Daily iron intake and BMI for age but not for daily tannin intake increase hemoglobin levels in young females at Karanganyar Regency, Central Java, Indonesia

Liyana Ilmiyati; Dono Indarto; Brian Wasita

doi:10.3897/folmed.64.e64593

Abstract

Introduction: Prevalence of anemia among young women in Indonesia has been seen to increase in the last five years. This situation indicates that this nutritional disorder looks like an iceberg phenomenon. Daily consumption of vegetables containing foods is recommended for prevention of non-communicable diseases including anemia. These foods contain not only ferric ions but also other natural compounds.

Aim: To analyse the relationship of daily intake of micronutrients and polyphenols with hemoglobin levels in young females.

Materials and methods: This cross-sectional study recruited 117 young females who studied in six senior high schools in Karanganyar Regency, Central Java; they were selected using a purposive sampling. Data of micronutrients and polyphenols intake were collected using the Semi Quantitative-Food Frequency questionnaire. Blood samples from lower arm veins were used for hemoglobin measurements in a hematology analyser. The collected data were analysed using the Rank Spearman and multiple regression linear tests to evaluate the relationship of micronutrients and polyphenols intake with the hemoglobin levels.

Results: The prevalence of anemia was 17.1% among 20/117 young females. Higher dietary intake of iron (b=0.043; p<0.001) and higher BMI for age (b=0.246; p=0.025) increased the Hb levels while higher dietary intake of tannin (b=−0.003; p=0.009) decreased them.

Conclusions: Dietary intake of iron and BMI for age are related to the hemoglobin levels but tannin intake is inversely related to these levels in young females. Higher iron intake from vegetable resources should be taken into account for anemia reduction in young females due to the presence of tannins.

Keywords

anemia, micronutrients, polyphenols, young females

Introduction

Anemia remains a nutritional problem around the world, which looks like an iceberg phenomenon and is primarily caused by iron deficiency.^[1] In 2018, the morbidity rate of anemia in Indonesia increased by 48.9%, which mostly affectеd female adolescents and young adults (15-24 years old).^[2] For a long term period, anemia in young adults who get pregnant will have bad impacts on their health and fetus such as preeclampsia, bleeding, low birth weight, small-for-gestational-age fetus, and premature birth.^[3,4]

Daily vegetable consumption is recommended for prevention of non-communicable diseases (NCDs)^[5] including anemia. Vegetables are not only an iron source but also other natural sources that play an important role in iron metabolism such as vitamin A, vitamin E, and polyphenols.^[6,7] Vitamin A can increase iron absorption in the small intestine by mobilization of iron-containing ferritin to all body tissues.^[8] Apart from vitamin A, daily intake of vitamin E functions physiologically as an exogenous antioxidant and oxidant scavenger in red blood cells for preventing lipid peroxidation by free radicals in cell membranes and organelles.^[9,10] A randomized control trial conducted in Colorado showed that serum vitamin E and iron consumptions can increase serum ferritin levels, back to normal condition.‌^[11^] Beside micronutrients, vegetables also have a variety of polyphenols like tannins and phytate that are widely distributed in all parts of vegetables. Tannins interact with iron to make complex compounds which reduce iron availability and are with low absorption in the small intestine.^[12] Two other chemical compounds (phytate and oxalic acids) are also recognized as natural inhibitors of iron absorption. From epidemiological and experimental studies, the roles of those micronutrients and polyphenols in anemia disorder have indicated contradictory results.^[13,14]

Aim

This study aimed to assess the relationship of dietary intake of micronutrients and polyphenols by measuring the Hb levels in young females.

Materials and methods

Research participants

One hundred and seventeen young females who studied at high and vocational schools in Colomadu, Jumapolo and Matesih districts participated in this study and were selected using a purposive sampling. We recruited young females who were in grade X and XI from those schools, aged 14-18 years old and lived in those districts at least 6 months whilst we excluded those who had menstruation and had blood disorders such as thalassemia, worm infection and malaria. The study protocol was approved by the Health Research Ethic Committee of Dr. Moewardi General Hospital, Surakarta (No. 102/I/HREC/2020) and all of study participants signed an informed consent before the research began.

