4.1. Sustainability and Food Sustainability Knowledge
After analyzing the knowledge level regarding sustainability and food sustainability among both white- and blue-collar employees, we found that all participants exhibited the highest levels of knowledge on topics such as “local food”, “environmental impact”, and “biodiversity”. Nevertheless, their knowledge of “green water/blue water” was extremely inadequate. The term “blue water” refers to surface and groundwater, whereas “green water” denotes rainwater retained in the soil as soil moisture. Green water constitutes the majority part of water used throughout agricultural production processes [
24]. The participants, like those in the original study conducted in Spain, demonstrated the highest level of knowledge of the terms of “environmental impact” and “local food”, while they exhibited the lowest level of knowledge with the term “green water/blue water” [
17]. Presently, “ecological footprint”, “carbon footprint”, and “water footprint” are the most used concepts in the media, particularly in social media, to raise awareness about sustainability. Nevertheless, the lack of detailed emphasis on the water footprint component is concerning. Promoting the use of local foods to reduce the environmental impact and carbon footprint and emphasizing the need to protect biodiversity to ensure sustainability could potentially enhance the societal awareness of these concepts. In addition, for eight concepts related to sustainability and food sustainability, the knowledge level of white-collar employees was expected to be statistically significantly higher than that of blue-collar employees (
p < 0.05), and this situation can be associated with the high education and sociocultural levels of white-collar employees.
The level of knowledge on the concept of “food sustainability” among both white-collar and blue-collar employees was 30.5%. In contrast to our study, the original Spanish study declared that over 50.0% of the participants comprehended the term “food sustainability” [
17]. A study in Turkey found that 24.3% of participants were knowledgeable about the concept of “sustainable nutrition” [
25], whereas another study found that 21.1% of participants had only heard of it [
26]. These findings are believed to be correlated with the delayed introduction and awareness of the subject of sustainability in our country in comparison to European countries.
In 2010, the Food and Agriculture Organization (FAO) established a definition for sustainable diets. These diets are characterized by their low impact on the environment while also promoting food and nutrition security and supporting the health and well-being of current and future generations. It is also said that sustainable diets are protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair, affordable, nutritionally adequate, safe, and healthy while optimizing natural and human resources [
27]. The participants were asked to rate the importance of a list of attributes which can be used to define a sustainable diet. The blue-collar employees gave lower scores than the white-collar employees to items associated with environment health. The increased level of education and associated knowledge about environment health issues among white-collar employees might explain this occurrence. The most important attribute of a sustainable diet for all participants was the “diet is affordable”, while the least important attribute was a “low environmental impact”. All participants determined the availability of access and suitability as the most significant criteria in defining sustainable nutrition, which highlights the essential role of the social aspect of sustainable nutrition in Turkish society.
When all participants were asked about the impact of different food groups on sustainability, over 80% said that “vegetables” contribute positively to planetary health in terms of sustainability. Conversely, over 90% of participants indicated that “processed foods” and “sodas and processed drinks” had negative impacts. More than half of the participants expressed that “meat and derivates”, “fish and derivates”, “milk and dairy”, and “eggs” had beneficial effects on planetary health. Consistent with this study, 85% of the participants in the original study conducted in Spain said that “vegetables” contribute positively to the health of the planet, while 87% reported that “processed foods” and 82% declared that “soda and processed drinks” had negative effects. Additionally, over 50% of the participants expressed that “meat and derivatives”, “fish and derivatives”, “milk and dairy”, and “eggs” had beneficial effects on planetary health [
17]. According to this study’s results, it is generally accepted in society that vegetables and fruits are the primary food groups for a sustainable diet, whereas processed foods and drinks have a damaging impact on sustainability. Nevertheless, there is a lack of information regarding the impacts of animal-based foods on sustainability. Plant-based foods have significantly less negative environmental impact than animal-based foods. Even plant-based foods, vegetables, and grains with the highest environmental impacts cause less environmental damage than meat and dairy products with the lowest impact [
28]. Life cycle assessment studies have shown that pork, chicken, and seafood produce less greenhouse gas emissions than beef; however, even the lowest-impact animal-based products exceed the average greenhouse gas emissions of substitute plant proteins [
29]. For developed countries, reducing red meat consumption is crucial to achieving emission targets, and shifting to animal-free diets has the potential to reduce global greenhouse gas emissions by 49% [
30]. In addition, although seafood is considered a low-environmental-impact source of animal protein, 60% of the world’s fish stocks have been completely captured, and more than 30% are currently overfished, overtaxing marine systems [
31]. Sustainable resource management is critical to ensuring the long-term viability of biodiversity and ecosystems on which societies depend. The accurate measurement of the supply of and demand for natural resources is the key to their effective management [
32].
