which differs in boys
and girls, and leads to ‘final’ adult height, shape,
body composition, and physical and sexual
function. This hormonally driven development
430 special considerations
involves a linear growth spurt which commences
about 2 years earlier in girls (around 12 years of
age) than boys, acceleration of growth of muscle
in boys and adipose tissue in girls, the emergence
of secondary sexual characteristics and finally, in
girls, menarche, or the onset of periods (Tanner
1989). Once menarche is attained, girls lose blood
(on average 44 ml) approximately every 4 weeks.
This loss of blood is equivalent to a loss of
12.5mmol iron · day–1. However, there is wide
variation in blood loss among girls, with the 95th
centile estimated at 118 ml · period–1, or 34mmol
iron · day–1(Hallberg et al. 1966). Consequently,
the iron requirement for postmenarcheal girls is
higher than for boys, and much higher than the
prepubertal requirement.
In boys, the linear growth spurt is greater than
in girls and is accompanied by accelerated
muscle growth. Boys’ nutritional requirements
therefore rapidly diverge from those of girls.
During this time, bone density increases quickly
by the incorporation of calcium and phosphate.
It is estimated that 25% of peak bone mass is
acquired during adolescence. Studies have
shown positive effects of increasing the intake of
dairy products on bone-density development
(Leeet al. 1996). Although there is clear evidence
that calcium intake during growth influences
bone mineral density (Barr 1995), debate still
exists as to the levels of calcium intake required.
It also appears that physical activity is at least as
important an influence on the increase in bone
density in adolescence (Welten et al. 1994).Adolescent dieting behaviour
Adolescence is the peak period for dietary
change, from self-imposed dietary restraint to
veganism and beyond. In girls, dieting to reduce
weight, whether needed or not, is common, par-
ticularly in some sporting events. While adoles-
cent boys tend to exercise as much or more than
previously and eat as dictated by appetite, girls
today tend to eat towards a thin body ideal, and
exercise less than previously.
The complex and ill-understood illnesses,
anorexia nervosa and bulimia nervosa, almost