Agriculture Reference
In-Depth Information
effect or a detrimental effect on development in three others (Hamadani et al. 2001,
2002, Black et al. 2004b).
It is likely that other nutrient deficiencies confounded these trials since children
with zinc deficiency because of a poor diet could be expected to have deficiencies
of other micronutrients. When zinc was given with or without additional iron, there
were benefits to motor development and behavior in one study (Black et al. 2004a)
but not in the other (Lind et al. 2004). The only study with a benefit to global devel-
opmental scores showed this effect only when zinc supplementation was combined
with a psychosocial stimulation intervention (Meeks Gardner et al. 2005). It is pos-
sible that even if children become more exploring and active with zinc supplements,
improvements to development may only occur if their environments provide ade-
quate stimulation.
The role of zinc deficiency in children's development remains to be clarified. Zinc
status is difficult to measure, and response to supplementation is often used as an
indicator of deficiency. Possible explanations for the lack of response in develop-
ment in some studies could be that the children were not initially zinc deficient, that
additional deficiencies affected development, or even that zinc given as supplements
produced imbalances in other micronutrients.
vItAmIn A
Vitamin A deficiency is associated with increased frequency and severity of infec-
tions, increased mortality, and vision impairment. Effects on vision would almost
certainly have detrimental effects on children's development, especially where facil-
ities for the visually impaired are lacking.
In one study, Indonesian mothers were supplemented with iron and folate only
or iron, folate, and vitamin A during pregnancy (Schmidt et al. 2004). Vitamin A
produced no benefits to the infants' mental or motor scores at 6 or 12 months of age.
However, there was a suggestion of an association as maternal vitamin A status in
pregnancy was related to infant mental and motor development outcomes. Two stud-
ies looked at vitamin A supplementation of young children and their developmental
outcomes. In one, Indonesian newborns given vitamin A had slightly higher scores
on Bayley's Scales of Infant Development at age 3 years compared with control chil-
dren (Humphrey et al. 1998). It remains unknown if the mechanism was through
a reduction in severe morbidity or by some direct effect of vitamin A. In the sec-
ond study, Bangladeshi 3 year olds given vitamin A supplements at birth, did not
show developmental benefits compared with control children (van Dillen et al. 1996).
These findings suggest that vitamin A deficiency probably has only small, direct
negative effects on young children's development.
vItAmIn b
12
Several studies have shown links between vitamin B
12
deficiency and poor cogni-
tive functioning among the elderly, including dementia and neurocognitive defi-
cits. Among children, there have been only a few cross-sectional reports. The
mechanism linking B
12
deficiency may be through changes in neuroanatomy or