According to the results regarding the importance of water use in food production, the white-collar employees stated that more water is needed to grow animal-based foods than blue-collar employees, while the blue-collar employees stated the opposite. This situation can again be explained by the fact that white-collar employees have a higher level of education than blue-collar employees and therefore have more knowledge about planetary health and sustainability. Global agriculture accounts for 70% of the freshwater extracted for human use. Moreover, when we consider that approximately half of all grains grown worldwide are used as animal feed, the increasing demand for meat and dairy products has direct effects on land and water use [
28]. A study found that the water footprint of 1 kg of beef is sixty-one times higher than the water footprint of the same amount of vegetables and eleven times higher than the water footprint of pasta [
33]. Another study found that 3.8 m
2 of land, 2.5 m
3 of water, 39 g of fertilizer, and 2.2 g of pesticides are required to produce 1 kg of beans and that 52 m
2 of land, 20.2 m
3 of water, 360 g of fertilizer, and 17.2 g of pesticides are required to produce the same amount of beef [
34]. The UN’s 2011 World Economic and Social Survey concluded that intensive livestock production is the largest source of sector-specific water pollution [
35]. In addition, the fact that the mean scores in our study comparing the amount of water required to produce plant-based and animal-based foods are very close to each other shows that this information has not fully reached the general public.
4.3. The Mediterranean Diet Adherence
The MD is a dietary pattern that involves consuming a significant amount of vegetables, fruits, whole-grain bread, whole-grain rice, pulses, and nuts. It also includes moderate amounts of fish and dairy products, particularly cheese and yogurt. However, it restricts the consumption of red meat and emphasizes the use of virgin olive oil as the main source of fat [
38,
39]. The MD involves not only a variety of foods but also a cultural model that encompasses the selection, production, processing, and distribution of these foods. The Mediterranean diet is not only shown as a cultural concept but also as a healthy and environmentally friendly model [
40]. A study investigating the effects of different diet models on the environment found that while a vegan diet has a high health score and is sustainable, an environmentally friendly diet that reduces the consumption of animal-based foods, such as MD, is a more acceptable option for society as a whole [
41]. Another study in Spain showed that switching to a MD would reduce the environmental impact (−72%), land use (−58%), and energy (−52%) and water (−33%) consumption [
42]. It was also reported that the reduced consumption of processed foods in the MD reduces plastic consumption and the emissions associated with processing, packaging, and transporting these products. It was stated that a more climate-friendly approach can easily be adopted by focusing on consuming seasonal, locally sourced, and sustainably harvested and processed ingredients to further reduce emissions while following the MD [
43]. Overall, the MD is described as a potential sustainable diet model [
44].
When we evaluated the participants’ adherence to the MD, the mean score was 5.4 ± 1.90, and the mean score of white-collar employees was statistically significantly higher than that of blue-collar employees. Based on the MEDAS classification, all individuals exhibited non-adherence to the MD at a frequency of 74.8%, moderate adherence at 18.1%, and high adherence at 7.1%. Notably, white-collar employees were the only ones who highly followed the MD, with only four blue-collar employees showing moderate adherence. Other studies on MD adherence conducted in our country revealed a low rate of participants with high adherence, whereas our study revealed a high rate of moderate adherence [
45,
46]. It is thought that the main reason for this difference is that half of this study’s sample consisted of blue-collar employees with low socioeconomic, cultural, and educational levels. Another study conducted in our country assessed highly educated individuals’ adherence to the MD. Moderate adherence to the MD among individuals was similar to that of white-collar employees in our study [
47].
