1. Introduction
The achievement of sports goals is conditioned not only by a wide range of motor and mental abilities [
1,
2,
3], but also by quality of diet, considering the increased demand for energy, fluids and some nutrients (carbohydrates, proteins, B vitamins, antioxidants and mineral salts). A varied diet, rich in products with high nutritional density and limiting those with low nutritional density, is one of the key factors contributing to health, improving exercise capacity and the effective post-exercise recovery of athletes [
4,
5].
One of the proposals for the rational nutrition of athletes is the model of the Swiss pyramid, which opens with water and other non-sweetened drinks, and ends with sweet and salty snacks. The intermediate levels of the pyramid are occupied by: vegetables and fruits, wholegrain cereal products, legumes, other protein products and vegetable fats, recommended for consumption in various amounts, and at a certain frequency. This model emphasizes the special importance of water for the regulation of hydration and electrolyte management, as well as vegetables and fruits for maintaining appropriate antioxidant status and acid-base balance in conditions of vigorous physical exercise [
6].
The health quality of a diet, related to the implementation of quantitative and qualitative dietary recommendations, can be assessed using various indices, including the healthy diet index (HEI), the Australian diet quality index (Aussie-DQI) [
7,
8,
9] and the pro-healthy diet (pHDI-10) and non-healthy diet (nHDI-14) indices functioning in the Polish literature. The pro-healthy diet index concerns the frequency of consuming products with potentially beneficial effects on health, while the non-healthy diet index concerns the consumption of products potentially detrimental to health [
10].
Nutritional behaviour is determined by numerous factors, including environmental and individual conditions [
11,
12,
13]. An important area of determinants regarding food choices are psychological factors, including personality traits. Personality is treated as an internal regulatory system that allows for adaptation to selected situations and the environment as well as internal integration of thoughts, feelings and behaviours [
14]. One of the models regarding the approach to personality and its description is the five-factor model of personality by Costa and McCrae, which, in the last few decades, has become one of the dominant paradigms in the psychology of traits [
15]. The so-called big five model by Costa and McCrae [
16] consists of five main dimensions of personality, including
Neuroticism,
Extraversion,
Openness to Experience,
Agreeableness and
Conscientiousness (and constituent features of these dimensions). The dimensions of the big five offer the possibility to comprehensively and factually describe, and interpret personality in terms of five major domains: general activity and contact, emotional balance, the way of relating to people, the way of relating to tasks, and general reference to the world and new experiences [
14,
16].
Personality is also important for the quality of food choices, which was demonstrated, among others, in young adults from New Zealand, university students from Ghana and physical education students from Poland and Spain [
17,
18,
19]. Among physical education students, the intensity level of a pro-healthy diet has been described along with an increase in the levels of extraversion and conscientiousness [
19]. In research on the subject, it has been shown that people practicing sports are characterised by a lower level of
Neuroticism, which is conducive to more favourable eating behaviours [
20]. In other studies, it has been indicated that
Conscientiousness is associated with reduced exposure to psychoactive substances (alcohol and tobacco) and increased consumption of vegetables and fruits [
21]. In research on the subject, it has also been demonstrated that high
Extraversion and
Conscientiousness were conducive to undertaking physical activity and applying a healthier lifestyle [
22,
23,
24]. It was also confirmed that
Conscientiousness and
Openness to Experience are predictors of occupational burnout and lower quality of life among athletes [
25]. A research hypothesis has been formulated in reference to the results of the above-mentioned research. The mostly positive predictive significance of extraversion and conscientiousness have been suggested, as well as the negative significance of neuroticism for health-related behaviours, including nutritional ones among various population groups [
17,
18,
19,
20,
21]. Another premise of the adopted research hypothesis regarded the characteristics of individual personality dimensions, including neuroticism (associated with emotional lability), extraversion (associated with positive emotion) and conscientiousness (associated with the ability to control stimuli and focus on achievement striving) [
14,
15,
16].
Due to the significance of diet quality for the health and exercise capacity of athletes, complexity regarding the determinants of nutritional behaviour, the lack of exploitation on the subject correlations between personality and diet as well as the ambiguity of the study results obtained so far, research was undertaken on the personality determinants regarding athletes’ diets. The aim of the study was to analyse the personality determinants of diet health quality among an elite group of Polish team athletes. The relationships between the personality traits of the big five model and the indices of diet health quality (pHDI-10 and nHDI-14) were assessed. The following research questions were posed: (1) What are the indices of diet health quality among athletes? (2) What are the personality traits of athletes? (3) What are the correlations between the personality traits and the diet quality among athletes? A research hypothesis was adopted stating that personality traits are related to the diet health quality of athletes, with higher indices of a pro-healthy diet fostered by Conscientiousness and Extraversion, and less favourably—by Neuroticism.
4. Discussion
The research discussed in this paper allowed us to demonstrate a low level of diet health quality, a low level of neuroticism and significant correlations between certain personality dimensions and health quality indices of the diet among Polish team athletes (males).
