The Mediterranean Diet in the Era of Climate Change: A Reference Diet for Human and Planetary Health

Abstract

Nowadays, climate change constitutes an enormous global threat for human health and environmental sustainability. The expanding world population and the increased global need for food production have an important negative impact upon the environment. Diet can link human health with environmental sustainability. Food production systems are closely related to anthropogenic greenhouse gas emissions and the aggravation of climate change, and current Western-type, animal-based dietary patterns may lead to adverse environmental footprints. In this present narrative review, we address the interconnection of the Mediterranean diet (MD) with climate change and sustainability. The MD is a highly recommended dietary intervention for the prevention and management of various endocrine and cardiometabolic diseases. Beyond its evidence-based, health-promoting effects, it also has a beneficial environmental impact, reducing greenhouse gas emissions and enhancing biodiversity, food security, and sustainability. Based on the evidence reviewed herein, the MD should be incorporated within the framework of a “One Health” model, which involves the improvement not only of human health but also of planetary health and food system sustainability. Our review aims to provide a stimulus for health professionals to strongly recommend the implementation of the MD under the current pressure of climate change, despite all barriers, targeting both human health preservation and planetary well-being.

1. Introduction

In ancient Greek times, Hippocrates was one of the first scientists who emphasized the importance of the interconnection between environmental conditions and certain types of diseases. He believed in the need to live in harmony with nature in order to maintain good physical and mental health. According to Hippocrates, “Human health does not depend solely on physiology, but is also in close interaction with the external environment in which humans live, as it may significantly affect their proportions in the human body”. In order to create a strong bond between humans and their environment, it is crucial to ensure a healthy, safe diet and sufficient food resources for the constantly growing population [1].

The globally increased need for food consumption plays a fundamental role in the detrimental effects of climate change (CC). CC has been related to a reduction in biodiversity, the depletion of natural resources, and the other adverse environmental impacts induced by modern households [2]. It has been predicted that the increasingly harsh phenomena of global CC will gradually decrease both food security and diet quality and will reduce water availability, ecosystem biodiversity, and the nutritional value of foods. This will occur mainly due to the impoverishment of the soil, combined with the expected continuous increase in food requests [3]. CC will ultimately affect the sustainability of food production systems by directly impacting crop yields, nutrient composition, and bioavailability, leading vulnerable populations to malnourishment and undernutrition [4]. These ominous data highlight the urgent need to take measures to improve food system sustainability. Relevant studies have shown that food production systems account for up to 37% of anthropogenic greenhouse gas emissions (GHGs) and 70% of freshwater use on a global scale [5,6]. The shift of current dietary habits to more sustainable food systems has been proposed as an effective measure to reach global GHG emission reduction targets and contribute to the decarbonization of the European continent by the year 2050 [7].

A large body of solid scientific evidence strongly recommends the adoption of plant-based dietary patterns for both human and planetary health promotion [8,9]. It has been consistently shown that plant-based dietary patterns contribute to a healthier diet and to a reduction in environmental impacts through lower GHG emissions and resource consumption [10]. A systematic review of the meta-analyses of prospective studies that examined the association between the incidence of cardiovascular disease (CVD) and certain types of food groups concluded that a dietary pattern oriented more around plant-derived foods is able to optimize CVD prevention [5]. Unfortunately, within the last 50 years, a dramatic change in dietary patterns has been observed, mainly characterized by the increased consumption of animal-based products and an over-consumption of high-fat energy-dense foods, leading to poor population health and negative environmental footprints [11]. Dietary patterns of poor quality represent the main risk factor for the development of non-communicable diet-related diseases, such as obesity, type 2 diabetes mellitus (T2DM), malignancies, and CVD, accounting for approximately 41 million deaths each year globally [5,12].

Several studies and reviews acknowledge the Mediterranean diet (MD), a world-renowned healthy diet, as a reference diet in terms of sustainability and environmental impact [8,13,14,15,16]. The Mediterranean dietary pattern (MDP) as a whole may serve as the outstanding model of a sustainable and environment-friendly nutritional system. In addition to its well-established beneficial effects on human health and chronic disease prevention and management, the MDP fulfils all those qualitative requirements that make it a sustainable diet with an essential role for CC and environmental stability [8,17,18]. The aim of this present narrative review is to provide a concise update of the ecological implications of the MDP, emphasizing its potential to promote food system sustainability and mitigate the negative consequences of global CC, in addition to its well-documented health-promoting beneficial effects in chronic disease prevention and treatment. In this review, we underline the importance of the MD as an eco-friendly dietary pattern with optimal human and environmental impacts; we discuss potential barriers to its widespread adoption; and we emphasize the urgent need to implement a dietary pattern with these qualitative characteristics for individual health and environmental protections, which are strongly interconnected.

2. Methods of Literature Search and Review Criteria

For the preparation of this present review, we applied the following search terms “Mediterranean diet”, “plant-based dietary patterns”, “sustainability”, “climate change”, “environmental footprints”, “greenhouse gas emissions”, “environmental impact”, “sustainable diets”, “sustainable food systems”, and “endocrine aspects”, in all possible combinations, in order to retrieve the available scientific literature data from the PubMed, Medline, and Google Scholar electronic databases from inception until June 2024. We included papers written in the English language that involved reviews, epidemiological reports, and observational and environmental studies, and additional references were retrieved from reviewing the references cited in the original articles.

