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Article

Trends in Protein Supplement Use Among Non-Professional Athletes: Insights from a Survey in Greece

by
Panagiota Athanasopoulou
1,2,†,
Georgia-Eirini Deligiannidou
1,3,†,
Paraskevi Basdeki
4,
Elena Deligianni
1,
Pinelopi Kryοna
3,
Georgios Kaltsos
3,
Diamanto Lazari
4,
Athanasios Papadopoulos
3,
Konstantinos Papadimitriou
3,* and
Christos Kontogiorgis
1,*
1
Laboratory of Hygiene and Environmental Protection, School of Medicine, Democritus University of Thrace, Dragana, 68100 Alexandroupolis, Greece
2
Department of Nutritional Science and Dietetics, School of Health Sciences, University of Peloponnese, Antikalamos, 24150 Kalamata, Greece
3
Department of Nutritional Sciences and Dietetics, International Hellenic University, Sindos, 57400 Thessaloniki, Greece
4
Department of Pharmacognosy-Pharmacology, School of Pharmacy, Faculty of Health Sciences, Aristotle University of Thessaloniki, 54124 Thessaloniki, Greece
*
Authors to whom correspondence should be addressed.
†
These authors contributed equally to this work.
Physiologia 2025, 5(2), 18; https://doi.org/10.3390/physiologia5020018
Submission received: 6 May 2025 / Revised: 6 June 2025 / Accepted: 9 June 2025 / Published: 12 June 2025
(This article belongs to the Special Issue Exercise Physiology and Biochemistry: 2nd Edition)
Browse Figures
Review Reports Versions Notes

Abstract

:
Objective: Protein supplements (PSs) are widely consumed by professional and non-professional athletes, yet research on non-athletic PS users’ perceptions, motivations, and health risk awareness is limited. This study aimed to investigate non-professional athletes’ PS patterns of use, motivations, and safety. Methods: A cross-sectional study was conducted using a constructed questionnaire reporting on PS usage trends, exercise habits, and demographic factors. Adult respondents were recruited from gyms, athletic organizations, amusement parks, and playing fields. Results: We received 1100 responses, and 327 were PS users. From the total of PS users, there was a prevalence of PS use in males [(203 (62%)]; adults in the age group of 25–34 [136 (42%)], p < 0.001; and participants with a normal BMI (189, 58%), p < 0.001. Following high-intensity fitness exercise sessions and engagement with more than two types of physical activity were associated with more than doubled odds of PS consumption (p < 0.001). The main reasons for PS intake were for muscle mass increase (35%) and recovery (18%), and protein powder was the most popular PS (279; 64%). The main channels of information for PS use were Web/social media (50, 40%) and coaches (54, 43.2%), while one out of two [35 (49%); p = 0.008] of those engaged in more than two types of physical exercise declared that PSs are good for health. Conclusion: The findings highlight demographic, behavioral, and informational factors shaping PS consumption in non-professional athletes. Despite the perceived benefits, reliance on non-expert sources and unregulated products raises concerns about consumer awareness and safety, while educational initiatives to promote evidence-based supplementation practices are deemed crucial.