When discussing the results in terms of diet health quality, referring to the applied methodology [
10], a low level of the pro-healthy (19.16 points) and non-healthy diets (15.69 points) was shown. This should be interpreted as a limited, both positive and negative impact of diet on the health of the athletes under study. The low level of the pro-healthy diet index (pHDI-10) among athletes was related to the low frequency of consuming recommended products, including fruits and vegetables, wholemeal bread and other low-milled cereal products and legumes, as well as milk, dairy products and sea fish. These are products with high nutritional density, containing, among others, antioxidant substances, dietary fibre and omega-3 polyunsaturated acids, as well as probiotics, ingredients with significant pro-health values, including active ones, e.g., in the prevention of cardiovascular, metabolic and neoplastic diseases [
28,
29,
30,
31]. Due to the increased formation of free radicals under conditions of vigorous exercise, a diet rich in vegetables, fruits, legumes and specific products containing antioxidant ingredients (including polyphenols and vitamins C, E and carotenoids) is important for restoring pro-oxidative-antioxidant balance and reducing oxidative stress indices in athletes [
31,
32,
33,
34].
The demonstrated low level of the pro-healthy diet among elite Polish team athletes corresponds to nutritional, quantitative and qualitative irregularities shown in various groups of athletes, including those training team disciplines, both in Poland [
35,
36] and in other countries [
37,
38,
39,
40,
41,
42,
43]. Varying levels of diet quality indices among athletes have also been found in various studies. High health quality of the diet (based on the athlete diet index, ADI), related to the sufficient consumption of recommended products, including vegetables, cereals and dairy, was described among Australian athletes of individual and team sports [
44]. On the other hand, in Brazilian studies (using the healthy eating index, HEI), a low health quality of the diet was confirmed in approximately 73% of the group of athletes training volleyball, indicating a low supply of vitamins A and E [
45]. An average level of diet quality (according to the HEI index) was described among athletes practicing team [
46] and individual sports [
47], and among academic athletes [
48]. In Poland, the low health quality of diet (based on HDI indices) has also been described among young football players [
49] and in other groups of individuals undertaking increased levels of physical activity, including physical education students [
19,
50] and aging masters athletes [
51].
In our research, it was further shown that in terms of personality profile, the elite group of Polish team athletes was characterised by the highest scores regarding dimensions of conscientiousness, agreeableness, extraversion and openness, and the lowest in terms of neuroticism. Comparing raw scores to sten norms (for men aged 17–29 and 30–79) [
27], it can be indicated that the studied athletes were characterised by a high level of conscientiousness, agreeableness, extraversion and openness (7–8 sten, depending on age) and a low level of neuroticism (3–4 sten, depending on age).
In our study, it was also shown that the elite group of Polish team athletes was characterised by a high level of the Conscientiousness, Agreeableness and Extraversion dimensions, a lower level of Openness to Experience, while the lowest level was Neuroticism in terms of the personality profile. It should also be pointed out that it is not the intention of the authors to conduct an advanced analysis of the personality profile of athletes, but only to comprise a general characteristic of the personality traits’ configuration to such an extent that it constitutes a background for the assessment of psychological determinants regarding diet health quality.
In further studies on the personality of athletes, different trends were shown. Athletes practicing team sports (football, handball and water polo) obtained the highest scores in terms of
Openness to Experience,
Agreeableness and
Extraversion, but lower values in terms of
Conscientiousness, and the lowest with regard to
Neuroticism [
52]. Similarly, in the next group of athletes performing team sports, the highest levels of
Openness to Experience and the lowest of
Neuroticism were demonstrated [
53]. Therefore, it may be concluded that, despite the different configuration of features, the trend occurring in the majority of studies conducted among professional athletes is the lowest intensity of the
Neuroticism dimension among the features included in the Costa and McCrae five-factor model. The low level of
Neuroticism among athletes was also confirmed among Polish athletes by other authors [
20], especially with regard to championship athletes [
54,
55].
Furthermore, statistically significant relationships were exhibited in our study between the personality traits of the big five model (and their subscales) and the assessed indices of diet health quality (however, mostly weak). In terms of the diet health quality indicators, predictive significance of Neuroticism, Extraversion and Agreeableness was found. The performed multiple regression analysis confirmed a very high share of the analysed personality traits in explaining the variance of diet quality indicators (above 88%). High Neuroticism (and its subscales: high anxiety, hostility/anger, depression and self-consciousness) was associated with a decrease in the health quality of the diet (i.e., a decrease in the pHDI-10 pro-healthy diet index) and a decrease in the frequency of consuming products with high nutritional density (e.g., vegetables and sea fish). High Extraversion (and its subscale: high activity level/lively temperament) was associated with an increase in the overall pro-healthy diet index (pHDI-10) and with a greater frequency of consuming products having high nutritional value (including vegetables and milk). High Agreeableness (and its subscales: high fantasy/imagination and high trust in others) was associated with a lower non-healthy diet index (nHDI-14), while high modesty was connected with a lower level of the pro-healthy diet index. On the other hand, significant correlations were found between some personality traits and the frequency of consuming individual products with potentially beneficial and potentially unfavourable effects on health, while unambiguous positive trends were shown only in terms of Conscientiousness (with its intensification, the consumption of vegetables increased). Other relationships were less clear.