3. The Definition of Sustainability and Sustainable Food Systems

The term “sustainability” has been defined by the World Commission on Environment and Development as “the development that meets the needs of the present, without compromising the ability of future generations to meet their own needs” [19]. Sustainable dietary patterns are characterized by the following three specific features: (1) low environmental impact of food production, (2) high food security, and (3) contribution to a healthier life. Sustainable diets respect and protect the biodiversity of ecosystems; they optimize natural and human resources; and they are easily accessible, economically affordable, and socioculturally acceptable [20,21]. In addition, a sustainable diet should be nutritionally balanced, healthy, and safe [22,23,24]. The principal target of a sustainable dietary pattern should be to keep GHG emissions within the planetary limits of sustainability and prevent serious health problems through a healthy dietary plan [25]. The Food and Agriculture Organization (FAO) and World Health Organization (WHO) clearly suggest that healthy and sustainable diets should provide adequate, safe, and nutrient-rich food for all [26]. It is also crucial to include the concept of territory in the definition of diet and food system sustainability, considering the strong interconnection between place and dietary behavior.

Due to the higher sustainability of plant-based foods in relation to foods of animal origin, it is suggested that a dietary plan with a higher proportion of these foods can have a drastic global environmental impact [27,28]. Omnivorous dietary patterns, reflecting the Western-type dietary habits prevalent in most countries, have a clearly negative environmental impact, mainly driven by the increased amount and frequency of animal food consumption [29,30]. More specifically, studies have shown that even a moderate consumption of animal food products (meat and dairy products) may be detrimental for environmental ecosystems and human health [2,31]. Based on these data, Pieper et al. concluded that a gradually reduced reliance of countries on animal food products could represent one of the most effective measures for the restriction of diet-related environmental impacts [32].

According to statistical figures from the WHO, over 800 million people in the global population are currently undernourished, while, at the same time, more than two billion are overweight/obese and display various micronutrient deficiencies [13]. Several health-promoting international organizations, such as “The United Nations (UN) Decade of Action on Nutrition (2016–2025)”, FAO, and WHO, are actively engaged in promoting sustainable food systems that contribute to healthy dietary patterns, with all of them being in line with the UN’s Sustainable Development Goals (SDGs) [33,34].

4. The Relationship of Sustainability with Climate Change

It has become more than evident that human activities can alter environmental aspects and transform the physical and biogeochemical environment all over the world [35]. Berry et al. have listed numerous activities with high environmental impact including urbanization, the reclamation of the land, deforestation, the intensification of agriculture, waste production, fresh water extraction, and the over-exploitation of fisheries [8]. All these activities have aggravating effects on vital environmental parameters such as climate variability, global warming and atmospheric composition, nitrogen cycling, water quality and quantity, land cover, sea levels, and biodiversity both on land and in the sea [8]. CC has been associated with biodiversity loss, food insecurity, unpredicted weather phenomena, and harmful health consequences [18].

The Mediterranean region is considered to be one of the most affected regions in terms of CC, presenting higher temperature levels in the summer, massive and devastating forest fires, reduced biodiversity, land degradation, and water scarcity. During the last decades, all these phenomena have been combined with a dramatic alteration of nutritional quality and reduced adherence to traditional Mediterranean diet patterns [36,37,38]. Of note, the Mediterranean region is a CC hotspot and one of the most water-scarce regions in the world. Due to the CC impact, the whole region presents serious problems with vegetation and the hydrologic cycle [39].

Under the pressure of the life-threatening effects of CC, the European Union (EU) has set the target to achieve the seventeen (17) SDGs of the UN Agenda for Sustainable Development by the year 2030 [40]. The aforementioned SDGs were adopted in 2015 by the 193 member states of the UN, and they are focused on optimizing food production, food distribution, and the preservation of natural resources, in order to mitigate the adverse CC consequences. Among the 17 goals, goal number 12, defined as “responsible production and consumption”, refers among other things to eating habits and to the production, processing, and consumption of food, in a process ensuring food system sustainability [40,41].

5. Defining the Characteristics of an Environment-Friendly Dietary Pattern

CC can affect diet through its effects on agricultural production. Factors such as high temperatures, the increased frequency of droughts, the salinization of agricultural land and aquifers, changes in the frequency and quantity of rainfall, the greater frequency of heat waves, and the rising levels of the sea have a deleterious effect on agricultural production [42]. According to the FAO’s report, “it will become more difficult and more expensive to grow, raise animals, managing forests and fish in the same places as before” [43]. For this reason, a shift of the contemporary unhealthy diet, being primarily based on animal-derived foods, towards a more plant-based dietary pattern, is expected to exert beneficial effects on the environment [31].

