Agriculture Reference
In-Depth Information
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t u in t i in g
Stunting
, or linear growth faltering, is a clear expression of reductive adaptation. It
tends to occur most in infancy when normal growth in length is greatest. Its extent
can be described by comparing the child's height (or length, under 2 years) with
WHO standard or reference values for children of the same age. Below 90% or −2
standard deviation score (SDS or Z score) implies significant stunting, while below
85% or −3 SDS implies severe stunting (WHO 1999a). In many developing countries,
its prevalence is around 40% in those under 5 years old. Although puberty is late, so
that growth can continue for longer in the girls, adult height falls far short of that in
adults who were well nourished as children, which led in the past to the largely false
belief that the variation in adult heights in different countries was genetic rather than
environmental in origin.
Stunting, at the population level, is associated with impaired mental development.
Studies in Jamaica showed that mental development could be accelerated in stunted
toddlers with either extra milk or psychosocial stimulation. Sixteen years later, a
positive effect of stimulation remained (Walker et al. 2006). Physical development
is also impaired in children who are stunted; as short adults, their physical capacity
is reduced. Short females tend to have more complicated pregnancies and births and
children with low birth weights.
Reversal of stunting usually requires a major change of environment. However,
this did occur in boarding school children in New Guinea when they were supple-
mented with milk (Malcolm 1970). Doubt still remains regarding which nutrient
deficiencies are most responsible for stunting. Zinc deficiency is a good candidate in
theory. However, cows' milk is a poor source of zinc, so it is probably not the most
important deficiency. Other candidate nutrients include calcium, phosphate, sulfate,
iodine, and specific essential amino acids required for cartilage and bone growth and
structure (Golden 1991, Anonymous 1994).
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a is t i n g
Wasting
occurs when lean and adipose tissue grow too slowly or if the supply of
energy or nutrients is so low relative to demand that the body has to use its own
dispensable tissues to supply the demands of less-dispensable tissues like brain and
heart. Acute loss of fluid or nutrients often adds greatly to the demand side. Infections
(e.g., gastroenteritis or pneumonia) are the usual cause of increased demands. Such
situations occur frequently in young children living in poverty. Wasting can be
assessed as weight for height/length (discussed in the Stunting section) or as body
mass index (BMI) for age. When compared with WHO standard or reference val-
ues, below 80% or −2 SDS implies significant wasting, while below 70% or −3 SDS
implies severe wasting.
Wasting can be reversed rapidly, over a few weeks. However, if a child has under-
gone reductive adaptation and the wasting is severe, then mortality tends to be high,
up to 50% in many African hospitals (Jackson et al. 2006). By managing severe mal-
nutrition according to the principles outlined in the most recent WHO manual (WHO
