Has been known of for 40 years but ignored by global
health organisations
Although it has been known for more than six decades that zinc is essential
for the growth of micro-organisms, plants, andanimals, until 1961 it
was believed that zinc deficiency in humanscould never occur. It is
now clear that nutritional deficiencyof zinc is widely prevalent and
its morbidities are severe. Thisarticle describes the history of the
study of zinc deficiencyfrom a single case report in 1961 to its
currentstate.
In 1958, a 21 year old male patient in the Iranian city of Shiraz presented
with dwarfism, hypogonadism, hepatosplenomegaly,rough and dry skin,
mental lethargy, geophagia, and iron deficiencyanaemia.1
This patient had an unusual diet. His intake of animalprotein was
negligible, and he ate only unleavened bread. In addition,he
consumed 0.5 kg of clay daily. His total intake of caloriesand
protein (cereal) was adequate, and except for iron deficiencyno
other deficiency in micronutrients was documented consistently.In
the following three months 10 more patients with a similarillness
were seen in the same hospital. The growth retardationand testicular
hypofunction in all these patients could not beexplained on the
basis of iron deficiencythese
manifestationsare not observed even in iron deficient animals. In
animals, amongthe transitional elements known to have adverse
effects on healthdue to deficiency (Cr, Mn,Co,Cu, and Zn), only zinc
deficiencywas known to cause growth retardation and testicularhypofunction.
I speculated that some dietary factors responsible for the decreased
availability of iron in geophagic patients might alsohave decreased
the availability of zinc.1 Later it became knownthat phytate in cereals markedly impairs the absorption of zinc
and also iron.2 With a well balanced animal protein
diet andadministration of iron, all the clinical features in the
Iranianpatients werecorrected.
I saw similar patients in Egypt. The evidence for zinc deficiency in these
patients was that their concentrations of zincin plasma, red blood
cells, hair, and a 24 hour urine sample weredecreased compared with
controls; 65Zn studies showed that the plasma disappearance curve of
zincwas more rapid and the 24 hour exchangeable pool was decreased.Further, the rate of growth in patients who received zinc supplements(average 12.7 cm per year) was much greater compared with those
who received iron instead or only an adequate animal protein diet. 34 Gonadal changes were also
reversed by zinc supplementation only.Patients who had iron
supplementation corrected their anaemia,but no effect was noted on
growth or gonads. In 1973, Barnes andMoynahan noted that
acrodermatitis enteropathica, a fatal geneticdisorder, was cured by
supplementation with zinc.5 It is now
known that patients with acrodermatitis enteropathica do not absorb
dietary zincnormally.
The discovery that zinc is essential for humans made a notable impact. In
1974 the Food and Nutrition Board of the US NationalAcademy of
Sciences made a landmark decision, to declare zincan essential
nutrient and establish recommended dietary allowancesfor humans.
Later, including zinc in total parenteral nutritionfluids was made
mandatory, which undoubtedly saved many lives.Dietary zinc
deficiency is very prevalent in the developing world(affecting
nearly two billion people), where mainly cereals areconsumed by the
population. A meta-analysis of 33 prospectiveintervention trials of
zinc supplementation and its effects onchildren's growth in many
countries showed that zinc supplementationalone had a statistically
significant effect on linear growthand body weight gain, indicating
that other deficiencies thatmay have been present were not
responsible for growth retardation.6
Zinc supplementation has been shown to improve neuropsychological
functions in Chinese children with zinc deficiency.7
It reducesthe incidence and duration of acute and chronic diarrhoea
andacute lower respiratory tract infections in children in
developingcountries, resulting in decreased mortality.8
Zinc deficiencyin pregnant women causes abnormal labour, retarded
fetal growth,and fetal abnormalities.9
The immunological effects of zinc deficiency during the early 1960s were not
known, although I knew that patients with zincdeficiency in the
Middle East died of infection before the ageof 25 (personal
observation). It has now been shown that in peoplewith zinc
deficiency, activity of serum thymulin (a thymus specifichormone
involved in T cell function) is decreased, an imbalancebetween T
helper cell (Th1) and Th2 function develops, and lyticactivity of
natural killer cells and the percentage of precursorsof cytolytic T
cells is decreased. 1011
Zinc deficiency has now been recognised to be associated with many diseasesfor
example, malabsorption syndrome, chronic liverdisease, chronic renal
disease, sickle cell disease, diabetes,malignancy, and other chronic
illnesses.9 In these conditions,
deficiencies of other micronutrients such as vitamins and othertrace
elements may also be associated. It should be emphasisedthat
nutritional zinc deficiency in the developing countries doesnot
occur inisolation.