The EAT–Lancet Commission set as a major target to drastically reduce global GHG emissions by the year 2050. In this initiative, Willett et al. proposed an environment-friendly and healthy dietary pattern, mainly characterized by plant-based food products of high nutritional value, aiming to set a boundary of 5 Gigatons (Gt) of carbon dioxide equivalents (CO₂eq) per year related to food production, so as to reduce to about 50% total GHG emissions until 2050. This universal healthy reference diet consisted of fruits and vegetables, whole grains, legumes, nuts, and unsaturated oils and included low-to-moderate amounts of fish and poultry and nearly zero consumption of red meat, processed meat, refined carbohydrates, and starchy vegetables [25]. Using a measure to quantify adherence to the EAT–Lancet reference diet, namely the Planetary Health Diet Index (PHDI) in three large United States-based prospective cohorts of males and females with up to 34 years of follow-up, it was shown that a higher PHDI is associated with lower environment impact and a reduced risk of total and cause-specific mortality [44].

The term “dietary pattern” is used to denote the combination of foods and beverages (quantity, proportion, and variety) and the daily or weekly frequency of consuming each of them [16]. Several dietary patterns have been proposed to be effective in the prevention and treatment of different diseases. Robust scientific evidence supports the beneficial effects of dietary patterns based mostly on plant-derived foods (fruits and vegetables, vegetable oils, whole grains, legumes, nuts, and seeds) with a lower intake of animal products and ultra-processed foods [45,46]. The Dietary Guidelines released by the Scientific Advisory Committee of 2021 recommend that a plant-based dietary pattern promotes health and reduces environmental impact [47]. Plant-based diets minimize carbon and water footprints and simultaneously protect both human health and environmental integrity [48]. It has been shown that moving to diets that exclude animal products can significantly reduce global GHG emissions related to food production in Europe by nearly 50% [5]. Furthermore, plant-based dietary patterns have been associated with reduced freshwater and land use, lower biodiversity loss, protective effects on global food security, and improved water quality [45].

The “ideal” diet in terms of environmental impact is based on fruits and vegetables, whole-grain starchy foods, legumes, nuts and seeds, unsaturated fats, fish, and poultry and has a very limited consumption of red meat, processed meat products, and refined sugars. Unfortunately, current European dietary habits depart far from what is considered as ideal for the protection of global population health and environmental sustainability [5,25].

6. The Overall Health Benefits of the Mediterranean Diet

The positive effects of the MD on human health were originally described in the Seven Countries study by Dr. Keys and his colleagues in the early 1960s. This landmark study was the first to emphasize the protective effects of the MD against coronary heart disease (CHD) in people living in Mediterranean countries [49]. The MDP is widely recognized as a healthy and balanced dietary approach supported by strong scientific evidence, which is considered to be optimal for the maintenance of good physical and mental health, the promotion of longevity and healthy aging, and a reduction in the substantial health risks related to a wide variety of diseases including diabetes, obesity, CVD, and certain types of cancer, representing the leading mortality risk factors worldwide [13,18,50,51,52,53]. A population-based, prospective study with a large number of participants (22,043 adults in Greece), part of the European Prospective Investigation into Cancer and Nutrition (EPIC), has shown that increased adherence to the MD is strongly associated with a significant reduction in all-cause mortality [54]. The most consistent scientific evidence for the health benefits of the MD has been generated for cardiovascular risk factors and the incidence of CVD, but there is also a considerable body of evidence for the potential benefits of the MD for a wide range of other chronic diseases and health outcomes, including T2DM, metabolic syndrome (MS), obesity, cancer, cognitive decline, and CVD mortality [55].

The basic components of the traditional MD, as it was originally applied in the olive-growing regions of the Mediterranean basin around the decade of the 1960s, included the daily consumption of fruits and vegetables; the frequent intake of nuts, cereals and legumes; and the use of extra-virgin olive oil as the main form of added fat [18]. The original MD is primarily based on seasonal and locally grown foods. The numerous and well-documented protective effects of the MD have been established not only in countries of the Mediterranean area but also in other countries extending far beyond its geographic region [54,55,56]. Since the year 2010, UNESCO has acknowledged the MD as an intangible cultural heritage of humanity with a positive impact on human health and well-being [57,58].

The MD is not a strictly plant-based dietary pattern, but is actually partly omnivorous. The plant-based nature of this diet is supported by the following aspects: a high intake of olive oil as the main fat source; fruits, nuts, and seeds; freshly and naturally cooked vegetables; wholemeal cereals; herbs and spices; a moderate consumption of fish and poultry; a moderate consumption of red wine, mainly with meals; a low intake of full-fat dairy products; and a very low intake of red meat, processed meats, and sweets [16,59]. The MDP is not a unique dietary pattern, but it varies according to the specific country and local special considerations (with country-specific variations). The traditional MDP is closer to the traditional diet of Crete (Greece) in the middle of the 20th century (around the 1960s) [25,60].