1. Introduction

Protein supplements (PSs) constitute the most popular dietary supplements (DSs) among athletes and physical activity practitioners [1]. PSs may be used to replace a meal or supplement the diet for a variety of purposes, such as controlling weight, increasing body muscle mass, improving athletic performance, and post-exercise recovery [2,3]. Numerous studies have investigated the physiological impact of protein supplements on muscle growth, recovery, strength, and overall health [4,5,6], as well as the effects of supplementation on muscle soreness and function, confirming the benefits for athletes and casual exercisers alike [3,7]. In this setting, previous research by Poulios et al. concluded that while some studies suggest PSs may relieve muscle soreness, reduce muscle damage markers, and moderate inflammation, the evidence is too limited and inconsistent to support clear guidelines for their use in team sport recovery [8]. Additionally, a recent article by Karpouzi et al. reported that increasing protein intake from 1.0 to 1.6 g/kg/day did not enhance performance outcomes, suggesting that short-term high-intensity functional training (HIFT) improvements in exercise capacity, upper-body strength, and core endurance were not influenced by PS [9]. Interestingly, in a research report published the same year by this research group, it was demonstrated that although Pilates improved core endurance, flexibility, and body composition, the consumption of PS (0.6 g/kg) had no additional effect [10]. Key insights regarding the patterns of PS consumption are reported by Tsitsimpikou et al. (2011) [11], documenting that 41% of the recreational athletes in Athens consumed supplements, primarily proteins and amino acids, with limited professional guidance, while research among Mediterranean athletes indicated that supplementation often exceeded dietary needs [11,12].
On the other hand, high prevalence rates of supplement use have been observed among elite athletes in Spain (64%) and recreational triathletes in Brazil (90.2%), often without adequate professional consultation or awareness of supplement safety [13,14]. Notably, the prevalence of PS usage may vary depending on the population group being studied, geographic location, and specific demographic characteristics. However, the observed increase in PS use in recent years may also be driven by a variety of factors such as fitness trends, increased interest in body image, healthy lifestyle, and wellbeing, as well as marketing advertisements by supplement companies. Additionally, the choice of a PS depends on individual preferences, tolerance, dietary restrictions, and the specific fitness goals of the practitioner. As such, PSs widely available in the market include different protein types such as whey, casein, soy, plant-based, and egg white protein, formulated with additional ingredients, such as carbohydrates, electrolytes, and vitamins, to support recovery after intense physical activity, while different types can affect amino acid bioavailability [15].
While protein supplementation offers benefits, excessive or inappropriate use may carry health risks, as current studies highlight the importance of informed and balanced supplementation practices to prevent unintended consequences [16,17,18]. Excessive protein intake is associated with dehydration, kidney damage, nutrient imbalance, and digestive disturbances, including discomfort, bloating, gas, and constipation [18,19]. Despite the potential serious health risks, many physically active practitioners proceed in use without a full understanding or evaluation of the benefits and risks associated with PS use, and also without consultation or support from healthcare professionals (HCPs) [16]. A key concern regarding PSs stems from the often-limited information on the labels regarding their elemental composition, noting that overexposure, chronic use, or excessive daily intake of PSs contaminated by cobalt, zinc, and manganese are associated with genetic diseases [20]. Given that some essential elements, such as iron, manganese, or zinc, may be toxic at high concentrations and become harmful to consumers, recent studies explore the global regulatory landscape, whereas others also focus on the prevalence of supplementation in specific communities [21,22,23,24]. These studies collectively capture the socio-economic and regulatory factors shaping supplement usage worldwide.
The Recommended Dietary Allowance (RDA) of protein needs for healthy adults with minimal physical activity is 0.8 g/kg/day, while with moderate and intense physical activity it ranges between 1.0 and 1.8 g/kg/day [25]. Nitrogen balance studies recommend that the daily requirements for protein rely on the number of amino acids irreversibly lost due to the extra protein required to support muscle protein accretion through elevated protein synthesis or due to the increased catabolic loss of amino acids associated with strength-training activities [26,27,28]. However, current studies suggest a high prevalence of PS use due to misunderstanding or lack of counseling with a nutrition or sports expert, especially for timing, frequency, and doses of use, which are also associated with factors such as age, gender, individual’s lifestyle, type, and degree of physical activity [29,30].
In this setting, previous studies have evaluated the level of understanding of how and why physically active individuals, including non-professional athletes, gym users, and fitness enthusiasts, use PSs as well as their beliefs about the benefits or risks of PSs, and the factors that influence their decisions on PS intake [23,24,31,32]. The majority of previous research has concentrated on elite or professional athletes, with limited evidence available on the beliefs, attitudes, and practices of non-professional athletes and fitness enthusiasts regarding PS use in Greece. Moreover, there is insufficient evidence regarding the complex interplay of factors influencing PS use, including individual motivations, sources of information, and awareness of regulatory frameworks and potential health risks among this diverse and recreationally active population. Considering the increasing popularity of fitness culture, the evolving supplement market, and changing consumer behaviors, it is essential to investigate the current patterns of PS use and perceptions among non-professional athletes.
The current cross-sectional study aimed to address these gaps by investigating the following: (a) the beliefs and attitudes of physically active individuals regarding their PS use patterns and motivations; (b) protein supplement users’ sources of information and awareness of regulatory frameworks for supplement safety; (c) users’ perceptions of health risks associated with PS intake, including experiences of adverse side effects.

