Consumption and knowledge of protein supplements in the Spanish adult population: A cross-sectional survey-based study

Abstract

Introduction

The popularity of protein supplements (PS) has increased significantly in recent years. Their use is often undertaken without the supervision of a healthcare professional, which may lead to excessive or inappropriate intake and, consequently, pose a health risk.

Objective

To assess knowledge and consumption habits regarding PS among the Spanish population.

Material and methods

A cross-sectional observational study was conducted using a digital questionnaire (Google Forms®) among 168 participants aged 15–70 years.

Results

Overall, 35.7% of respondents reported consuming PS, with increasing muscle mass being the main reason for consumption among 66.7% of these participants. Although 100% of participants recognised the risks associated with excessive consumption, 26.2% were unaware of the existence of maximum recommended intakes. Among those who were aware of these limits, most believed that the maximum intake was above 30 g of PS per day.

Discussion

There is a substantial gap between PS consumption and knowledge of safe intake levels. These findings highlight the need to strengthen the role of community pharmacists as key healthcare professionals in promoting the rational and safe use of PS.

Introduction

Protein supplements (PS) are a type of food supplement (FS) used primarily to supplement the diet by providing an additional source of protein. Their users include population groups with increased protein requirements (older adults, athletes, patients with conditions associated with greater loss of muscle mass or increased protein needs), as well as people who use them for the beneficial effects associated with their consumption despite there being no nutritional need for them [1].

Both the food and pharmaceutical industries have identified protein supplements as an opportunity for growth, with the global market estimated to increase progressively from USD 32.72 billion in 2025 to USD 49.29 billion in 2030 [2]. The industry has also had to continually reinvent itself in order to meet consumer needs. This has led to the use of new plant-based protein sources, particularly soy and pea protein, in the manufacture of these PS [3,4].

In addition to protein, PS provide variable amounts of essential elements (sodium, potassium, calcium, magnesium, molybdenum, manganese, copper, iron, zinc, chromium and cobalt) and potentially toxic elements (nickel, strontium, barium, aluminium, cadmium, boron, vanadium and lead), which at high concentrations may pose a risk to consumers’ health, although users are generally unaware of their presence [5-9].

Current legislation does not specifically address PS, but rather food supplements in general. At European level, Regulation (EC) No 1170/2009, and at national level, Royal Decree 130/2018, specify the minerals that may be added to these FS, but not the permitted amounts [10,11]. Furthermore, there is no legislation specifying the maximum concentrations of essential or potentially toxic elements that may be present in these products, except for lead (3 mg Pb/kg PS) and cadmium (1 mg Cd/kg PS) [12].

For this reason, the population needs to be aware of the risks associated with excessive consumption of these PS. It is also essential that these products are obtained from healthcare establishments, such as community pharmacies, where pharmacists can provide individualised advice to support appropriate product selection and prevent possible adverse effects.

Materials and methods

An observational, descriptive, cross-sectional study was conducted using a questionnaire consisting of 21 questions (Appendix 1), designed to assess the general population’s knowledge of FS, with particular emphasis on PS, and to analyse their consumption habits.

The questionnaire was distributed digitally through the Google Forms® platform and was completed by 168 participants aged between 15 and 70 years, of whom 112 were women. Participation was voluntary and anonymous.

The questionnaire made it possible to analyse patterns of FS and PS consumption according to different sociodemographic and lifestyle variables, including age, sex, employment status and physical activity.

Results

A total of 168 valid responses were obtained, of which 66.7% (N=112) were from women and 33.3% (N=56) from men aged between 15 and 70 years. Sixty per cent of participants were aged between 19 and 35 years (Figure 1).

Figure 1. Percentage distribution of participants by age group.

Results are expressed as a percentage of all participants (N=168).

Most respondents (78.6%) were living in the Canary Islands at the time of completing the questionnaire, followed by the Community of Madrid (11.9%) and other Autonomous Communities, including the Valencian Community (4.8%), Andalusia (2.4%) and Galicia (2.4%), which accounted for fewer participants (Figure 2).

Figure 2. Autonomous Communities in which respondents reside.

Absolute frequency of respondents (n=168) classified by Autonomous Community of residence. The Canary Islands accounted for the majority of participants (n=132), followed by the Community of Madrid (n=20), the Valencian Community (n=8), Andalusia (n=4) and Galicia (n=4).

Regarding the employment status of the study population, 61.9% were employed (N=104), 28.6% were students (N=48), 4.8% were unemployed (N=8) and the remaining 4.8% were retired (N=8).

Of all respondents, 83.4% (N=140) reported engaging in some form of physical activity at varying frequencies. The largest groups were those who exercised three to five times per week (28.6%) and those who exercised fewer than three days per week (28.6%). They were followed by participants who exercised five days per week (14.3%), while the smallest group (11.9%) exercised daily (Figure 3).

Figure 3. Frequency of physical exercise among respondents.

Absolute number of responses (n=168) grouped according to weekly frequency of physical activity. Participants exercising 3-5 days per week (n=48) and fewer than 3 days per week (n=48) predominated, followed by those who did not exercise on any day (n=28), those exercising 5 days per week (n=24) and those exercising daily (n=20).

Regarding FS consumption, 57.1% of participants reported that they did not use them, whereas 42.9% did. Among users, PS were the most commonly consumed (50%), followed by vitamin supplements (38.9%) and, to a lesser extent, mineral supplements (11.1%).