7. Metabolic and Endocrine Aspects of Mediterranean Diet

The MD has been associated with lower incidence rates of new-onset diabetes and better glycemic control in patients with already established T2DM compared to control diets. Prospective observational cohort studies have shown that adherence to the MD is inversely associated with the risk of developing T2DM [61]. In a large cohort of 25,317 female participants from the Women’s Health Study, higher MD adherence was related to a 30% relative risk reduction for T2DM incidence during a 20-year follow-up period [62]. In a meta-analysis of eight prospective studies, the risk of T2DM was 13% lower among those following an MD, while a subsequent analysis of the ATTICA study including 3042 Greek participants, reported that medium–high adherence to the MD was associated with a 49–69% lower 10-year incidence rate of T2DM diagnosis compared to low adherence [63]. These data were further corroborated in the landmark PREDIMED trial, in which an MD enriched with extra-virgin olive oil or nuts resulted in a 30% T2DM risk reduction compared with the control group [64]. In the field of randomized controlled clinical trials (RCTs), a meta-analysis of five RCTs has shown that the MD may provide better glycemic control in patients with T2DM and prediabetes, compared with control diets, mainly represented by low-fat diets [65]. Apart from improvements in glucose metabolism (fasting and postprandial glucose and insulin levels and glycated hemoglobin), the MD can also beneficially affect other cardiovascular risk factors, such as the lipid profile and blood pressure, in patients with T2DM [66]. It can also alleviate the burden of diabetes-related microvascular (in addition to macrovascular) complications, such as diabetic retinopathy and diabetic chronic kidney disease, by preventing/delaying their onset and improving their prognosis [67,68]. Furthermore, the MD has been proposed as the gold standard nutritional intervention for patients with T2DM and concomitant metabolic dysfunction-associated steatotic liver disease (MASLD), which is a common comorbidity of T2DM with an increasing prevalence worldwide [69]. The MD has shown the potential to improve both biochemical and histological features of diabetes-related steatotic liver disease and exert significant hepatoprotective actions [70].

With regard to MS, a meta-analysis of 12 observational studies with a total of 33,847 individuals and 6342 cases of MS, showed a 19% lower risk of MS associated with greater adherence to the MD [71]. In another meta-analysis of two RCTs, there was a 49% greater likelihood of MS remission in those allocated to an MD over a follow-up of 2–5 years, compared with those following control diets [65]. In terms of the potential for weight loss, there is strongly suggestive evidence derived from observational and intervention studies that the MD does not promote weight gain despite its relatively high fat content, but, on the contrary, it may be associated with moderate weight loss and a selective reduction in abdominal adiposity, especially in the setting of energy restriction and combined with increased physical activity [51,72]. It has been suggested that the MD can reduce central adiposity and visceral fat accumulation independently of weight loss. Cross-sectional studies have shown that adherence to the MD is inversely associated with the markers of abdominal adiposity [73,74]. Interventional clinical trials have also shown that visceral adipose tissue can be significantly reduced with the MD [75,76]. These beneficial effects are possibly related to the high content of polyunsaturated (PUFA) and monounsaturated (MUFA) fatty acids, and the low intake of saturated fatty acids (SFAs), which are the predominant lipid component of visceral fat mass.

The plant-based components of the MD (fruits, vegetables, whole grains, and nuts) are rich in polyphenols, namely bioactive compounds with important antioxidant and anti-inflammatory properties that have been shown to reduce insulin resistance and ameliorate multiple cardiometabolic risk factors [77,78]. According to the “fluid aspect concept” of the MD, the olive oil and the low-to-moderate alcohol intake (especially red wine), being the principal fluid components of the MD, can further contribute to the benefits of the MD via their rich polyphenol content [79]. Olive oil contains at least 30 phenolic compounds, while the major red wine polyphenols include flavonols, flavanols, anthocyanin, and stilbenes (resveratrol). Overall, the major mechanisms underlying the well-documented beneficial cardiometabolic effects of the MD and its important role in the prevention and management of T2DM, obesity, MS, and CVD comprise the following: a reduction in oxidative stress and inflammation; the improvement of insulin sensitivity and glucose metabolism; the modification of plasma lipoprotein composition and function; the improvement of the fasting lipid profile; the attenuation of postprandial lipemia; the improvement of endothelial function and a reduction in proatherogenic gene expression; the modulation of gut microbiota in the direction of a more balanced and biodiverse gut microbiome profile; and antithrombotic and immunomodulatory properties [79,80]. Extra-virgin olive oil, in particular, representing the principal functional component of the MD, being characterized by a high total polyphenol content and the balanced composition of MUFAs and PUFAs, has been suggested to be involved in the upstream and downstream intracellular networks of insulin receptor signaling, thus playing an important role in regulating insulin actions at the cellular level [78]. Although not all the phenolic compounds of extra-virgin olive oil are systematically absorbed, reaching the desired bioavailable/bioactive concentrations within insulin-sensitive tissues, oleacein, through its relatively high lipophilicity accounting for improved survival with respect to gastric acids and enhanced intestinal absorption into the systemic circulation, may be capable of inducing insulin-sensitizing actions, which might be clinically relevant for diabetes prevention in people adhering to the MD [81].

Beyond its effects on cardiometabolic outcomes, the MD has been further proposed as a highly recommended dietary intervention for the prevention and management of a variety of endocrine diseases, including thyroid disorders, gonadal disorders (i.e., polycystic ovary syndrome; PCOS), and neuroendocrine tumors, highlighting the need for interdisciplinary collaboration between endocrinologists and nutritionists for optimizing the outcomes of these patients [82]. A growing body of evidence suggests that the MD has the potential to reduce the risk of nodular thyroid disease, autoimmune thyroiditis, and thyroid cancer; improve male and female reproductive health; and optimize the therapeutic management of patients with neuroendocrine tumors [82]. Most of these effects can be largely explained by the anti-inflammatory and antioxidant properties of the MD related to its high content in phytochemicals [82].

