Unlocking the connection: hematological status, dietary iron intake and endurance in Indian female athletes
Article information
Abstract
[Purpose]
The United Nations Sustainable Development Goals (SDGs) aim to reduce the prevalence of anemia in women of reproductive age by 50% before 2030. However, negligible global change has been observed in the prevalence of anemia; therefore, achieving the SDG target for anemia reduction by 2030 may be challenging. Athletes are particularly susceptible to anemia owing to their poor diet and intense physical activity, which can significantly impact endurance levels. This study aimed to determine the correlation between hematological status and endurance in Indian female athletes. The frequency of iron-rich food consumption and dietary iron intake by the athletes was also identified.
[Methods]
In this cross-sectional observational study, 104 athletes aged 18–25, including 52 volleyball and 52 ball badminton players who were training in SRM institute of science and technology and Tamil Nadu physical education and sports university were assessed for hematological status using an automated hematological analyzer and endurance through Cooper's and plank tests. The results were statistically analyzed to compare the two groups of athletes and Spearman’s correlation coefficient was used to study the correlation between hematological status and endurance. A food frequency questionnaire focusing on iron-rich foods and 24 h dietary recall was used to evaluate dietary iron intake.
[Results]
Approximately 53.8% of the total group of athletes were anemic. The study confirmed a positive correlation between hematological status and cardiorespiratory endurance among volleyball athletes (r = 0.36) and all athletes (r = 0.22). Volleyball athletes demonstrated better endurance than did ball badminton athletes (p < 0.001) and non-anemic athletes exhibited superior endurance performance compared with that of anemic athletes. The consumption of iron-rich foods of athletes was inadequate.
[Conclusion]
Athletes need to consume a varied and nutritious iron-rich diet to maintain their hematological status and improve endurance.
INTRODUCTION
A direct relationship exists between micronutrient status and the performance level of athletes. However, this relationship is often not given due importance when compared with the macronutrient status of an athlete. An exponential growth has been observed in the number of women participating in various sports in recent years [1]; however, as several physiological and hormonal patterns are specific to females, these athletes are more prone to injuries and various health disorders compared with their male counterparts [2]. Female athletes tend to have lower hemoglobin levels than those of male athletes and non-athletic counterparts, a condition that is termed “sports anemia.” This could be due to factors, such as plasma volume expansion, hemodilution, increased iron loss, imbalanced diet, or poor iron absorption [3]. The hematological status of female athletes is significantly linked to their fitness levels. Reduced hemoglobin levels can lead to reduced oxygen-carrying capacity, which can result in reduced oxygen to the muscles during exercise, leading to hindered performance [4].
Iron supplementation in iron-depleted female athletes has been shown to improve iron status and energy efficiency [5]. To address the increasing training needs and optimize performance, female athletes need to maintain their hematological status in the optimal range by consuming a well-balanced, colorful diet that includes various foods rich in iron [6,7]. Endurance athletes are frequently reported to have a higher prevalence of iron deficiency owing to the predominant role of iron in aerobic pathways [8]. Although several studies have assessed the prevalence of anemia in adolescents, research on the prevalence of anemia in Indian female athletes remains limited, which necessitates the current study. Additionally, a huge gap in research exists regarding nutritional strategies for better performance in female athletes [9]. Sufficient evidence to establish a correlation between hematological status and endurance lacks, specifically in ball badminton and volleyball athletes, making this the first study to correlate and analyze their relationship with the dietary iron intake of Indian female athletes. Hence, this study aimed to analyze the relationships among hematological status, endurance performance, and dietary iron intake in female ball badminton and volleyball athletes in India.
METHODS
Study design
This cross-sectional observational study analyzed the hematological status,endurance, and dietary iron intake of female athletes in India. The study was conducted among female athletes training in SRM institute of science and technology and Tamil Nadu physical education and sports university situated in Chengalpattu district.
Study participants
This study included 104 healthy female athletes who were trained in volleyball (VB; n = 52) and ball badminton (BB; n = 52). VB and BB athletes were chosen because both are team sports with different intensities. The inclusion criteria were female athletes aged 18-25 years who trained for a minimum of 3-4 d per week for a minimum period of 90 min and were willing to participate in the study. The exclusion criteria were male athletes, female athletes aged < 18 years and > 25 years, athletes with major health complications, those consuming medications or supplements, pregnant and lactating athletes, and those who were unwilling to participate in the study.
Ethical considerations
This study was conducted with the ethical approval from institutional ethical committee of SRM institute of science and technology (Ref No. 8476/IEC/2022). Approval was also obtained from the Directors of Department of Physical Education, SRMIST and Tamil Nadu physical education and sports university , the respective managers and coaches of the athletes. All athletes were informed about the objectives of the study, the procedures involved, and the possible benefits of the study; written informed consent was obtained from each athlete.
