This is the first study of its kind to assess the association of nutrition knowledge, practice, and nutrient intake and supplementation use with athletic performance among Taekwondo players in Nepal. Good nutritional knowledge, practice, and adequate nutrient intake are considered a crucial components contributing to athletic performance [30].
In this study, based on the correct response of the nutrition knowledge and practice score, the study participants demonstrated a relatively low level of nutrition knowledge and practice compared to previous findings where less than half had poor nutritional knowledge [17,31]. However, our result is in line with the other studies report where overall nutrition knowledge scores were low [10,32]. Optimum nutrition knowledge is an essential factor for promoting athletic success to the sportsperson [9,10]. Inadequate nutrition knowledge can have a serious impact on the nutritional status and performance of athletes [11]. The study conducted by Walsh et al (2011) showed that poor nutritional knowledge and attitudes (dietary behaviour) had contribution to poor dietary behaviors [14]. This study revealed that those athletes who had poor nutrition knowledge were found to have poor nutrition practice scores. These findings were in line with previous findings where the correlation between nutrition knowledge and practice score of athletes were found statistically significant [17,33]. Lack of knowledge about nutrition in sport is considered as one of the potential barriers to optimal nutrition practices among athletes [16].
The prevalence of supplement use in the current study was found to be lower than that reported in other studies [9,18]. Overall, 7.2% of Taekwondo players in our study used some form of supplements. Likewise, Muwonge et al (2017) also reported the supplement-use prevalence to be 13.4% [34], which is also low compared to previous study findings [9,18,35]. The professional TKD players may readily use nutritional supplements mainly to maintain their health and improve athletic performance. The possible explanation for these findings could be that the assessment tools for supplements use adopted by the current study may have underestimated the true prevalence.
In this study, a total energy intake, carbohydrate, protein, fat, calcium, and iron were significantly lower than the corresponding RDA. Every athlete including TKD players needs adequate calorie from the diet in terms of optimum quality and quantity before, during, and after exercise for improved athletic performance [6]. Adequate nutrient intake and good nutrition knowledge have been recognized as key factors in improving the athletic performance, particularly in improving quality of training and recovery from injury. The median carbohydrate intake of the participants was 430.5gm in this study. This is equivalent to 87.1% of RDA's recommended value for athletes within this population. This result is consistent with results from Wierniuk et al (2013) and Ali A et al (2015) [11,36]. Carbohydrate is essential not only as a source of energy but it also protects the protein from being exploited as an energy source [37,38]. Inadequate intake of carbohydrates increases the risk of injury and exaggerates deterioration of athletic performance [32,38]. Thus, carbohydrate intake before, during, and after exercise should be scaled up according to the characteristics of the event. Even small amounts of carbohydrate solution like mouth-rinsing without swallowing, increases athletic performance through the pathway that involves central nervous system in its absorption [37].
The median protein intake of the participants was 79.5gm. The protein intake was found to be inadequate in this study (only met 58.8% of corresponding RDA for athletes within this population). Inadequate protein consumption can have serious health problems in athletes such as inability to maintain proper body function and decline in sports performance [21]. A previous study showed that a protein intake of 1.4-2.0 g/kg body weight could improve body adaptability for intensive physical activities [39]. Adequate protein intake is critical in the overall exercise training program, required for a proper and speedy recovery from injury including to bolster immune function, growth and maintenance of lean body mass [39].
The median fat intake was found to be low (71.2gm) in this study, which is only equivalent to 57.4% of RDA recommended value for athletes within this population. This finding is inconsistent with other findings, where the fat intake was found to have higher than RDA [32,36]. Fat is an essential component of a balanced diet, providing energy, optimum elements of cell membranes, and facilitation of the absorption of fat-soluble vitamins [40].
The median energy intake in these participants was 2367.8 kcal/day, which is lower than the corresponding RDA, and is slightly lower than reported in the previous study in Indian Taekwondo athletes (the mean energy intake was 3129 ± 518.9) [4]. Nutrition and Hydration Guidelines states has categorized weight division game such as TKD under Group-IV sport event which demands a minimum 3600 Kcal of daily calorie, that means 65%, 15%, and 20% should be yield from carbohydrate, protein, and fat respectively [41].
The median intake of micronutrients: calcium (416 mg) and iron (7 mg) were below the RDA, which can meet only 47% and 32% of RDA value for athletes within this population. These findings are in line with the results from the other studies [4,32], where their results were also below the RDA. Adequate intake of iron, which is necessary to carry oxygen, and maintain energy production, is critical for female athletes during the high-intensity exercise, owing to their iron loss during regular menstrual cycle [42]. In addition, a sufficient amount of calcium-rich diet contributes to bolster bone mineral density and prevent injury risk [32].
Anthropometric characteristics such as height, weight, and BMI were positively correlated with athletic performance. These results are consistent with the previous studies where they reported that handgrip strength had a strong correlation with various anthropometric characteristics [17,24]. In this study, results indicated a significant relationship between NK score and athletic performance. Various previous studies reported that nutrition knowledge was positively correlated with athletic performance [14,17,33]. Higher nutrition knowledge of the athletes, better their attitude and practice towards a sport-enhancing diet, resulting better performance [33]. Likewise, total energy and fat intake were significantly positively correlated with handgrip strength of athletes. The previous study also reported that energy intake was positively associated with handgrip strength [17]. The most important component to optimize athletic performance through diet is to ensure the athlete is consuming enough calories to maintain positive energy balance [7,19]. However, it might be challenging to meet the energy needs of athletes with a high volume of intense training. Insufficient energy intake can result in weight loss, especially lean muscle mass, injury, illness, increased prevalence of overtraining syndrome, and ultimately decreased exercise performance [43]. Moreover, in linear regression analysis, the DHGS were positively associated with training hours per day, BMI, NK score, and energy intake. These results are consistent with Folasire OF et al (2015) findings. For better athletic performance by athletes, an adequate energy balance is needed, where energy balance occurs only when energy intake such as foods, fluids, and supplement products are equivalent to energy expenditure [21]. Energy expenditure for various exercise is dependent on the duration, frequency, intensity of the exercise, sex, age, body size of the athletes. The more energy used in the exercise, the greater calories required to achieve energy balance [40].
Our study had a few limitations. The sample size used in this study was confined to Taekwondo players, thus we cannot generalize the findings to all types of sports. There are slight differences in nutritional requirements depending on the type of sports. We used a 24-hour dietary recall method which can underestimate true nutrient intake. Also, single 24-hr recall cannot identify within and between-person variations. Although other minerals and vitamins play a key role in human health and nutritional status, we included only calcium and iron as micronutrient intake. Since the information was collected through face-to-face semi-structured questionnaires, there may have been social desirability bias. Due to the limited resources, we could not measure the body composition using a portable body composition device and also could not assess the other anthropometric measurements such as waist, neck, hip circumference. Despite the mentioned limitations, our study has some strengths. Our study included an analysis of the correlation between nutritional knowledge, practice, and nutrient intake with athletic performance. This data provide insight into the potential factors influencing athletics performance which helps in forming the basis of targeted nutrition education programs. The majority of the national Taekwondo clubs were located in Kathmandu Metropolitan City, however, the study sample included players from all levels from Nepal. The results of this study can be a reference to reform the nutritional policy for all types of athletes. This study has also set the premise to build further evidence to explore the determining factors for the nutritional knowledge and practices among Nepalese athletes.