8. Mediterranean Diet and Sustainability

Different dietary patterns may have distinct environmental impacts [83,84]. According to an interdisciplinary committee addressing climate degradation and proposals for a healthy diet and a sustainable food production process, among all the dietary patterns studied, the best pattern was that of the MD, and more specifically a diet similar to the Cretan diet as it was practiced in the middle of the 20th century [85,86]. This dietary pattern is characterized by a low intake of red meat and a high consumption of plant foods and olive oil [87].

The MD may serve as an outstanding model and an exemplary case of a sustainable nutritional system. Apart from its significant beneficial effects on human health, the economy, and sociocultural aspects [8,88], the MDP is considered to be a sustainable diet, which can play an essential role in the environment and CC. The MDP has similar characteristics as other sustainable diets such as vegan diets and the DASH diet (Dietary Approach to Stop Hypertension), characterized by a low consumption of animal products and a positive contribution to biodiversity and local cultural heritage [89].

Table 1. A summary of the major studies investigating the environmental impact of the Mediterranean dietary pattern.

Author (Year)	Aim of the Study	Study Design and Methods	Study Population	Major Findings
Filippin D et al. (2023) [2]	To compare two plant-based, isocaloric diets (vegan diet vs. MD) in terms of their environmental impact.	Life cycle assessments were used to investigate the total environmental impact of two diets according to relevant Italian dietary recommendations, with calculations based on a theoretical 2000 kcal/d diet for one week.	NA	A vegan diet showed 44% ↓ total environmental impact vs. the MD, despite the low animal product content of the MD; even a minimal-to-moderate content of animal products has a detrimental impact on the environment, and their reduction can be ecologically beneficial.
Bordoni A et al. (2023) [1]	To evaluate the WF of the recommended Italian diet, which is a version of the MD.	The WF of various food products was calculated by averaging the data reported in a published dataset in each food category, taking into account Italian eating habits.	Italian population	The Italian version of the MD showed a ↓ WF; it is necessary to inform consumers, farmers, and producers about water-saving choices.
Tucci M et al. (2022) [10]	To compare the CF and WF of an Italian Mediterranean version of the EAT–Lancet reference diet (EAT-IT) with a diet based on Italian dietary guidelines.	Data related to the CF (accounting for GHGs) and WF (accounting for water consumption) were retrieved from a multi-level dataset of food commodities, assigning footprint values to food items; weekly dietary patterns were developed (2500 kcal/d), considering food categories, portions, and frequencies of intake.	Italian population	Compared to the diet based on the Italian guidelines, the EAT-IT pattern had ↓ CF but similar WF; protein-rich foods (meat and dairy) were the main contributors to the CF and WF in both patterns; the EAT-IT pattern is sustainable in terms of CF, but individual choices can largely affect environmental outcomes.
Giosuè A et al. (2022) [5]	To propose an ideal dietary pattern for CVD prevention.	Systematic review of meta-analyses of prospective studies.	European population	The proposed diet had 48.6% ↓ CF compared to the current European diet.
Castaldi S et al. (2022) [7]	To compare the environmental impact of the MD between the MED and non-MED countries in the EU.	A compilation of 3449 CF values of food commodities, based on a standardized methodology, was used to estimate the GHG emissions related to food consumption, using 2017 as a reference year.	Seven MED countries and twenty-one non-MED countries in the EU	GHG emissions were comparable between the MED and non-MED countries, mainly driven by meat over-consumption in the Mediterranean countries.
Rosi A et al. (2020) [90]	To investigate the dietary environmental impact of Italian children, according to their adherence to the MD.	Observational study with calculations of carbon and ecological footprints.	N = 172 primary school children living in Parma (8–10 years old)	Carbon and ecological footprints were higher in winter than in summer, and the main dietary contributors were red and processed meat; there was a weak positive correlation between MD adherence and environmental footprints due to higher energy intake; the overall food intake is more important than the consumption of specific food groups in terms of environmental implications.
Fresán U et al. (2018) [91]	To evaluate the impact of MD adherence on resource use (land, water, and energy) and GHG emissions in a Mediterranean Spanish cohort.	Life cycle assessments were used to assess the environmental footprint of food item production and processing.	N = 20,363 Spanish university graduates, SUN cohort (1999–2015)	Higher MD adherence was associated with ↓ land use, ↓ water and energy consumption, and ↓ GHG emissions.
Sáez-Almendros S et al. (2013) [92]	To compare the current SDP with the MDP and WDP in terms of environmental footprints.	Food balance sheets and household consumption surveys were used for the dietary composition; life cycle assessments were used to assess environmental footprints.	Spanish population	Increasing adherence to the MDP was associated with ↓ GHG emissions (72%), ↓ land use (58%), ↓ energy consumption (52%), and ↓ water consumption (33%); adherence to the WDP increased all these indices (12–72%).
Álvarez-Álvarez L et al. (2024) [84]	To evaluate the impact of a 12-month hypocaloric MD intervention on environmental sustainability in older adults with metabolic syndrome.	Longitudinal analysis of the PREDIMED-Plus trial cohort, which was a multicenter, randomized, 8-year intervention trial on the MD; the food intake was estimated using validated food frequency questionnaires; and the environmental outcomes were assessed with the EAT–Lancet Commission tables.	N = 5800 older Spanish adults with metabolic syndrome (PREDIMED-Plus trial cohort)	High adherence to an energy-restricted MD for one year was associated with lower GHG emissions (−361 g/CO2 equivalents), land use (−2.2 m2), energy use (−842.7 kJ), acidification (−11.5 g SO2 equivalents), and eutrophication (−4.7 g PO4 equivalents); meat products had the greatest environmental impact.