Body composition assessment
The height and weight of the athletes were measured under laboratory conditions following the standard specifications of the International Society for the Advancement of Kinanthropometry (ISAK) using appropriate equipment and procedures. The standing height of the athletes was measured using an InBody BSM 170 stadiometer. The athletes were asked to stand on the stadiometer platform without shoes, arms at their sides, feet together, and head facing forward. The maximum distance between the stadiometer platform and head bar was noted on the digital display. The body weights of the athletes were measured using a calibrated weighing scale, barefoot, and with light clothing. Body mass index (BMI) was calculated using the following formula: BMI = Weight (kg)/height (m2). Subsequently, the WHO ASIAN BMI classification was used to categorize athletes as underweight, normal weight, overweight, or obese.
Biochemical assessment
Venous blood was collected from all athletes by a professional phlebotomist at the SRM Hospital and Research Centre after a 12 h fasting period. Ethylenediaminetetraacetic acid (EDTA) whole blood was used to measure hematological parameters, such as hemoglobin, mean corpuscular hemoglobin concentration (MCHC), hematocrit, mean corpuscular volume (MCV), red blood cell (RBC) count, white blood cell (WBC) count, and platelet blood count, which were determined using a Sysmex automated hematology analyzer and compared with the normal ranges: hemoglobin [12-14 g/dl] [10], platelet blood count (1,50,000-4,50,000/cumm), White Blood Cell count (4000-11000/cumm), Red Blood Cell count (3.8-4.8 milli/cumm), Mean Corpuscular Volume (83-101 fl), Mean Corpuscular Hemoglobin (27-32 pg), Mean Corpuscular Hemoglobin Concentration (31.5-34.5 g/dl) [11], and hematocrit (36%-46%).
Endurance assessment
Cardiorespiratory endurance
The Coopers 12 min walk/run test was used to measure cardiovascular endurance in female athletes. In this test, the athletes were allowed to warm up and were asked to run for 12 min on a 400 m track; the total number of laps and distance covered in 12 min was recorded. The athletes were instructed to push themselves as much as possible to run and not walk to cover the maximum distance. Markers were placed at set intervals to record the distance covered in meters. Using the distance covered in meters, VO2 max was calculated using the following formula: VO2 max = distance covered in meters -504.9/44.73.
Muscular endurance
The plank test was conducted to measure the strength and muscular endurance of female athletes. The athletes were instructed to lift their upper bodies off the ground using their elbows and arms as support and to lift their hips to form a straight line from the head to the toe, with their head facing the ground. The stopwatch was started as soon as the athlete took the correct position and the total time until they were able to hold their backs straight without lowering was noted.
Iron rich food consumption frequency
A food frequency questionnaire consisting of commonly consumed iron rich foods was used to analyze the pattern of consumption of iron rich foods by the female athletes [12]. The mean intakes of protein and iron were assessed using 24 h dietary recall for 3 d. Nutrient calculations were performed using DietCal software [Version: 13.0; Profound Tech Solutions programmed based on Indian Food Composition Tables 2017] [13].
Statistical analysis
Data were statistically analyzed using the Statistical Package for the Social Sciences (SPSS). Descriptive statistics are presented as the mean ± standard deviation and categorical data are given as frequency and percentage. Data were checked for normality using the Shapiro-Wilk and Kolmogorov-Smirnov tests. The Mann-Whitney U test was used for non-normally distributed variables, and independent t-tests were used for normally distributed data to determine the difference between athletes who were training in VB and BB. The relationship between endurance tests and hematological status was determined using Spearman’s correlation coefficient. Statistical significance was set at P < 0.05. The following cut-off values were used to determine the strength of the correlation between the two variables: negligible/no correlation (0.0, < 0.1), low correlation (0.1 < 0.3), medium correlation (0.3 < 0.5), high correlation (0.5 < 0.7), and very high correlation (0.7 < 1).
Frequency of consumption of cereals and pulses.
Frequency of consumption of nuts and seeds.
Frequency of consumption of non-vegetarian foods.
Frequency of consumption of green leafy vegetables, fruits and sugars.
Mean protein and iron intake of athletes.
RESULTS
Table 1 shows the descriptive statistics for the VB and BB athletes, and for all the athletes together. The VB athletes were significantly heavier and taller than the BB athletes (p < 0.001). They also had better endurance than BB athletes as reflected in their VO2 max levels (p < 0.001). Significant differences were not observed in hemoglobin levels; however, BB athletes had higher WBC (p < 0.018) and platelet levels (p < 0.002).
Descriptive statistics of female athletes of total group and according to their sport
Among all the athletes, 53.8% (n = 56) were anemic, with a higher percentage of BB athletes (31.7%) compared with that of VB athletes (22.1%) Table 2. Most athletes had normal WBC, RBC, and platelet counts.
Categorisation of hematological status of female athletes of total group and according to their sport
Approximately 58.7% of the athletes had been practicing their sport for 4-7 years and the majority of athletes participated at the collegiate and national levels (Table 3).
Training background of the athletes
Among all the athletes, those with higher than normal hemoglobin levels exhibited better endurance. Non-anemic athletes performed better than anemic athletes (Table 4).