Recently the National Institutes of Health's Eye Institute conducted a large
double blind clinical trial including 3640 elderlyparticipants,
which showed that antioxidants and zinc supplementsdelayed
progression of age related macular degeneration and reducedthe risk
of loss of vision.12 Zinc deficiency is also
commonin elderly people.9
Zinc decreases the copper burden in humans; as such it has been used
effectively to treat Wilson's disease.9 In
therapeuticdoses, zinc has been shown to be beneficial in the
treatment ofhepatic encephalopathy, sickle cell disease, and the
commoncold.
More than 300 catalytically active zinc metalloproteins and more than
2000 zinc dependent transcription factors involved ingene expression
of various proteins have been recognised. 1314
We have recently shown in cell culture studies that zinc activates nuclear
factor-kappa B in T helper cells and in zinc deficiencybinding of
nuclear factor-kappa B to deoxyribonucleic acid isdecreased, leading
to decreased gene expression of interleukin2 and its production.15
The problem has been known for 40 years and a solution is still outstanding.
Despite all the evidence practically no attentionhas been given to
the problem of zinc deficiency by the world'sorganisations. Growth
retardation, increased susceptibility toinfectious and cognitive
impairment are common in developing countrieswhere nutritional
deficiency of zinc is also prevalent. Thus acorrection of zinc
deficiency is likely to have a great impacton the health of a large
population in the developing world andit is imperative that the
World Health Organization must includethis problem in its toppriorities.
Ananda S Prasad, distinguished professor of medicine.
Wayne State University School of Medicine, Internal Medicine, University
Health Center 5-C, 4201 St Antoine, Detroit, MI 48201 USA (prasada@karmanos.org)
Prasad AS, Halsted JA, Nadimi M. Syndrome of iron
deficiency anemia, hepatosplenomegaly, hypogonadism, dwarfism and geophagia.
Am J Med 1961; 31: 532-546[ISI].
Prasad AS, Miale A, Farid Z, Sandstead HH, Schulert AR.
Zinc metabolism in patients with the syndrome of iron deficiency anemia,
hypogonadism, and dwarfism. J Lab Clin Med 1963; 61: 537-549[ISI].
Sandstead HH, Prasad AS, Schulert AR, Farid Z, Miale A,
Bassily S, et al. Human zinc deficiency, endocrine manifestations and
response to treatment. Am J Clin Nutr 1967; 20: 422-442[ISI][Medline].
Brown KH, Peerson JM, Rivera J, Allen LH. Effect of
supplemental zinc on the growth and serum zinc concentrations of prepubertal
children: a meta-analysis of randomized controlled trials. Am J Clin Nutr
2002; 75: 1062-1071[Abstract/Free
Full Text].
Sandstead HH, Penland JG, Alcock NW, Dayal HH, Chen XC, Li
JS, et al. Effects of repletion with zinc and other micronutrients on
neuropsychologic performance and growth of Chinese children. Am J Clin
Nutr 1998; 68(2 suppl): S470-S475[Abstract].
Sazawal S, Black RE, Bhan MK, Bhandari N, Sinha A, Jalla S.
Zinc supplementation in young children with acute diarrhea in India. N
Eng J Med 1995; 338: 839-844.
Beck FWJ, Prasad AS, Kaplan J, Fitzgerald JT, Brewer GJ.
Changes in cytokines production and T cell subpopulations in experimentally
induced zinc-deficient humans. Am J Physiol 1997; 272: E1002-E1007[ISI][Medline].
Age-Related Eye Disease Study Research Group (AREDS) Report
No. 8. A randomized, placebo-controlled, clinical trial of high-dose
supplementation with vitamins C and E, beta-carotene, and zinc for
age-related macular degeneration and vision loss. Arch Ophthalmol
2001; 119: 1417-1436[CrossRef][ISI].
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