Galli A et al. (2017) [93]	To examine the ecological footprint of food production and consumption in 15 Mediterranean countries.	The ecological footprints of food production and consumption were expressed in global hectares (gha)/year per capita.	Fifteen Mediterranean countries (Cyprus, France, Greece, Italy, Malta, Portugal, Slovenia, Spain, Albania, Croatia, Israel, Turkey, Egypt, Morocco, and Tunisia)	The average ecological footprint in the 15 Mediterranean countries was 0.87 for food production and ~0.86 for food consumption. Portugal, Malta, and Greece were found to have the highest food ecological footprint per capita (1.50, 1.25, and 1.22 gha/year), while Slovenia, Egypt, and Israel had the lowest (0.63, 0.64, and 0.79 gha/year, respectively).
Germani A et al. (2014) [89]	To compare the environmental impact of the current food consumption pattern of the Italian population and the MDP.	The environmental impact was calculated on the basis of three indices (CF, WF, and EF).	Italian population	The MDP had a lower CF, WF, and EF than the current Italian dietary pattern; the MDP had a CF of 17.04 kg CO2 equivalents/week per capita, a WF of 13,781 L/week per capita, and an EF of 129 m2/week per capita.
Naja F et al. (2018) [94]	To evaluate and compare the environmental footprints of food consumption patterns among Lebanese adults.	Based on food intake assessment through a food frequency questionnaire, dietary patterns were identified (Western, Lebanese Mediterranean, and high-protein); life cycle analyses were reviewed to estimate the water use, energy use, and GHG emissions.	N = 337 Lebanese adults	The Western and high-protein dietary patterns had high environmental footprints, whereas the Lebanese MDP had lower water use and GHG emissions; the Lebanese MD had a water use of 602.06 L/day, energy use of 10.82 MJ/day, and GHG emissions of 0.90 kg CO2 equivalents/day per capita.
Vanham D et al. (2021) [95]	To compare the water resources related to food consumption in three different dietary patterns (current diet, MD, and EAT–Lancet diet) in nine Mediterranean countries	The WF was calculated.	Nine major Mediterranean countries (Spain, France, Italy, Greece, Turkey, Egypt, Tunisia, Algeria, and Morocco)	The MD requires more water resources than the EAT–Lancet diet; the total WF of the MD (L/day per capita) ranges widely across Mediterranean countries (2966 in Spain, 2818 in France, 2874 in Greece, 2571 in Italy, 2819 in Turkey, 2819 in Egypt, 4516 in Morocco, 3946 in Algeria, and 4650 in Tunisia); the average WF of the MD for the nine Mediterranean countries was 3.33 L/day per capita.
Belgacem W et al. (2021) [96]	To compare the pressures of three different dietary patterns (European, Western, and MDP) on biodiversity through effects on land use, water use, GHG emissions, and eutrophication indices.	The environmental impacts of each dietary pattern were calculated based on a compositional analysis (the dietary scenarios were constructed based on food balance sheets); the environmental footprints of each food product were retrieved from life cycle assessment studies.	NA	The MDP preserves biodiversity; the shift from the European diet to the MDP would lead to 10 m2/capita/day land savings, 240 L/capita/day water savings, a 3 kg CO2/capita/day reduction in GHG emissions, and a 20 g PO4 equivalents/capita/day reduction in eutrophication potential; a shift from the Western diet to the MDP would lead to 18 m2/capita/day land savings, 100 L/capita/day water savings, a 4 kg CO2/capita/day reduction in GHG emissions, and a 16 g PO4 equivalents/capita/day reduction in eutrophication potential.
Mattas K et al. (2023) [97]	To compare biodiversity in terms of food plant species, subspecies, varieties, and races between the MDP and Western-type dietary patterns.	The data were collected from plant databases with a two-stage approach; 12 countries from North Africa and Europe were classified into two groups (MDP vs. Western-type diets) according to their traditionally most prevalent dietary pattern.	Six MED countries (Greece, Italy, Malta, Morocco, Algeria, and Lebanon) vs. six non-MED European countries (Belgium, Switzerland, Germany, Austria, Denmark, and Sweden)	The agricultural biodiversity in food plant varieties, species, and subspecies was higher in the MDP compared to Western-type diets; this greater diversity was associated with better crop utilization but not food plant availability in the MED countries; Italy had the most diverse cuisine in both native and cultivated food plants, while Denmark showed the lowest food plant diversity.
García S et al. (2023) [98]	To study the association between the adherence to an energy-restricted MD and dietary CO2 emissions in an older adult population.	A cross-sectional study, where the food intake and MD adherence were assessed with validated food frequency questionnaires and a 17-item MD questionnaire; the CO2 emissions of each participant diet per day were calculated using a European database; the participants were distributed into quartiles, according to their estimated CO2 emissions (kg/day).	N = 6646 older Spanish adults with metabolic syndrome	Higher adherence to the MD was inversely associated with dietary CO2 emissions; MD adherence may be used as a pollution level index.
Tepper S et al. (2022) [99]	To assess the environmental footprints (land use, water use, and GHG emissions) related to the MD, the EAT–Lancet diet, and the Sustainable Healthy Diet (SHED) previously validated in the Israeli population.	Dietary assessment was performed with a 116-item food frequency questionnaire validated for the Israeli population; adherence to the MD was calculated using a 9-point score; adherence to the EAT–Lancet diet was assessed through the consumption of 14 food components; and the environmental footprints per unit of food product were calculated for each dietary pattern.	N = 525 Israeli participants	The highest tertile of adherence to the MD, EAT–Lancet diet, and SHED was associated with the lowest GHG emissions and land use but with higher water use; meat consumption was the major contributor to land us, dairy products were the major contributor to GHG emissions, and fruits contributed the most to water use.