Regarding knowledge of PS, 95.2% of respondents considered that it was not necessary for the entire population to consume these products to enrich their diet, and only 11.1% believed that PS could be used as meal replacements.

All respondents stated that excessive PS consumption may pose a health risk. However, 26.2% believed that there was no recommended maximum daily intake. Although 73.8% believed that such a maximum intake existed, 46% considered it to be greater than 30 g of PS per day, the maximum intake recommended by the manufacturers of these products (Figure 4).

Figure 4. Maximum PS intake considered appropriate by respondents.

Percentage distribution of responses regarding the recommended daily amount of PS (n=60). Thirty-nine per cent estimated a limit of 60 g/day, 36% a limit of 30 g/day, 18% a limit of 10 g/day and 7% a limit of 100 g/day.

Regarding respondents’ consumption habits, 35.7% (N=60) reported consuming some type of PS at the time of the survey (Figure 5).

Figure 5. Flow chart of study sample selection.

Schematic representation of participant screening from the total surveyed population (n=168) to the subsample of FS consumers in general (n=72) and the specific subsample of protein supplement consumers (n=60).

The main motivation was increasing muscle mass (66.7%), followed by replacing a daily meal (11.1%), using them because they were fashionable products (11.1%) and other unspecified motivations (11.1%). Recommendations to begin consuming these products came from various sources, including personal trainers, people in the respondents’ social environment, social media and healthcare professionals, among others (Figure 6).

Figure 6. Motivation for PS consumption.

Percentage distribution of PS consumers according to the person or source that recommended their use (n=60). Personal trainers were the main source of recommendation (40%), followed by social media (30%), people in the respondent’s close social environment (10%), healthcare professionals (10%) and self-prescription or “nobody” (10%).

PS can be purchased through different distribution channels. Most respondents bought them from specialist shops, while a minority purchased them from healthcare establishments such as pharmacies (Figure 7).

Figure 7. Place of purchase of PS.

Absolute frequency of responses (n=60) according to the point of sale or distribution channel used by PS consumers. Specialist shops were the main place of purchase (n=46), followed by supermarkets (n=4), gyms (n=4), sports shops (n=3) and pharmacies (n=3).

Sixty per cent of PS users (N=36) consumed these products daily, whereas 20% (N=12) consumed them only on days when they exercised, in the form of pre- or post-workout shakes. Greater variability was observed when respondents were asked about the quantities consumed each day: most consumed 60 g of PS daily, followed by 90 g/day (Figure 8).

Figure 8. Daily amount of PS consumed.

Percentage distribution of the daily intake reported by respondents who consumed PS (n=60). Half of users (50%) reported consuming 60 g/day, followed by 20% consuming <30 g/day, 20% consuming 90 g/day and 10% consuming 30 g/day.

Discussion

The results of the present study show that PS consumption is widespread among the surveyed population. Most responses came from the 19-35-year age group, which corresponds to stages of life in which there is greater interest in improving body composition, physical performance and appearance. However, the data indicate that use of these products is not limited exclusively to high-performance athletes, but is also observed among diverse population profiles with different levels of physical activity and reasons for consumption, reflecting the increasing normalisation of these products in the habitual diet.

Regarding consumption patterns, PS were the type of FS most commonly used by participants, ahead of vitamin and mineral supplements. This finding is consistent with the sustained growth of the global PS market in recent years, driven both by expansion of the sports sector and by the increase in commercial availability and the widespread perception of these products as safe and beneficial to health [2]. However, this positive perception contrasts with the limited knowledge observed among the population regarding recommended maximum doses and appropriate amounts for daily consumption.

Although most respondents were aware that excessive PS consumption may pose a health risk, a substantial proportion of participants were unaware of the maximum intake recommended by the industry. This was reflected in their reported consumption habits, as a considerable proportion of users stated that they consumed amounts above the recommended levels on a daily basis. These findings suggest that PS consumers have a limited perception of the risks associated with their use, focusing primarily on the potential consequences of excessive protein intake, while being less aware of exposure to essential and potentially toxic elements present at variable concentrations in these products.

Another relevant finding was that PS were predominantly purchased outside healthcare establishments, mainly from specialist shops or through other sales channels in which healthcare professionals are not involved. This purchasing pattern may encourage consumption without professional advice, increasing the likelihood of inappropriate or unnecessary use or use that is not adapted to the individual needs of the consumer. In this regard, the limited involvement of healthcare professionals in the initial recommendation of these products highlights the need to strengthen health education strategies aimed at the general population.

These findings also reinforce the role of community pharmacists as key healthcare professionals in promoting the rational use of food supplements, particularly PS. Community pharmacies can provide individualised advice on indication, appropriate doses, duration of use, possible interactions and associated risks, thereby improving public knowledge and helping to prevent inappropriate consumption practices. Active involvement of community pharmacists in health education programmes could also encourage the purchase of these products through more closely supervised healthcare channels, facilitate more appropriate follow-up of consumers, and highlight pharmacists’ strategic role in the design and implementation of risk communication campaigns for the public. Such initiatives could improve knowledge of recommended intakes, the potential risks associated with consumption, and the need for individualised and supervised use of PS and other FS.

Appendix 1. Survey on protein supplement consumption and knowledge

Appendix 1. Survey on protein supplement consumption and knowledge (PDF).

Funding Statement

This research received no external funding.