2. Results

2.1. Demographic Characteristics of Participants

The questionnaire was completed by 1100 respondents (Table 1), the majority of whom were female, with an average age of 29 years. Among them, 30% reported PS use, with males significantly more likely to be consumers (p < 0.001). Age was also a determining factor, with the highest prevalence observed among young adults aged 25–34 years (p < 0.001). Most respondents had a normal BMI, and this group reported significantly greater protein intake compared to others (p < 0.001). While educational background did not show a statistically significant impact on PS consumption (p = 0.175), smoking status did, with non-smokers representing a significantly larger proportion of users (p = 0.02). Professional exposure to fitness-related exercise influenced PS use, but intake was significantly higher among those not employed in sports-related fields (p < 0.001). Also, perceptions regarding PS safety regulations were notably influenced by fitness status and occupation, with fitness enthusiasts and those working in sports being more likely to believe PSs undergo regulatory processes similar to medications (p = 0.02 and p = 0.01, respectively). In summary, demographic data indicate that the prevalence of PS use was 30%, with higher intake among males (62%) compared to females (32%; p < 0.001). Younger participants (18–34 years), those with normal BMI (18.5–24.9 kg/m2), and non-smokers (p = 0.02) reported greater use. PS intake was higher among non-sports professionals (p < 0.001).
A logistic regression analysis identified several significant predictors of PS use. Gender was a strong determinant, with males exhibiting higher odds of consumption (OR = 0.313, 95% CI: 0.234–0.419, and p < 0.001). Age also played a role, with individuals aged 25–34 being more likely users (OR = 1.206, 95% CI: 1.026–1.417, and p = 0.02). The level of exercise was a significant factor, with increased physical activity associated with more than doubled odds of PS use (OR = 2.122, 95% CI: 1.653–2.724, and p < 0.001). Fitness engagement emerged as a strong predictor, with high-intensity fitness activities linked to an increased likelihood of PS consumption (OR = 3.496, 95% CI: 2.528–4.834, and p < 0.001). Additionally, individuals participating in more than two types of physical activity had significantly higher odds of PS use (OR = 1.906, 95% CI: 1.280–2.836, and p = 0.001). A graphical representation of these results is provided in Figure 1.