CF: carbon footprint; CVD: cardiovascular disease; EF: ecological footprint; EU: European Union; GHG: greenhouse gas; MD: Mediterranean diet; MED: Mediterranean; MDP: Mediterranean dietary pattern; NA: non-applicable; SDP: Spanish dietary pattern; WDP: Western dietary pattern; and WF: water footprint.

summarizes the major studies investigating the environmental impact of the MDP.

In Spain, the MDP is considered as a traditional dietary model but also a healthy and environment-friendly dietary pattern. A large number of Spanish studies suggest that the MDP may contribute to the high sustainability of food production and consumption systems, in parallel with a positive impact on public health [92]. According to the study by Sáez-Almendros et al., the adherence of the Spanish population to the MDP is able to decrease the environmental footprint. The increased adherence to the MDP in Spain could lead to a reduction in GHG emissions by 72%, land use by 58%, energy consumption by 52%, and water consumption by 33%, as opposed to a Western dietary pattern, which would increase all these environmental factors by 12–72% [92]. According to another observational study conducted in Spain (the SUN cohort study), greater adherence to the MDP was associated with lower land use, lower energy and resource consumption, and reduced GHG emissions [91]. Another relevant longitudinal study was conducted in Spain, with the data collected at baseline and after one year of MD intervention in the participants of the PREDIMED-Plus trial cohort, which was a multicenter, randomized, controlled 8-year intervention trial on the effects of the MD in older subjects with metabolic syndrome [52,65]. According to this study, high adherence to an energy-restricted MDP was strongly associated with a lower environmental impact in five specific environmental domains: GHG emissions, land use, energy use, acidification, and eutrophication. The results of the latter study have shown that after one year of dietary intervention with the MDP, these five indicators were all decreased. More specifically, the MD intervention was associated with lower GHG emissions (−361 g/CO₂ equivalents), land use (−2.2 m²), energy use (−842.7 kJ), acidification (−11.5 g SO₂ equivalents), and eutrophication (−4.7 g PO₄ equivalents). It was also shown that meat products had the greatest environmental impact among all the food items examined [84]. Considering that meat products had the highest environmental impact across all five dimensions, the MDP with a lower consumption of animal foods may reduce even more the negative diet-related environmental impact [100,101,102]. In a subsequent publication of the same group, it was shown that the one-year MD intervention in the same population was associated with greater reductions in acidification (−13.3 compared to −9.9 g of SO₂ equivalent), eutrophication (−5.4 compared to −4.0 g of phosphate equivalent), and land use (−2.7 compared to −1.8 m²), compared to the control group who received only advice about the MD without active weight loss promotion [103]. In the latter study, it was also shown that adherence to the diet and the caloric reduction could partially mediate the observed beneficial environmental effects [103].

In alignment with the above data from the Spanish studies, the beneficial environmental impacts of the MDP have been consistently demonstrated in other populations as well. A population-based study in Israel, comparing the environmental footprints of three healthy dietary patterns (the MD, EAT–Lancet reference diet, and the Healthy Sustainable Diet, which was previously validated in the Israeli population), has shown that higher adherence to all these dietary patterns is associated with lower land use and GHG emissions but with higher water use [99]. This study identified meat consumption as the major contributor to land use, dairy products as the major contributor to GHG emissions, and fruit consumption as the major contributor to water use [99]. An additional study conducted by Metin et al. in a total of 1797 Turkish participants aimed to evaluate the relationship between adherence to the MDP, healthy and sustainable eating behaviors, and CC awareness in the Turkish population [104]. The study reported a statistically significant positive correlation between three specific scores: the MDP Adherence Scale (MEDAS), the Sustainable and Healthy Eating Behaviors Scale, and the Climate Change Awareness Scale. The study found a significant relationship between CC awareness, sustainable and healthy eating behaviors, and adherence to the MDP [104].