The obtained results confirm the difficulties in unambiguous assessment of the relationship between personality traits and diet, including its health quality. The greatest number of unambiguous correlations at the level of overall nutritional indices was noted for Neuroticism (indicating its negative predictive importance for the health quality of diet) and Extraversion (indicating its positive predictive importance for the health quality of the diet). One can also indicate the dimension of Openness to Experience (with an indication of the positive meaning of one of the fantasy/imagination subscales).
Similar correlations between personality traits and food choices among various population groups were also described at others research centres, including in our previous studies. In analogous trials carried out among academic youth performing increased levels physical activity (Polish and Spanish physical education students), partially similar regularities were shown. It was noted among PE students that with the intensification of
Extraversion, the level of both diet health quality indices (pHDI-10 and nHDI-14) increased (in Polish team athletes, only pHDI-10). At the same time, with increasing
Openness to Experience and
Agreeableness, the value of the non-healthy diet index (nHDI-14) decreased (in Polish team athletes, this relationship occurred only for
Agreeableness). Along with the increase in the level of
Conscientiousness, the pro-health quality of the diet increased (pHDI-10 index), which was not noted among the athletes under study [
19]. At the level of personality relationships with the consumption of products recommended and not recommended in the diet, high correlations were noted for
Extraversion and
Conscientiousness with the consumption of fruit and vegetables, high
Extraversion with the consumption of sweets and confectionery, and high
Neuroticism with a low consumption of sea fish [
19]. The indicated tendencies are consistent with the regularities described among the evaluated athletes performing team sports. The significance of personality traits for the quality of food choices was also described among academic youth from New Zealand (here, a positive correlation was found between
Extraversion and fruit consumption) [
17] and among students from Ghana (here, inter alia, between
Extraversion and interest in new food products, associations of
Agreeableness with irregular consumption of meals and
Conscientiousness with a variety of diets and limiting sugar consumption) [
18]. In contrast to our study, in research carried out among the Indonesian population, it has been shown that
Conscientiousness is the only personality dimension that is clearly positively related to rational food choices [
56]. Nonetheless, conclusions from other studies correspond to the results obtained in our research under discussion. Other studies conducted in Indonesia aimed at assessing the relationship between personality traits and body mass index (BMI), and demonstrated that individuals with excess body mass were less extroverted (i.e., more introverted) than people with normal body mass, which may indirectly indicate more rational food choices (and greater physical activity) of more extroverted people [
57]. Research on the relationships of personality traits, eating behaviours and the BMI factor was also undertaken in the Australian population, which allowed the confirmation (among other findings) that nutrition, also applied in the Australian population, was considered a healthy pattern based on plant foods (vegetables, fruits, legumes) and fish was positively associated with
Openness,
Conscientiousness and
emotional stability, and that BMI was negatively correlated with
Conscientiousness and
emotional stability, and positively with
Agreeableness [
58]. The cited Australian studies correspond with the results obtained for Polish team athletes with regard to correlations between low neuroticism levels and higher diet quality.
It may be summarised that various studies on personality determinants of nutritional behaviours in different population groups sometimes yield varied and ambiguous results. Nonetheless, the obtained results can be of practical usage for strategies aimed at changing (nutritional) behaviour due to the potential possibility of an interaction consistent with personality traits, assuming that personality is a rather permanent configuration of traits. However, further research conducted with interdisciplinary teams is needed to explain the mechanisms of the observed dependencies, which has also been pointed out by other authors [
56].
Nutritional irregularities demonstrated among athletes justify the need to monitor diet and nutritional education, taking individualisation of effects promoting a healthy diet into account. Assessing the predictive significance of personality traits included in the big five model, in accordance with the sports nutrition model, should contribute to the effective rationalisation of diet through the individualisation of potential educational and dietary interactions due to the possibility of developing a strategy cohesive with personality profile.
The limitations of the work are primarily related to the lack of including demographic and sports variables (age, professional experience, discipline) in the analysed variables, taking one selected nutritional area (diet quality) into account and the self-report nature of the research tools used. It should also be highlighted that the achieved results only relate to men. The indicated and other limitations may determine the directions of further research, the aim and subject of which should be a comprehensive assessment of personality determinants regarding various areas of sports nutrition, taking age, gender, sports level and type of discipline into account. Further research in this area may include personality determinants of nutritional behaviours, including post-exercise nutrition and the use of dietary supplements (including ergogenic aids) by athletes. An important field in future research could also be the assessment of potential relationships between personality profile and quantitative aspects of sports nutrition (i.e., with the supply of energy and nutrients).