Mean and standard deviation (SD) of endurance and haemoglobin (Hb) levels of female athletes
A moderate positive correlation was observed between hemoglobin level and cardiorespiratory endurance among VB athletes (Table 5). A significant correlation was exhibited between platelet level and muscular endurance for all athletes. Significant positive correlations were also observed among WBC count, hematocrit, MCV levels, and plank test results for BB athletes.
Correlation coefficient between endurance and hematological status
The frequency of consumption of iron-rich foods, including green leafy vegetables, organ meat, nuts, and seeds, was extremely low (Table 6). Jaggery is a good substitute for white sugar; however, it was not used by the majority of female athletes. The dietary iron intake of the athletes was found to be 12.11 mg and the mean dietary intake of the BB athletes (12.44 mg) was slightly higher than that of the VB athletes (11.79 mg).
DISCUSSION
This study aimed to correlate the hematological status of female athletes with their endurance levels. The study findings confirm that the cardiorespiratory and muscular endurance of non-anemic athletes was better than that of anemic female athletes and athletes with elevated levels of hemoglobin performed better. More than half of all the athletes were anemic and the dip in endurance of female athletes could be attributed to lower levels of hemoglobin.
The stature and weight of the VB athletes were higher than those of the BB athletes. A previous study of 163 elite female VB players reported body heights ranging from 161 to 194 cm [14], which is similar to the average height of VB athletes (166.45 ± 10 cm) in this study. The cardiorespiratory and muscular endurance of VB athletes was significantly higher when compared with that of BB athletes. An Indonesian study of female VB players also indicated that 40% of athletes had good levels of VO2 max [15].
A greater number of VB athletes had a normal BMI than BB athletes.
The average BMI of VB athletes in the current study (21.3 ± 3.02) was similar to the BMI levels of female VB players > 18 years of age in a study of 61 female VB athletes [16]. The near-ideal body composition of VB athletes could be attributed to their increased physical activity compared with that of BB athletes. The prevalence of anemia was 53.8% in all athletes, whereas it was 31.7% and 22.1% in BB and VB athletes, respectively. The Hb and RBC levels of these athletes were considerably low when compared with the Hb and RBC levels of elite Korean wrestlers, whereas their WBC levels were similar [17]. Despite the implementation of several governmental initiatives to reduce the burden of anemia in females, the prevalence remains high not only in non-athletic women but also in the athletic population [18]. An increased loss of iron is observed in female athletes owing to heavy training loads and altered hepcidin production in athletes with low energy availability and diminished carbo-hydrate intake [19,20].
Non-anemic female athletes performed better in the Cooper and plank tests, confirming the positive correlation between hemoglobin level and endurance [21] In endurance athletes, a close relationship may exist between changes in intravascular volume and exercise capacity [22]. A cross-sectional study involving 178 adolescents from the Physical Activity and Health Longitudinal Study (PAHLS) also demonstrated a moderately positive association between Hb and VO2 max in adolescent girls [23]. This study also showed a significant positive correlation between the WBC count and muscular endurance. Consistent with this, a plank test has been shown to improve immunocyte function [24]. A lower WBC count was observed in elite athletes training in aerobic sports than in team sport athletes, which is consistent with the current findings of a significant correlation between WBC count and muscular endurance [25].
The dietary intake of iron was much lower than the recommended dietary allowance for a normal adult woman, which is 29 mg/day [26]. The overall intake of dietary iron through the consumption of iron-rich foods must be increased to meet the recommended dietary allowances [20]. Nutritional interventions that can improve hematological status should be implemented by the government, especially for athletes. Providing nutrition education to female athletes can prove beneficial for athletes to include iron-rich foods along with a diet that is balanced in all other macro-and micronutrients, thereby enhancing performance [28].
This study demonstrated a positive correlation between hematological status and endurance levels in female athletes. The prevalence of anemia in female athletes is a cause for concern because of its impact on diminishing cardiorespiratory and muscular endurance. The consumption pattern of iron-rich foods highlights the need to encourage athletes to improve their iron intake through adequate intake of energy and protein, and regular consumption of iron-rich foods in combination with vitamin C-rich foods.
The strength of the current study is the determination of the complete blood count of female athletes (i.e., it was not limited to the estimation of hemoglobin alone), which has provided added insights into its relationship to endurance in athletes. Additionally, the use of venous blood instead of capillary blood to estimate hemoglobin eliminates errors in estimation.
One of the limitations of this study is that it only focused on the hematological status of female athletes; however, the assessment of their iron status through serum ferritin and transferrin levels strongly validate the results of the current study. Another major limitation is the lack of a non-athlete control group, which would have strengthened comparisons and clearly defined the effect of sports training on hematological status and endurance. The dietary intake of iron by athletes was self-reported and hence needs to be validated through future studies on female athletes using more accurate and validated food weight methods. Future studies with larger sample sizes for each type of sport and the inclusion of female athletes in other sport categories will further validate the findings of this study. An in-depth analysis of dietary patterns and sociodemographic factors will provide a better understanding of the causal relationship between hematological status and endurance in female athletes.