4.4. The Association between the Mediterranean Diet Adherence, Sustainability Knowledge, Sustainable Eating Attitude, Age, Anthropometric Measurements, and Nutrient Intake
The participants’ MEDAS scores were low in this study; however, the positive relationship between the MEDAS score and the Sustainable Diet Definition score and Sustainable Eating Attitude score emerged as one of this study’s important outcomes. In accordance with our study, some studies in our country found correlations between the level of adherence to the MD and an increase in awareness of the ecological footprint, which is a component of sustainability [
48,
49]. On the other hand, no significant correlation was found between Water Use Importance score and MEDAS score, age, and anthropometric measurements. Animal-based products have a significantly larger water footprint than plant products with equivalent nutritional and energy value; therefore, substituting animal products with nutritionally equivalent plant-based products can reduce the water footprint [
50]. One study reported that replacing animal-based diets with nutritionally equivalent plant-based diets will reduce the water footprint by 36% in developed countries and 15% in developing countries [
51]. Nevertheless, this information was not released to the general population, since our findings indicated that all participants showed comparable assessments of the water requirements for producing plant-based versus animal-based foods (2.1 ± 1.79 and 1.8 ± 1.67, respectively). Therefore, it is thought that there is no significant correlation between the Water Use Importance score and other variables. In addition, body weight, BMI, waist circumference, and PBF were associated with low MEDAS and Sustainable Eating Attitude scores.
Overweight and obesity are significant global public health problems. In recent decades, there has been a significant increase in the worldwide occurrence of overweight and obesity, and this trend will likely continue [
52]. The World Health Organization (WHO) states that Turkey has the highest obesity percentage among adults in Europe, standing at 32.1%, while the rest of Europe has a rate of 23.3% [
53]. Within this study, 56.2% of the participants notably showed an attribute that classified them as being overweight or obese. Observational studies have shown that adopting sustainable healthy eating patterns is linked to a reduced risk of overweight and/or obesity [
48,
54,
55]. Consequently, more studies are required to investigate the impact of obesity on the long-term sustainability of the environment and the effects of sustainable diets on the prevalence of obesity. The MD is a dietary pattern that involves consuming a considerable amount of dietary fiber [
56]. In our study, no relationship was found between dietary fiber and MEDAS score, showing the generally low adherence of our population to the MD.
Another significant outcome of this study is the positive relationship between MEDAS score and plant-based protein, MUFA, and omega-3 PUFA intake and a negative relationship between MEDAS score, SFA, and omega-6/omega-3 ratio. Olive oil is the most characteristic attribute of the MD. Hence, while this result was expected, the relatively low frequency of high adherence to the MD in the sample (7.1%) could be attributed to the higher cost of olive oil compared to alternative vegetable oils.
The dietary intake of omega-3 and omega-6 fatty acids is considered crucial in the prevention and development of chronic disorders. Omega-3 polyunsaturated fatty acids are known to have beneficial effects on health through their anti-inflammatory, antioxidant, and antilipidemic actions [
57]. The recommended ratio of omega-6/omega-3 fatty acids for optimal health benefits is in the range of 1:1–2:1. Nevertheless, due to industrialization, the typical Western diet may have substantially elevated this ratio, reaching up to 20:1 [
58]. The MD emphasizes the consumption of locally sourced and seasonal seafood, making it a healthy choice with a minimal environmental impact [
59]. Therefore, it is expected that a high adherence to the MD has a positive correlation with omega-3 intake and a negative correlation with the omega-6/omega-3 ratio. Nevertheless, the literature does not provide a definitive understanding of the influence of seafood on a sustainable diet. Despite the high health benefits of seafood consumption and its lower impact on greenhouse gas emissions compared to other animal-based proteins, it is important to consider that marine systems are under stress due to the complete capture of 60% of the world’s fish stocks and overfishing of more than 30% [
31].
