Agriculture Reference
In-Depth Information
as ferric salts. Thus, it is likely that iron deficiency is very common in young children
and detrimental to their health and development (see Chapters 11 and 12).
Iron toxicity is usually considered only from iron overdose, as in toddlers con-
suming their mother's iron supplements or patients on excess oral or parenteral iron
or having numerous blood transfusions. Iron absorption is normally highly con-
trolled at the intestinal level. However, hemochromatosis is an inherited disorder
in which iron absorption is increased, and the resultant excess stored iron causes
organ damage, particularly in the liver, pancreas, testis and heart. Surprisingly, it
was found that plasma ferritin, a measure of iron stores, was very high in severely
malnourished children, especially those with edematous malnutrition and those who
died (Srikantia 1958). This could be due to an acute-phase response in which iron
is normally sequestered in the liver. However, there is little evidence of such a host
response to infection in these ill children. The high plasma ferritin is more likely to
reflect genuine iron overload. This implies the risk of “free” iron available for both
the growth of pathogens and to act as a prooxidant, possibly responsible for general-
ized cell damage, via lipid peroxidation of membranes (Golden and Ramdath 1987).
Therefore, iron therapy is contraindicated in the early management of severely mal-
nourished children (World Health Organization [WHO] 1999a).
i
r o n
s
t a t u s
Anemia prevalence is not a good measure of the extent of the problem. The same
is true for plasma iron concentration. This is affected, more often than not, by the
presence of an acute-phase response, usually to invasion by bacteria, viruses, and
the like as described. As part of this, circulating iron is bound to proteins within the
liver so plasma iron decreases. Iron stores, mainly in the liver, can be estimated indi-
rectly by measuring plasma ferritin concentration. However, this increases during an
acute-phase response. Thus, a “normal” value may have been a low value before the
child developed pneumonia, for example. Finally, another indirect measure of iron
status is the plasma concentration of transferrin receptor. An increase in this protein
implies that the iron supply for hemoglobin synthesis in the bone marrow is deficient.
It is supposed to be independent of an acute-phase response, but this is unlikely.
In conclusion, iron status is probably best assessed today by measuring iron stores
(plasma ferritin) when there is no evidence of an acute-phase response.
zInc
Zinc is half as abundant as iron in the body. Whereas iron is required for a few pro-
teins, zinc is ubiquitous: It is required for the structure or function of at least 200
metalloenzymes, within cytoplasm, nucleus, and membranes (Hallberg et al. 2000).
Without zinc, neither cell hyperplasia, requiring DNA synthesis, nor hypertrophy,
requiring protein synthesis, can occur.
When a zinc-deficient diet is fed to rats, they experience fluctuating anorexia,
with spells of reasonable intake separated by spells of very poor intake; their growth
is severely restricted. When such a diet is force-fed to rats, they die within only a
few days.