2.2. Responses for PS Use by Non-Professional Athletes

Further analysis of the participants’ responses regarding PS use (Figure 2) revealed that the primary reasons were muscle mass increase (35%) and muscle recovery (18%). Other motivations included athletic performance enhancement (15%), weight loss (13%), and energy boost (9%). Statistical analysis identified significant associations between specific reasons for PS use and individual characteristics, particularly related to age groups, gender, and BMI class (Table 2). Additionally, among those using PSs for muscle mass gain, the majority engaged in moderate-level physical exercise (60%; p = 0.01). Education level also played a role, with muscle recovery users primarily being secondary education graduates (43%), followed by undergraduate (33%) and postgraduate (24%) degree holders (p = 0.004). Also, the individuals participating in mixed exercise (29%) and fitness training (25%) were more likely to use PSs for muscle recovery compared to those involved in aerobic or anaerobic exercise (p < 0.001). Finally, among the users consuming PSs for muscle recovery, moderate exercise was the most common regimen (68%; p < 0.001).
Weak to moderate associations (Table 2) were recorded regarding the reason for using PSs and key characteristics such as gender (male), age groups (those of 35–44 years), and BMI. Slightly higher among these associations were those related to muscle recovery, performance increase, and energy increase.
It is worth noting that the users who were overweight (51%) had a significantly greater percentage of PS use, reporting that it increased their athletic performance; p = 0.01. Those who mainly followed mixed-type exercise 35 (35%) and fitness programs 31 (31%) tended to use PSs to increase their athletic performance, p < 0.001, compared to individuals following other types of exercise (aerobic and low exercise). From those who used PSs to increase their athletic performance, the majority followed moderate-level exercise, 63 (62%); p = 0.01. Additionally, amongst the participants who reported PS use mainly for weight loss, most of them followed mixed exercise type 30 (33%) and fitness 23 (25%); p < 0.001. Regarding the regime of consumption of PS (Figure 3), the outcomes of our study demonstrated that more than half of the PS users (55%) preferred to consume protein supplements following their workout routine, while 20% tended to use PSs before their workout, and 19% of the respondents consumed PSs anytime during the day. A limited number of respondents referred to protein consumption during a workout (4%) or when they were hungry (3%).
On the evaluations regarding the protein supplements the participants would commonly consume, the study did not differentiate strictly between high-protein foods (such as protein bars or shakes) and protein supplements in the form of powder or tablets. However, the responders were asked to only reflect on what they consumed beyond their daily intake of protein stemming from their diet. In this setting, the participants were given the following options: protein bars, protein shakes, protein powder, and protein tablets, and were asked to respond to their consumption preferences, being able to choose more than one type of PS (Figure 4).
Among the PS users, protein powder was the most popular choice for both sexes, with 279 responses (64%), followed by protein chocolate bars with 95 positive responses (22%), and protein shakes with 61 (14%) positive responses (Figure 4A). It is noteworthy that the majority of the PS users who showed a preference for protein powder were also fitness enthusiasts 123 (44%), p < 0.001, and followed moderate- 151 (54%) and low 113 (40%)-intensity exercise programs; p = 0.02.
An essential outcome of this survey is that among the 327 respondents who reported using protein supplements, various side effects were identified (Figure 5). The most commonly self-reported issues included sleeping disturbances (16%), aggression (14%), and nausea (12%). Additional side effects experienced by the users included changes in hematology tests (12%), high blood pressure (12%), aches (11%), dizziness (9%), and allergic reactions (8%). The side effects reported by the respondents are presented in Figure 5. Noted in blue color in the figure are the positive responses disclosed by the participants regarding consulting a medical doctor after having these side effects. Notably, the proportion of respondents consulting a medical doctor was higher for males when the side effect was high blood pressure or changes in blood test, and for females when the effects were related to sleep disturbances and dizziness.
Given the outcomes of this analysis, we have further aimed to investigate the potential relations with the participants’ perceptions of safety control of protein supplement use as well as the key resources and channels of information (Table 3).
According to self-reported data from the PS users, the type of exercise significantly influenced their choice of information sources regarding PSs. Among the most frequently consulted channels were social media, particularly among fitness enthusiasts (50 respondents, 40%) and individuals engaged in mixed exercise (45 respondents, 36%). Another prominent source of PS-related information was sports coaches, with fitness enthusiasts relying on them most frequently (54 respondents, 43.2%), followed by those participating in mixed exercise (29 respondents, 23.2%). Notably, only a small proportion of PS users expressed trust in healthcare professionals (HCPs) as a source of PS-related information, with 18 respondents (39.1%) from the mixed exercise group and 13 respondents (28.3%) from the fitness enthusiast group indicating reliance on HCPs (p = 0.005).
Regarding preferences for PS procurement, the majority of the respondents who were either uncertain about using a pharmacy as their primary PS source (58 respondents, 60.4%) or actively avoided pharmacies due to cost-related concerns (100 respondents, 69.9%) were male PS users (p = 0.01). The perceptions of PS safety regulations by authorities were significantly influenced by fitness status, exercise type, and occupation. Among the fitness enthusiasts, 78 respondents (59%; p = 0.02) supported the notion that PSs undergo regulatory processes similar to those applied to pharmaceuticals. Similarly, the individuals working in sports-related occupations expressed confidence in such regulations (62 respondents, 62%; p = 0.01; Table 3). Furthermore, among the respondents engaging in more than two types of physical exercise, approximately half (35 respondents, 49%) believed that PSs contribute positively to health (p = 0.008).