Study design and data collection

The present study has a cross-sectional design; it was conducted from February to April, 2020. The sample size was calculated using a formula based on the prevalence of anemia in Karanganyar regency (data not shown). Venous blood samples of research participants were used to determine the Hb levels by using a hematology analyser at the Clinical Laboratories in Surakarta City, Jumapolo, or Matesih Community Health Centres. Young women with Hb levels higher or equal to 12 g/dL were categorized as having no anemia.^[15] Nutritional data of micronutrients, tannin, phytate, oxalate, and confounding factors such as protein and iron were collected using the semi-quantitative food frequency questionnaire (SQ FFQ). Calculated values of vitamin A, vitamin E, iron, and protein intake were compared with nutrient intake values of Indonesian Recommended Dietary Allowance (RDA) (data not shown). Furthermore, the body mass index (BMI) for age was determined using the WHO Z-score table and then the participants were classified as either thin (−3 SD to <−2 SD), normal (−2 SD to +1 SD), overweight (+1 SD to +2 SD), or obese (>+2 SD) according to their respective index.

Statistical analysis

SPSS v. 21 was used to analyse all collected data. Mean ± standard deviation (SD) represented numeric data whereas frequency and percentage represented categorical data. Before performing the correlation test, data normality was assessed using the Kolmogorov-Smirnov test. Independent Student t and Mann-Whitney tests were used to compare the non-anemia with anemia groups (Tables 1, 2) whilst the Rank Spearman test was used to examine the correlations of independent variables and confounding factors with Hb levels (Table 3). The multiple linear regression test was used to evaluate further correlations of those variables with Hb levels (Table 4). A p value less than 0.05 was considered statistically significant.

Results

Table 1 shows the general characteristics of research participants. Anemia was found in 17.1% (20/117) of the young women. The average of age, menstruation length, and BMI for age in non-anemic young females was slightly lower than that of anemic young females while non-anemic young females had a higher average of physical activity and parent income compared to anemic young females. However, the average BMI for age in both groups was normal weight although the non-anemia group had a significantly higher average BMI than the anemia group. In addition, parents income in the non-anemia group had an average close to the minimum wage in Karanganyar Regency (IDR 1.989 million).^[16]

Table 2 shows the average daily consumption of nutrients and polyphenols in the non-anemia and anemia groups. As can be seen, the average vitamin A, vitamin E, tannin, oxalate, phytate, and protein consumption was higher in the anemia group compared with the non-anemia group but a higher daily intake of Fe and vitamin C was observed in the non-anemia group. In addition, only the Fe daily intake reached significance (p<0.001).

To assess the independent correlation of all daily dietary intake and BMI for age with Hb levels, the Spearman test was performed. In general, all variables indicated positive correlations with Hb levels except for tannins, oxalates, and phytates (Table 3). Furthermore, Fe and vitamin C daily intake had a significant correlation with Hb levels and the higher correlation was Fe daily intake (r=0.40; p<0.001).

The next statistical analysis used the multiple linear regression test for evaluating all variables, which together influenced Hb levels in young females (Table 4). Fe daily intake was significantly related to Hb level (b=0.043; p<0.001) after adjustment with confounding factors. However, this relationship was weaker than the correlation between BMI for age as the confounding factor and Hb level (b=0.246; p=0.025). This study also showed that there was a negative correlation of tannin daily intake with the Hb levels which reached significance (b=−0.003; p=0.009).

Table 1.

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Baseline characteristics of the young females who participated in this study

Variable	Non-anemia (n=97)		Anemia (n=20)
Variable	Min-Max	Mean ± SD	Min-Max	Mean ± SD	P
Age (years)	14-18	15.7±0.74	15-17	16±0.64	0.147
Menstruation (days)	4-9	6.27±1.1	4-9	6.65±1.18	0.139
Physical activity (METs)	328.5-5992	1674.2±1423.1	500-2933	995±701.5	0.161
Parents income (IDR million)	0.45-5	1.9314±1.179	0.5-3	1.545±0.66	0.343
BMI for age (z-score)**	-2.67 -2.69	-0.07±1.16	-2.1-2.5	-1.04±1.27	0.001**

Table 2.

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The average of daily dietary intake in anemic and non anemic young females

Variable	Non Anemia (n=97)		Anemia (n=20)
Variable	Min-Max	Mean ± SD	Min-Max	Mean ± SD	P
Daily Food Intake
Fe (mg/day)**	4.11-85.96	26.06±14.24	4.92-42.12	13.05±8.84	<0.001*
Vitamin A (RE/day)	114.54-1.719.6	628.8±396.5	100.6-1,492.2	652.8±353	0.393
Vitamin E (mcg/day)	0.76-80.43	12.84±12.42	2.01-51.94	12.97±12.01	0.257
Tannin (mg/day)	107.03-489.8	205.5±84.9	110.8-896.1	268±174.9	0.092
Oxalate (g/day)	0.01-2.81	0.48±0.15	0.07-6.83	2±0.813	0.379
Phytate (mg/day)	23.62-1,708.8	364.4±346.4	10.08-1.364.84	394.38±347.8	0.558
Confounding factor
Protein (g/day)	20.1-277.9	83.8±51.8	11.2-337.9	84±75.7	0.664
Vitamin C (mg/day)**	37.02-385.69	189.9±97.7	52.29-342.34	167.5±88.9	0.334

Table 3.

