ORIGINAL

Niger J Paed 2013; 40 (3): 243 –247

Ibekwe MU

Ibekwe RC

Correlation between serum zinc

level and height of adolescent school

girls in a Nigerian community

DOI:http://dx.doi.org/10.4314/njp.v40i3,8

Accepted: 1st December 2012

Abstract Background: This study

aims to asses the nutritional status

among adolescent school girls

using their serum zinc levels and

to correlate it with their height.

Method: This is a cross-sectional

study of adolescent girls attending

public secondary schools in

Oshimili local govt. area of Delta

state in Midwestern Nigeria.

mean serum zinc level of urban

girls (11.05±4.66µmol/l) was sig-

nificantly lower than that of rural

girls (15.54±6.31µmol/l)

Ibekwe MU

(

)

Department of Paediatrics

Ebonyi State University Teaching

Hospital, Abakaliki, Ebonyi State

Nigeria

Email: ugochiamadife@yahoo.com

Tel: +23480-33423291

(p = .009).

There was no correlation between

the mean serum zinc levels with

height SDS (p=0.28) and the BMI

SDS (p=0.69).

Conclusion: Majority of the ado-

lescent girls in Oshimili local Gov-

ernment Area of Delta State Mid

western Nigeria have low serum

zinc level when compared to

threshold value, and there was no

correlation of serum zinc with

their height SDS or BMI SDS.

Ibekwe RC

Department of Paediatrics

University of Nigeria Teaching Hopital

Enugu Nigeria

Results: The mean serum zinc

level of the total population was

1

(

3.30mmol/l±5.82. Majority

58.3%) of the girls failed to at-

tain the threshold value of

0.71mmol/l of serum zinc. The

mean height of the population was

55.4cm with Standard Deviation

1

Scores (SDS) score of -0.64±0.48,

Key Words: Adolescent girls,

Zinc level, Height, BMI ,

Correlation.

while the mean Body Mass Index

2

(

BMI) was 19.1kg/m ±2.91 with

an SDS score of -0.54±0.47. The

4

Introduction

logical role as an activator in bone formation . Specifi-

cally it enhances the anabolic effect of Insulin-like

growth factor 1( IGF-I) which is a major medi_,a₅tor of

Adolescence is a period of heightened nutritional re-

quirement where a growing individual is passing

through childhood to full adulthood . Because zinc has

been recognized to be essential for skeletal and muscular

growth as well as for sexual maturation, it’s need in-

creases during adolescent growth spurt . Girls who fail

to attain their full growth potential and who are mal-

nourished are at risk of having low birth weight babies

and obstetric complications. The need for zinc increases

during adolescent growth spurt. The essentiality of zinc

in humans was noted dramatically in the 1960s by a syn-

drome of growth retardation and arrested sexual matura-

4

growth hormone stimulated somatic growth . Zinc

1

supplementation has been fo₆u_-₁n₀ d to improve the linear

growth of stunted children .

In general the anabolic

effect of IGF-I in osteoblastic MC3T3-EI cells is en-

hanced through modulation by zinc. The increase in

growth velocity resulting from zinc supplementation

was found to be₁ associated with increased plasma IGF-1

2

1

concentrations The total body content of zinc is esti-

4

mated to be 2g. however the total daily requirement of

zinc in adolescent girls according to WHO expert panel

is 107-184 unit (7-12mg) . The recommended dietary

allowance (RDA) in adolescent girls is 11mg/day .

4

3

5

tion in eight adolescent boys in the Middle East . It was

noted that this syndrome could be reversed by dietary

supplementation with zinc. Average serum zinc status of

a group of adolescent can give an average level of serum

zinc in a locality.

