CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 5, September/October 2011
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AFRICA
iron need greater than that of boys.
29
The present study consisted
of men and women across all age groups, which makes it less
comparable to the Iranian study. Studies have also reported
appreciable differences in the prevalence of obesity among
different ethnic groups.
30,31
Chambers
et al
.
32
reported an inverse
relationship between body fat distribution and serum iron
concentrations in Hispanic women but not in white, African-
American or Asian women.
In the present study, a lower serum iron concentration in
the obese than the normal-weight and pre-obese women was
observed. Serum iron concentrations in the obese remained
significantly lower than in the pre-obese women after adjust-
ing for age and smoking. This is congruent with the findings
by Tussing-Humphreys,
33
who reported that the prevalence
of iron deficiency was higher in overweight girls. Moreover,
serum iron concentration was reported to decrease as BMI
increased in adolescent Iranian girls.
27
The National Health and
Nutrition Examination Survey I
34
reported that higher BMI was
significantly associated with lower serum iron concentrations in
women. Serum iron concentration is, however, not a sensitive
marker of iron status, due to diurnal changes.
35
An understanding of the link between fat deposition and ferri-
tin secretion may offer an explanation of some of these observa-
tions. During fat deposition, lipid biosynthesis increases, which
might lead to an increase in iron-induced lipid oxidation as a
result of the reactivity of intracellular iron with lipids. There is a
probability that ferritin levels are elevated to act as an iron cyto-
protective agent.
36
Therefore, increased ferritin concentrations
may be an adaptive mechanism to reduce iron-induced oxida-
tive stress, which could explain the positive correlation between
ferritin concentrations and anthropometric CVD risk factors.
Ferritin is an acute-phase reactant, which increases in concen-
tration during inflammation. Since obesity is considered an
inflammatory state,
37
it could serve as an additional explanation
for the positive association between ferritin concentrations and
anthropometric indicators. However, serum ferritin concen-
trations can be influenced by other inflammatory conditions
resulting from infection. A deficient iron store owing to greater
iron requirements in obese adults because of their larger blood
volume
38
has also been proposed to be the mechanism involved
in the iron deficiency–obesity association. Functional iron defi-
ciency can occur during inflammation (even when iron stores are
optimal) as a result of impairment of the normal physiological
systems for transport of iron to the target tissue.
10
It is not clear which precedes the other, obesity or iron defi-
ciency. Iron takes part in diverse physiological functions such
as transport of oxygen by haemoglobin and myoglobin, energy
metabolism by the haeme-containing proteins of the mitochon-
drial electron transport apparatus and the conversion of ribose to
deoxyribose nucleic acids by the iron-containing ribonucleotide
reductase, which is required for the propagation of genetic infor-
mation.
10
Given the critical dependence of body tissues on iron,
it is possible that its deficiency could result in accumulation of
fat in the body tissues. Impaired fat oxidation has been reported
to be a risk factor for excess weight gain in several populations
known to be susceptible to obesity.
39,40
Fat that is not oxidised
must be stored, which can result in increased fat deposition with
time. Iron deficiency has also been linked to problems with work
and exercise capacity among adults,
41
which may eventually lead
to a sedentary lifestyle and weight gain.
Lipid deposition allows efficient storage of maximal calories
in adipose tissue located beneath the skin (subcutaneous fat),
around internal organs (visceral fat) and in the yellow bone
marrow.
42
Subcutaneous fat tissue stores about 80% of all body
fat, and excess fat is stored in other storage tissues, such as the
intra-abdominal tissue when the subcutaneous tissue reaches a
threshold level.
43
Therefore, storage of excess fat in the central
region may be a signal for abnormal fat storage, which has adverse
health implications. It has been found that body fat distribution,
especially abdominal fat is more important than total body fat
in the aetiology of CVD.
44
William
et al
.
45
identified measure-
ments at or above the waist to be most associated with disease
risk for both genders. However, in the present study, 79% of
men and 60% of women were within the optimal cut-off point.
24
There is speculation that hepcidin, a peptide hormone
involved in the regulation of intracellular iron, may be involved
in the association of obesity and iron deficiency.
46
Hepcidin is an
acute-phase reactant that is stimulated in inflammation, includ-
ing obesity.
47
Moreover, recent discoveries indicated that adipo-
cytes are not just passive organs for fat storage, instead, they are
also endocrine organs which play regulatory roles in whole-body
physiology.
48
Increased secretion of hepcidin has been reported
to inhibit the release of non-haeme iron from macrophages.
49
It is
possible that increased expression of hepcidin in obese individu-
als interferes with iron absorption, thereby resulting in iron defi-
ciency. Unfortunately, hepcidin was not measured in the present
study as it might have helped to clarify the situation.
Gender has been reported to be one of the factors that influ-
ence serum ferritin concentrations.
50
A significant difference in
serum ferritin concentrations was demonstrated between men
and women in this study. Leggett
et al.
51
found that the pattern
of ferritin increase varied in men and women. Ferritin concentra-
tions in women, although increasing, remained low until after
menopause, whereas those of men continued to increase, reach-
ing a peak in their fourth decade, when iron stores are expected
to be stable following the growth period. This suggests that the
observed difference between men and women may be as a result
of physiological differences (i.e. menstruation and hormone
secretion) that affect iron storage. Moreover, the pattern of fat
distribution in men has been reported to differ from that in
women. Women usually show greater lower body fat distribu-
tion (gynoid) while men show more upper body fat distribution
(android).
42
The present study supports these findings as men had
significantly higher WC than women.
This study illustrates conclusively that a relationship exists
between some measures of iron status and certain anthropomet-
ric CVD risk markers, particularly ferritin concentrations and
WC or WHR. This implies that individuals who fell within the
positive iron-balance group, the at-risk group for iron overload,
may additionally be at a greater risk of developing CVD in this
particular population. However, due to the nature of the design
of this study, causality cannot be established.
Implication for health and research
Iron deficiency is the most common micronutrient deficiency
in the world
2
and it has been a priority for most countries when
addressing issues on health. South Africa is among the countries
with moderate iron deficiency.
52
The Department of Health in
South Africa is using an adapted form of UNICEF’s conceptual