3. Discussion

This study provides valuable insights into the perceptions, attitudes, and health risk awareness of non-athletic PS users. Our study identified gender, age, and BMI as significant predictors of PS use, with higher consumption reported among males, younger adults (18–34 years), and individuals with a normal BMI (18.5–24.9 kg/m2). These findings are consistent with previous research, which highlights that PS users are predominantly males and young adults with normal weight [23,24]. Conversely, a study in the Jazan region observed that 90.8% of female non-athlete gym attendees consumed PS compared to 77.6% of males [33]. This suggests that cultural and regional factors may influence supplement patterns. In our study, the educational level of the participants was not a significant predictor of PS use; however, the participants with undergraduate education reported higher intake. Other studies suggest that socio-economic status may play a role, with higher education and occupational positions linked to increased supplement use [34,35].
Our data indicates that smoking status influenced PS use, with non-smokers reporting higher usage. Interestingly, the participants not employed in sports-related fields showed higher PS consumption. These findings align with research suggesting that non-smokers are generally more inclined to use PSs, likely due to broader health-conscious behaviors [23,34]. Moreover, supplement use among non-sports professionals may be driven by personal health and fitness goals, emphasizing the multifaceted nature of supplement consumption. However, the existing literature on these associations remains limited, and further investigation is needed to better understand the underlying factors.
The participants’ most common motivation for PS use was to increase muscle mass, followed by muscle recovery and performance enhancement, which is consistent with the findings reported in the literature [15,27,36]. However, some studies report gender differences in supplement use motivations [27,36,37,38]. In our study, although gender was a predictor for PS use, we observed no significant gender-based variation in motivating reasons. These findings align with previous research focusing on athletes, which also highlighted that gender, level of competition, and sport type did not impact health reasons for supplement choice [39]. In the evaluations of supplement choice, protein powders were the preferred form of supplementation, with many participants consuming them post-workout (55%), and others using them pre- (20%) or peri-workout (19%). These patterns align with evidence supporting post-exercise protein intake for muscle synthesis and recovery, though debates about the optimal timing persist [40,41].
A notable proportion of the participants reported adverse effects such as nausea, dizziness, allergic reactions, and sleep disturbances, reflecting concerns raised by other studies [16,17,31]. However, these findings may be subject to biases, including self-report and selection bias, which could affect the accuracy and generalizability of the reported adverse effects and motivations. Future research should provide prospective designs and standardized measures, and adjust for potential confounders to strengthen causal inference and reduce bias. Interestingly, many participants believed PSs undergo regulatory processes similar to medications, reflecting misconceptions about supplement safety. This contrasts with the literature indicating variable regulatory controls across countries and the absence of stringent oversight in the supplement industry [22,42]. Half of the respondents engaging in multiple types of exercise believed PSs are beneficial for health, while most participants relied on non-professional sources such as social media and sports coaches for information, reflecting the global findings on limited engagement with HCPs for supplementation advice [15,24,31,43].
The findings of this study have to be seen in light of some limitations. The description of exercise intensity was based on each respondent’s self-perception, which may not accurately reflect the actual intensity of their exercise practices. The survey relied on self-reported data for PS use, motivations, and health perceptions, which may introduce bias or social desirability bias. Total dietary protein intake was not assessed, which could have influenced the participants’ protein supplementation choices. Future research should incorporate detailed assessments of both total dietary protein intake and protein types to clarify the relationship between baseline intake and supplementation patterns. Additionally, the study was conducted within a specific cultural context, and cultural differences may affect the generalizability of the findings to other populations. Future research should expand on these findings by incorporating more diverse and culturally varied samples to validate the results; reduce bias; and explore demographic patterns, motivational factors, and health perceptions across different populations and food cultures. Regardless of these limitations, this research provides a foundation for future studies, including randomized controlled trials, which can address these challenges and integrate PS use with safety considerations into the lifestyles of non-professional athletes. Despite its limitations, this study has several strengths. A key strength is the large sample size (n = 1100), which enhances the reliability of the findings and supports their generalizability within the studied population. However, future investigations should incorporate formal sample size calculations to ensure optimal study design. The current study provides novel insights into PS by examining demographic patterns such as gender, age, and motivational factors among non-professional athletes and general fitness practitioners, with limited evidence available from Greece. By incorporating the demographic, behavioral, and attitudinal factors, the study adds depth to the existing literature and highlights important trends, such as the reliance on informal information sources and misconceptions about supplement safety. Importantly, this research contributes to public health discussions by identifying areas where educational and regulatory interventions can promote safer and more informed PS practices.