Though there are no conventional store for zinc but

skeletal muscle account for 60%, bone account for 30%

4

,

and only 1% is found in plasma . The best dietary

sources of zinc are gener_,₁a₂lly animal products such as

5

meat, seafood, and milk . Although vegetable based

The interest on zinc on growth was initiated when Rona-

ghy in Iran demonstrated that stimulation of growth of

pre pubertal school boys could be brought about by sup-

plementation with zinc. Zinc is a co-enzyme in major

metabolic pathways and has been shown to play physio-

diet may contain zinc but it’s biological usefulness is

impair₄e_,₁d₃because of high fiber content found in vege-

tables Zinc is absorbed from the jejenum and it’s ab-

sorption is controlled by a homeostatic mechanism in

3

2

the intestine. Absorption of zinc is inhibited by the

2

44

1

7

presence of phytates and fiber in the diet that bind to

zinc .

size. Therefore a minimum sample size of 1067 girls

was required in the 8 selected schools. Permission to

carry out the research in the school was obtained from

the State Ministry of Education, and also approval of the

study protocol was obtained from the ethical committee

of the University of Benin Teaching Hospital, Benin.

The purpose and description of the study was explained

to their parents by a hand bill distributed through the

selected girls and informed consent was obtained from

their parents.

4

Zinc status can be assessed by measurement of zinc in

plasma, erythrocytes, neutrophils, lymphocytes, and

hair A single serum zinc estimation may not show a

4

long term status of zinc. However average serum zinc

status of a group of adolescents can give an average

1

3

level of serum zinc in a locality . Therefore Serum zinc

estimation is used in this study because it is cheap, less

cumbersome and can be performed with a relatively

simple technique using Atomic absorption spectropho-

tometer (AAS). The National Center for Health Statis-

tics and Nutrition Examination Survey (NHANES) used

serum zinc level below 10.71m₁₄m_,₁₅ol/l as a cut off value

as indicative of zinc deficiency

Sampling frame was obtained by complete listing of the

students’ name, sex and age in all classes of the schools

selected using the school register. With this sampling

frame, the students were further arranged by the age

cohorts in each schools as follows 10 -< 11, 11 - < 12,

1

2 - < 13,------- 19 - < 20. The sample size for each one

Since it has been established that adequate nutrition in

girls is essential for maternal health and prevention of

obstetric complications, therefore this study was done to

assess their nutritional status using serum zinc as a tool.

The micronutrient zinc and anthropometric parameters

including Height standard deviation score (Height SDS)

and Body Mass Index standard deviation score (BMI

SDS) were measured. Weight SDS was not used be-

cause the WHO anthro version 3.2.2 does not have

weight standard deviation values for children older than

year segment in each school was derived using the same

formula for the calculation of sample size. Thus a strati-

fied cluster (multistage) sampling technique was em-

ployed in the final subjects’ selection.

A proportion of 1/10 of these for each school was stud-

ied for zinc to attain the population coverage for the

study of micronutrient. A total of 151 girls were selected

for analysis of serum zinc. Using a pre-tested health and

life style questionnaire each recruited participant was

interviewed. General examinations of the girls were

done by the authors paying particular attention to pallor,

oral hygiene, skin conditions and musculoskeletal sys-

tems. The randomly selected girls had no obvious physi-

cal defect or evidence of chronic illnesses

1

0 years which formed the subjects of this study.

Subjects and methods

The study was carried out in the communities of

Oshimili North and South Local Government Areas

Anthropometry

(

LGA) of Delta State, Nigeria. Oshimili LGAs were

Height measurements without shoes on as described by

1

8

chosen because they represent both urban and rural set-

tings that were readily accessible. The definition of rural

and urban has₆ been predetermined by the Federal office

Janes work were done using a field wooden minimeter

attached to a straight wall calibrated to the nearest

0.5cm. A block was lowered in contact with the ruler to

touch the head of the subject being measured who was

standing erect with heels, buttocks and head touching

the wall. The heels were together and the feet at an angle

1

of statistics. Oshimili has a projected population of

1

43679 and is located on the West Bank of River Niger.

6

It shares borders with Ogwashiuku and Onitsha. The

1

o

inhabitants are made up of both indigenous population

and settlers from neighboring Eastern towns across the

Niger. Their chief occupation is fishing. There are 15

public secondary schools in both LGAs. The survey

involved adolescent girls aged 10-19 years in the 15

public secondary schools. Oshimili north LGA is pre-

dominantly urban and contain 8 schools while the re-

maining 7 schools are located in the Oshiimili south

LGA and are predominantly rural. Out of these 15

schools, 6 are girls’ schools only; 4 are boys’ schools

only while 5 are mixed schools. In this study girl only

schools and mixed schools were selected. To achieve a

reasonable measure of accuracy and increase the predic-

tive power of the study 53%(8) of the schools were se-

lected. Using a simple random sampling procedure, 8

schools were finally selected from the 15 schools in the

LGAs.