Multiple mechanisms could explain the beneficial effect of omega-3 fatty acids. Overall, their capacity to decrease fat synthesis in adipose tissue and their potential for reducing low-grade inflammation through their anti-inflammatory characteristics may prove effective in weight management [
57]. One of the most important dietary factors in preventing obesity is a stable omega-6/omega-3 ratio, and a lower omega-6/omega-3 ratio should be adhered to for the management of obesity. While a high omega-6 fatty acid intake and a high omega-6/omega-3 ratio are associated with weight gain in both animal and human studies, it is reported that a high omega-6 fatty acid intake reduces the risk of weight gain [
57,
58,
60]. Hence, the negative correlation of BMI with omega-3 intake and the positive correlation with the omega-6/omega-3 ratio were expected and are significant outcomes of this study. The impact of MUFAs on inflammation is not well documented; however, an increasing amount of research is establishing an association between MUFAs and anti-inflammatory diseases [
61]. Obesity is a significant component of the metabolic syndrome and is frequently associated with chronic inflammation [
62]. This study revealed a negative correlation between MUFA intake and BMI, suggesting that MUFAs may play a significant role in managing obesity.
Finally, one of the most important results of this study is the negative correlation between plant-based protein consumption and BMI, an important component of both environmental and human health. Plant-based diets include any dietary patterns that promote consuming plenty of plant-based foods while restricting or reducing the consumption of animal-based products. Plant-based diets, such as vegetarianism and veganism, are typically characterized by the types of food they eliminate rather than include [
26]. Multiple studies examining various dietary patterns consistently found that diets that limit meat consumption, including plant-based and vegan diets, are linked to improved health outcomes; decreased greenhouse gas emissions; and reduced use of land, energy, and water [
63,
64,
65]. Vegans who adhere to a well-balanced diet that achieves their bodies’ essential nutritional requirements have a reduced likelihood of developing obesity, hypertension, cardiovascular disease, diabetes, arthritis, cancer (particularly colon and prostate cancers), and fatal ischemic heart disease. This is due to the presence of protective compounds in fruits, vegetables, legumes, seaweed, oilseeds, whole grains, vegetable oils, and other plant-based foods [
66]. Nevertheless, vegans are at risk of lacking omega-3 fatty acids; iron; calcium; vitamins B12, B2, and B3; zinc; vitamin D; and iodine due to their diets being based on plant protein. These deficiencies can potentially harm the maintenance of an adequate immune system [
67]. As a result, it is extremely important that nutrition messages focus on consuming animal-based foods in moderation rather than strictly eliminating them from the diet to improve environmental and human health. To develop national plans and policies on sustainable nutrition, it is crucial to determine the public’s level of knowledge about sustainable nutrition and to evaluate their behaviors. This study shows that the public has a lack of knowledge about sustainability and sustainable nutrition and that their compliance with the Mediterranean diet is quite low.
Strengths and Limitations
One of this study’s strengths is its examination of the public’s level of knowledge and awareness on the subject with the aim of enhancing planetary and public health, a globally significant issue. This study was the first in Turkey to employ the validated and reliable Questionnaire on Food Sustainability Knowledge and Attitudes to Sustainable Eating. We evaluated not only sustainability knowledge and attitude levels but also compliance with the Mediterranean diet, one of the sustainable nutrition models. Additionally, we collected 24 h retrospective dietary records from the participants to enhance the validity of data on their consumption of sustainable nutrition components. We selected both white-collar and blue-collar employees for our sample, considering that the level of knowledge is proportional to the level of education. However, this study has a limitation: due to its voluntary nature, obtaining 24 h dietary records and body composition measurements from the participants was difficult. This prevented the sample size from increasing. We anticipate that the results of studies conducted on this subject with larger samples will incorporate the nutritional aspect into corporate sustainability policies.