4. Materials and Methods

4.1. Study Design and Ethics

This was a cross-sectional study using a questionnaire constructed based on gaps identified in the previous literature (Knapik et al., 2016) [32] and was adapted from a previously validated questionnaire (Sánchez et al., 2011) [44] designed to assess the patterns and perceptions of protein supplement use. A pilot test was conducted with a sample of 30 individuals from the target population in Greece to ensure clarity and relevance. The initial draft of the questions was reviewed and edited by non-professional athletes and fitness practitioners.
The questionnaire was available in printed form; consisted of closed-type and multiple-response questions; and was distributed in gyms, athletic organizations, amusement parks, and playing fields in two major cities in Greece (Athens and Thessaloniki). The gyms and athletic organizations were important sources for targeting individuals who practiced various athletic activities and expressed interest in PS use as part of their athletic performance. The questionnaire structure consisted of two main parts: The first part of the questionnaire collected demographic information, including gender; age; anthropometric data; educational level; occupation (including whether it was sports-related); place of residence; and lifestyle habits such smoking, frequency of exercise (”low”, “moderate”, or “hard”), and type of exercise (“fitness”, “aerobic”, “anaerobic”, or “mixed exercise”). This information was used to assess potential associations between participant characteristics and PS use. Additionally, it included a single question on the use of any type of dietary supplement (e.g., vitamins, minerals, fatty acids, probiotics, herbal extracts, amino acids, etc.), designed to capture overall dietary supplement usage. The second part of the questionnaire targeted only those who had used PSs as part of their diet for at least one year prior to their participation in the survey. It included questions concerning PS use, knowledge, and perceptions of PS, sources of information regarding PS usage, legal aspects of supplement consumption, and associated negative health consequences. The questionnaire required approximately twenty minutes to complete. Data collection took place from June 2023 to September 2023. The study protocol was approved by the ethics committee of the Democritus University of Thrace (Approval number 51760/469, Date: 9 June 2023).

4.2. Eligibility Criteria of Participants

An approximate sum of 2000 questionnaires were distributed in gyms, athletic organizations, amusement parks, and playing fields, aiming for a 50% success rate in responses. From the total of 1100 respondents, all the participants were adults (≥18 years old), Greek residents, non-professional athletes, and males or females; their answers were anonymous and voluntarily given following their consent. Professional athletes and people suffering from serious health conditions, such as musculoskeletal issues and injuries, were excluded from the study. The only requirement was that the participants would have been practicing a kind of physical exercise casually for at least 6 months before their participation in the survey.

4.3. Statistical Analysis

Descriptive statistical analysis was performed to describe the basic demographic features of the respondents, but also to assess their perception and views on benefits and potential health risks related to PS use by indicating frequencies, percentages, means, and associations. Chi-square tests were performed to assess whether differences in demographics such as age, gender, educational background, BMI, smoking habits, and occupation related to sports may affect the use patterns of PSs. Logistic regression analysis was performed to examine the impact of several independent variables and their potential association with the likelihood of PS use (Odds Ratio; CI 95%). The statistical analysis of the study was performed using IBM SPSS Statistics (version 29) for MacOS Sierra 10.12.3. The significance level was set to p < 0.05.

5. Conclusions

This study contributes to the growing body of research on PS consumption among non-professional athletes, a population that has been less extensively studied compared to elite athletes. Our findings highlight key demographic, behavioral, and motivational factors influencing PS use, reinforcing the trends observed in the previous literature. While PSs have recognized benefits, the reported side effects among PS users underscore the importance of consumer awareness and regulatory oversight. Despite the wide use of PSs, misconceptions persist regarding their regulation and safety, with many participants relying on non-professional information sources. This study emphasizes the need for targeted educational initiatives to improve awareness of safe PS practices among non-professional athletes and fitness practitioners. Regulatory bodies should consider strengthening supplement oversight to ensure product quality and accurate labeling. The findings underline the importance of HCPs in guiding supplement decisions and suggest the value of culturally tailored public health strategies. Future research, including longitudinal studies and randomized controlled trials, needs to further assess long-term health effects and the optimal use of PS in non-professional athletes.