45 . The subject looked straight ahead. The heels were

close together before measurement was done. Body

weights without shoes, wearing only underwear were

measured using a SECA standing scale calibrated to the

nearest 100gm. All Height and Weight measurements

were in triplicate and the mean was recorded on each

occasion.

Serum Zinc Analysis

Serum zinc was analyzed₁u₉sing the atomic absorption

spectrophotometer (AAS), a Hitachi model 180 – 80

with a data processing unit model 180 – 0205. This was

done at the Biochemistry Department of the University

of Jos.

Data Analysis

The number of girls for the entire study was calculated

using the statistical formula for the calculation of sample

Data was entered into a computer using the software

SPSS version 16. The mean (x), standard deviation (SD)

2

45

and the Z-scores were determined using the WHO An-

thro version 3.2.2. Correlation between serum zinc and

the height SDS and BMI SDS were done using Pearson

correlation coefficient. Test of statistical significance

was done using the student’s t test and P values < 0.05 is

regarded as significant

Table 2: Mean serum Zinc levels of Urban and Rural subjects

Serum zinc

Rural

Urban

Total

p value

mmol/l

Mean

SD

15.54(34)

6.31

11.09 (117)

4.66

13.30 (151) .01

5.82

9

5%CI

14.03-20.17

8.70-11.09

10.37-12.85

P=<0.0001 Figure in bracket ( ) represent total number studied

Statistical test used= student t test)

(

Results

Fig 1 shows that there was no correlation between the

height SDS and serum zinc level of the subjects

(p=0.28), and fig 2 highlights that there was also no cor-

relation between the BMI SDS and serum zinc level

(p=0.69). Among the urban girls however there was a

correlation between their height SDS and their serum

zinc level (p = 0.03), there was also a correlation be-

tween their BMI SDS and serum zinc level ( p=0.04).

There was no correlation among the rural girls between

serum zinc level and either height SDS (p= 0.71) or

BMI SDS (p= 0.99).

A total of 1068 girls were selected for the study, of these

6

85(64%) and 383(36%) were from urban and rural ar-

eas respectively. Their mean age was 15.12yrs with a

range of 10-18 years. The mean height of the study

population was 155.4±10.74cm with a range of 122.5-

79.2cm. The mean BMI was 19.1kg/m2 ±2.91 with an

1

SDS score of -0.54±.47. The mean height of the rural

girls was 155.3±10.2cm with a range of 122.5-179.2cm.

The height range of urban girls was 129-179cm with a

mean of 155.5±11.28cm. There was no significant dif-

ference between the mean height of the urban and rural

girls (p=0.90).

Fig 1

The height SDS was -0.64±0.48 while the BMI SDS

was -0.54±0.47. There was no difference between the

height SDS of urban girls -0.64 ± 0.45 with that of rural

girls -0.65 ± 0.51(t=0.06, p=0.95). The BMI SDS of

urban girls -0.51± 0.52 was also not different from those

of rural girls -0.57± 0.42 (t= 0.57, p= 0.57).

Table 1 shows the baseline characteristics of the sub-

jects. There was no significant difference in age, weight,

height, BMI, height SDS and BMI SDS between the

girls in urban and rural areas.