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The relationship of independent variables and confounding factors with Hb levels

Variable	r	P
Daily Food Intake
Fe (mg/day)	0.40	<0.001*
Vitamin A (RE/day)	0.01	0.289
Vitamin E (mcg/day)	0.01	0.900
Tannin (mg/day)	−0.11	0.234
Oxalate (g/day)	−0.07	0.442
Phytate (mg/day)	−0.10	0.273
Confounding factor
Protein intake (g/day)	0.07	0.45
Vitamin C (mg/day)	0.20	0.033
BMI for age (z-score)	0.15	0.094

Table 4.

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Multivariate analysis of independent variables and confounding factors with Hb levels

Variable	b	T	p	95% CI	β
Constant	12.419	28.117	0.000	11.54-13.29
Fe intake (mg/day)	0.043	4.482	<0.001*	0.024-0.062	0.381
Tannin intake (mg/day)	-0.003	-2.673	0.009*	-0.006-0.001	-0.230
Vitamin C (mg/day)	0.002	1.484	0.141	-0.001-0.005	0.131
BMI for age (z-score)	0.246	2.278	0.025*	0.032-0.46	0.188

Discussion

In this study, we found that 17.1% of the young females in Karanganyar regency had anemia. It clearly indicated that daily Fe and tannin intake influenced the Hb levels with opposite correlation and BMI for age also influenced the Hb levels. The results in this study are in line with a previous study which found a significant relationship between iron intake and adolescent Hb levels.^[17] Theoretically, iron is a major component of red blood cell formation with nearly two-thirds of it found in hemoglobin.^[18] This study also shows that there is a negative correlation of tannin daily intake with Hb levels. This result indicated that the increased tannin consumption was followed by a decrease of the Hb levels in the young women in the study. This is consistent with the theory that tannins interact with iron to make complex compounds which reduce iron availability resulting in its low absorption in the small intestine. All vegetables contain different tannin levels which belong to polyphenols. The inhibitory effect of polyphenols on iron absorption has been widely reported^[12] but the reduction in iron absorption depends on each structure of polyphenols.^[19] Moreover, vitamin C daily intake in this study had a positive correlation with the Hb level but it failed to reach significance. This is probably due to the adequate daily intake of vitamin C in young females in the anemia and non-anemia groups but unable to reduce the inhibitory effect of tannins derived from vegetables and fruits.^[20] However, the important role of phytate and oxalate as Fe inhibitors can be ignored in this study since their correlations were weak and not significant to Hb levels.

The Hb levels in young females were also influenced by BMI for age (z-score). Our data indicated that the mean BMI for age of young females in the non-anemia group was higher than the mean BMI for age of young females in the anemia group (Table 1). It means that young females in the non-anemia group had better nutritional status which denotes the balance state of nutrient intake, nutrient requirement, and human body metabolism. Altogether, Fe, tannin daily intake, and BMI for age in young females in Karanganyar regency significantly influence the Hb levels by 24.1%.

Conclusions

Daily iron and tannin consumptions are differently related to Hb level in young females at Karanganyar Regency. Furthermore, BMI for age has a stronger relationship to Hb levels than daily iron and tannin consumptions although this factor is not the main research variable. These findings confirm that daily iron intake plays a vital role for maintaining the hematological status of young females. However, we used just a limited number of research participants to generate these data, which do not represent general Indonesian population. In addition, further studies are needed using a combination of food questionnaire, food records, and biological markers to investigate all factors that contribute to Hb production.

Acknowledgments

The authors would like to thank the principals and their staff of higher vocational schools in Colomadu, Jumapolo and Matesih districts for giving permission and the Health Laboratories in Surakarta City, Jumapolo, or Matesih Community Health Center for the hemoglobin levels assessment.

Funding

This study was partially funded by the Indonesian Ministry of Research and Technology in 2020 (065/SP2H/LT/DRPM/2020).

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