Author Contributions

Conceptualization, C.K., A.P. and D.L.; methodology, C.K., G.-E.D. and P.A.; software, E.D.; validation, P.K., K.P., G.K. and P.B.; formal analysis, P.K., K.P., G.K., P.B., G.-E.D. and P.A.; investigation, P.A. and P.B.; data curation, P.K. and K.P.; writing—original draft preparation, G.-E.D., P.A., C.K. and E.D.; writing—review and editing, P.A., G.-E.D. and K.P.; visualization, E.D.; supervision, C.K., A.P. and D.L.; funding acquisition, K.P. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Institutional Review Board Statement

The study protocol was approved by the ethics committee of the Democritus University of Thrace (Approval number 51760/469, Date: 9 June 2023).

Informed Consent Statement

All data were collected anonymously and voluntarily, and informed consent was obtained from all subjects involved in the study.

Data Availability Statement

All relevant data summarized in this study are available upon request from the principal investigator, Assistant Prof. Christos Kontogiorgis.

Conflicts of Interest

The authors declare no conflict of interest.

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Physiologia 05 00018 g001
Figure 1. Predictors for protein supplement use. p-values reflect the significant outcomes (p < 0.05) *; (p < 0.01) **.
Figure 1. Predictors for protein supplement use. p-values reflect the significant outcomes (p < 0.05) *; (p < 0.01) **.
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Figure 2. Distribution of reasons for protein supplement intake according to users’ views.
Figure 2. Distribution of reasons for protein supplement intake according to users’ views.
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Figure 3. Self-reported preferred timing for protein supplement consumption.
Figure 3. Self-reported preferred timing for protein supplement consumption.
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Figure 4. Preferred type of protein supplement by sex, age group (A), and PA type (B) (distribution of positive responses).
Figure 4. Preferred type of protein supplement by sex, age group (A), and PA type (B) (distribution of positive responses).
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Figure 5. Self-reported side effects (orange—Dark: male/Light: Female) and disclosure of visiting a medical doctor due to these side effects (blue—Dark: male/Light: Female).
Figure 5. Self-reported side effects (orange—Dark: male/Light: Female) and disclosure of visiting a medical doctor due to these side effects (blue—Dark: male/Light: Female).
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Table 1. Demographic characteristics and protein supplement (PS) use.
Table 1. Demographic characteristics and protein supplement (PS) use.
FemaleMale
Age (years)
18–24149 (22.5)113 (25.5)
25–34253 (38.3)206 (46.9)
35–4479 (12.0)91 (20.7)
45–6546 (7.0)29 (6.6)
BMI (kg/m2)
<18.432 (4.8)1 (0.2)
18.5–24.9483 (73.1)208 (47.4)
25–29.9112 (16.9)194 (44.2)
30–34.928 (4.2)29 (6.6)
35–39.96 (0.9)7 (1.6)
BMI (kg/m2)
Mean ± SD		22.5 ± 3.6425.56 ± 3.34
Protein Supplement Use, N (%)
Total
1100 (100)		Yes
327 (30)		No
773 (70)		p-value
Gender <0.001 *
Male439 (40)203 (62)236 (31)
Female661 (60)124 (38)537 (69)
Age (years) <0.001 *
18–24396 (36)98 (30)298 (39)
25–34459 (42)136 (42)323 (42)
35–44170 (15)71 (22)99 (13)
45–6575 (7)22 (6)53 (6)
BMI (kg/m2) <0.001*
<18.433 (3)7 (2)26 (3)
18.5–24.9691 (63)189 (58)502 (65)
25–29.9306 (28)120 (36)186 (24)
30–34.957 (5)9 (3)48 (6)
35–39.913 (1)2 (1)11 (2)
Education 0.170
Secondary404 (37)117 (36)287 (37)
Undergraduate522 (47)148 (45)374 (48)
Postgraduate174 (16)62 (19)112 (15)
Work related to sports <0.001 *
Yes262 (24)100(31)162 (21)
No838 (76)227(69)611 (79)
Smoking 0.020 *
Yes378 (34)98 (30)280 (36)
No722 (66)229 (70)493 (64)
BMI: body mass index; *: p-values reflect the significant outcomes of Chi-square or regression analysis for binary or multiple response variables, respectively.
Table 2. Associations between reasons for PS use to participants’ characteristics (Cramer’s V value).
Table 2. Associations between reasons for PS use to participants’ characteristics (Cramer’s V value).
Energy_IncreaseMass_IncreaseAestheticsPerformance_ImprovementWeight_LossMuscle_Recovery
Age_Groups0.0650.0630.0860.0970.1090.183
BMI_Groups0.1160.1140.0550.2020.1670.155
Gender0.0230.0680.0210.0580.0350.047
Age_25–340.1800.1200.1700.1600.2000.120
Age_35–440.3000.2700.1100.3300.2800.280
BMI_18.5–24.90.1900.1400.1600.2000.1800.220
BMI_25–29.90.1200.1200.0300.0600.1800.240
Males0.1900.1400.1600.2000.1700.220
Note: calculations were not included for a number of responses <20. Positive responses to at least one of the reasons for PS use were included in this analysis. The colour represents the lower (light blue) and the higher correlation (dark blue).
Table 3. Preferred channels of information about PSs and users’ perception of PS safety control regulations associated with exercise types.
Table 3. Preferred channels of information about PSs and users’ perception of PS safety control regulations associated with exercise types.
Source of information about PSsp-value
Exercise typeHCPsSocial Media/Websites/ForumsFriends/relativesCoach/Gym0.005 *
Moderate exercise4 (8.7%)8 (6.4%)3 (9.7%)4 (3.2%)
Fitness13 (28.3%)50 (40%)12 (38.7%)54 (43.2%)
Aerobic4 (8.7%)5 (4%)8 (25.8%)16 (12.8%)
Anaerobic7 (15.2%)17 (13.6%)0 (0%)22 (17.6%)
Mixed exercise18 (39.1%)45 (36%)8 (25.8%)29 (23.2%)
Are PSs controlled by authorities for safety with a similar process to medications?
Exercise typeYesNo0.02 *
Low/moderate level7 (37%)12 (63%)
Fitness78 (60%)52 (40%)
Aerobic18 (55%)15 (46%)
Anaerobic16 (35%)30 (65%)
Mixed exercise52 (52%)48 (48%)
Work related to sportsYesNo0.01 *
Yes62 (62%)38 (38%)
No109 (48%)119 (52%)
PS: protein supplementation; HCP: healthcare professionals; *: p-values reflect the outcomes of Chi-square or regression analysis for binary or multiple response variables, respectively.
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Athanasopoulou, P.; Deligiannidou, G.-E.; Basdeki, P.; Deligianni, E.; Kryοna, P.; Kaltsos, G.; Lazari, D.; Papadopoulos, A.; Papadimitriou, K.; Kontogiorgis, C. Trends in Protein Supplement Use Among Non-Professional Athletes: Insights from a Survey in Greece. Physiologia 2025, 5, 18. https://doi.org/10.3390/physiologia5020018