Table1: Baseline characteristics of study subjects

Urban

Rural

P-value

Fig 2

Mean age (yrs)

14.87

15.51

Mean Height (cm)

Mean weight (kg)

Mean BMI (kg/m )

Height SDS

BMI SDS

155.5±11.28 155.3±10.2

0.90

0.64

0.80

0.95

0.57

46.1±11.33

19.1±2.91

-0.64± 0.45

-0.51±0.52

45.2±9.84

18.84±2.26

-0.65±0.51

-0.57±0.42

2

(p = <0.05 is statistically significant)

(Statistical test used= student t test)

Table 2 highlights the mean serum zinc levels of the

urban and rural girls studied. One hundred and fifty one

(

15.6%) girls were analyzed for serum zinc level. The

mean serum zinc level of the total population was

3.30µmol/l± 5.82. The urban girls had a mean serum

1

zinc level of 11.05±4.66µmol/l while the mean serum

zinc level for rural girls was 15.54±6.31µmol/l. The

mean serum zinc level of the urban girls was signifi-

cantly lower than that of the rural girls. (t= -2.75, p

Discussion

In this study, the mean serum zinc was 13.30µmol/l with

a range of 2.52-43.2µmol/l was within normal range.

However, since as many as 58.3% of them failed to at-

tain the threshold value of 10.71µmpl/l, it is therefore a

direct pointer to the fact that the disaggregated data on

zinc (urban/rural) is a better reflection of the state of

=

0.01). The proportion of girls studied that did not attain

the threshold value of 10.71µmol/l was 58.3% (88), out

of which 89.8% (79) of them were from urban areas.

2

46

zinc in the local environment of the study.

lack of an age dependent variation in the zinc level of

the girls.

The great disparity between urban and rural mean serum

zinc could result from lower intake of zinc by the urban

community, especially since these rural girls were

mainly children of fishermen and thus have better assess

to fish protein which is rich in zinc. It is also possible

that the values of the rural girls may have been affected

by the low sample size. Although the dietary intakes of

these girls were not assessed the observed lower values

of zinc might be a direct reflection of their inter-current

intakes. It is also possible that these adolescent girls may

have high phytate intake in their diets. It has been re-

ported that serum zinc concen₃tration was inversely cor-

2

Mbofong and Atimo discovered that the average daily

dietary zinc intake of Nigerians was generally low and

demanded increased intake in childhood, adolescence

and pregnancy. This may explain the low serum zinc

level in majority of the girls studied. Since zinc is found

in animal products such as meat and fish, and if these

girls do not consume adequate animal protein or are

consuming large quantities of phytate containing foods

in the presence of repeated infections and infestations;

these may account for the observed deficiency in zinc.

1

related with dietary phytate. Adolescent females are

vulnerable to deficiency of zinc. This is because of the

high requirement for growth, expanding blood volume

and sexual maturation. It is also postulated that adoles-

cents in Nigeria are under constant exposure and re-

peated attacks of malaria and other infection as a result

will have higher demand for zinc. Zinc supplementation

in childhood has also been shown to reduce infection

The finding from this study is limited by the fact that it

is not a longitudinal study and it was therefore not possi-

ble to incorporate increments and velocities of these

girls growth over a time period. The other notable limi-

tation is that serum zinc levels were assessed and this

does not necessarily correlate to total body zinc. It is

therefore recommended that a longitudinal study on the

relationship between dietary zinc intakes and

7

rates such as seen in malaria infections. This postulate

might explain the observed low values of serum zinc in

more than half of the study population.

anthropometry could have a wider clinical application.

2

0

Nakamura and Nishiyama studied 21 prepubertal short

Japanese children (11 boys) and found that they had

very low serum zinc level of 9.9µmol/l. This boys

gained height with zinc supplementation thus providing

the basis for the direct effect of hypozincaemia on

growth and puberty. This effect of hypozincaemia was

however not manifest in this study; the rural girls with

higher mean serum zinc level had lower height values,

though this difference was not statistically significant

Conclusion

majority of the adolescent girls in Oshimili local Gov-

ernment area of Delta State, Mid western Nigeria had

low serum zinc level when compared to threshold value.

There was however no correlation of serum zinc level

with their height SDS or BMI SDS. It is therefore rec-

ommended that there is need for nutritional intervention

to augment zinc intake of adolescent girls in the area

using public health education and school food supple-

mentations.

There was no correlation between the heights SDS of

these adolescents and their serum zinc. This lack of rela-

2

1

tionship was also observed by Michealson . The reason

for this is not very clear, since there is a correlation be-

tween the heights SDS of urban girls with their serum

zinc level. The absence of correlation can also imply the

Conflict of interest: None

Funding: None

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