AMA Style

Athanasopoulou P, Deligiannidou G-E, Basdeki P, Deligianni E, Kryοna P, Kaltsos G, Lazari D, Papadopoulos A, Papadimitriou K, Kontogiorgis C. Trends in Protein Supplement Use Among Non-Professional Athletes: Insights from a Survey in Greece. Physiologia. 2025; 5(2):18. https://doi.org/10.3390/physiologia5020018

Chicago/Turabian Style

Athanasopoulou, Panagiota, Georgia-Eirini Deligiannidou, Paraskevi Basdeki, Elena Deligianni, Pinelopi Kryοna, Georgios Kaltsos, Diamanto Lazari, Athanasios Papadopoulos, Konstantinos Papadimitriou, and Christos Kontogiorgis. 2025. "Trends in Protein Supplement Use Among Non-Professional Athletes: Insights from a Survey in Greece" Physiologia 5, no. 2: 18. https://doi.org/10.3390/physiologia5020018

APA Style

Athanasopoulou, P., Deligiannidou, G.-E., Basdeki, P., Deligianni, E., Kryοna, P., Kaltsos, G., Lazari, D., Papadopoulos, A., Papadimitriou, K., & Kontogiorgis, C. (2025). Trends in Protein Supplement Use Among Non-Professional Athletes: Insights from a Survey in Greece. Physiologia, 5(2), 18. https://doi.org/10.3390/physiologia5020018

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