Beyond the above-mentioned population-based cross-sectional studies, the sustainability of the MD has also been addressed in comprehensive reviews. A systematic review of 32 studies assessing several sustainability indices of the MD (related to its environmental impact, nutritional quality, and economic and sociocultural aspects) concluded that there is actually no uniformity in evaluating the sustainability of this dietary pattern, since there are several different aspects to be considered, which can be examined either in isolation or in combination [15]. Focusing on the 25 studies that aimed to quantify the environmental dimensions of the MD in this systematic review, it was shown that the MD has a lower overall environmental impact compared to Western diets, as captured by a carbon footprint ranging between 0.9 and 6.88 kg CO₂/day per capita, a water footprint ranging between 600 and 5280 m³/day per capita, and an ecological footprint ranging between 2.8 and 53.42 m²/day per capita [15]. It should be noted that the studies assessing the environmental aspects of the MD have usually applied more than one index to address the environmental sustainability of this diet, including carbon footprint/GHG emissions, water footprint, ecological footprint (land use), energy use, freshwater and marine eutrophication, plant/animal protein intake ratio, particulate matter/respiratory organics, and organic and local food consumption [90,91,92,93,94,95,96,105,106]. The data of this review reveal the need for a harmonized compilation of the indices that can be applied to the MD in order to provide a complete and comprehensive assessment of its several sustainability dimensions.

Among all the indices that have been used to assess the environmental footprint of the MD, the most commonly measured outcome is carbon footprint/GHG emissions, which is related to global warming potential. A representative study investigating the association between dietary CO₂ emissions and the adherence to an energy-restricted MD in an older Spanish population with metabolic syndrome, has shown that subjects with greater adherence to the hypocaloric MD induce lower levels of dietary CO₂ emissions and therefore pollute the environment to a lesser extent [98]. In this study, the high consumption of fruits, vegetables, legumes, nuts, and whole cereals and the preferential selection of white vs. red meat were inversely associated with dietary CO₂ emissions [98].

The concept of biodiversity preservation is a fundamental component of MD sustainability. Biodiversity is a key requirement for dietary diversity and food security. Although biodiversity is a difficult-to-quantify environmental outcome and does not belong to the classical sustainability indicators measured in most studies, its interlinkage with the MD has been widely discussed in the literature [96,97]. In a study comparing the environmental pressures of three distinct dietary patterns (European, Western, and the MDP) on biodiversity through their effects on land use, water use, GHG emissions, and eutrophication indices, it was suggested that shifting from the European to the MDP would lead to 10 m²/capita/day of land savings, 240 L/capita/day of water savings, a 3 kg CO₂/capita/day reduction in GHG emissions, and a 20 g PO₄ equivalents/capita/day reduction in eutrophication potential. In the same direction, a shift from the Western to the MDP would lead to 18 m²/capita/day of land savings, 100 L/capita/day of water savings, a 4 kg CO₂/capita/day reduction in GHG emissions, and a 16 g PO₄ equivalents/capita/day reduction in eutrophication potential [96]. In the same field of biodiversity, it has been further suggested that the Mediterranean countries that traditionally adopt the MDP (such as Greece, Italy, Malta, Morocco, Algeria, and Lebanon) display a greater biodiversity in cultivated food plant species (agricultural biodiversity) compared to countries with the prevalent Western-type dietary patterns, substantiating the potential of the MDP to protect biodiversity and support nutrition security and sustainable development [97].

Figure 1 illustrates in a graphical way the sustainability features of the MD, which make it an “ideal” dietary model for the protection of planetary health.

9. Mediterranean Dietary Polymorphism and Environmental Implications

Mediterranean diets are far from homogeneous. There are several country-specific MD variations, which are largely determined by an interplay of local, religious, cultural, geographical, and ecological factors. It is noteworthy that, even within the same country, significant dietary differences can be observed. In Italy, for example, the consumption of cereals, fruit, and vegetables is higher in the southern than in the northern part of the country [107]. There are currently considerable discrepancies in the prevalent dietary patterns between the northern Mediterranean countries (Greece, Italy, Spain, France, and Portugal), Balkan countries (Bosnia-Herzegovina, Croatia, Serbia, and Slovenia) and southeastern Mediterranean countries (SEMCs) (Algeria, Egypt, Lebanon, Morocco, Syria, Tunisia, and Turkey). The diets in the SEMCs are mainly vegetarian, with cereals constituting the basic ingredient and pulses being the main protein source. In northern Mediterranean countries, on the other hand, foods of animal origin are more prominent, although in limited consumption. The dietary pattern in the Balkan countries is placed somewhere between the other two patterns, so that they are richer in animal products than the SEMCs, but they contain more cereals and pulses than the northern Mediterranean countries [108]. A common observation is that the contribution of plant-based products to total dietary energy intake has decreased in most Mediterranean countries in the last years, especially in the period between 1990 and 2009 [108]. In fact, there have been only slight increases in the cases of Algeria (+0.27%), Italy (+0.36%), Libya (+1.02), Cyprus (+1.27%), and France (+4.48%), while decreases have been observed in Spain (−0.19%), Albania (−12.04%), Bosnia (−6.17%), Portugal (−5.80%), Croatia (−3.05%), Lebanon (−3.20%), Israel (−2.41%), Greece (−2.19%), Morocco (−1.65%), Tunisia (−1.83%), and Malta (−1.13%). In parallel with this decrease in plant-based food consumption, the average consumption of animal-derived protein over the same time period has increased from +1.7% in Italy to +69.2% in Egypt and +75% in Albania. The average animal protein intake has also increased significantly in Lebanon (+45.8%), Tunisia (+36.8%), Portugal (+32.7%), Syria (+31.6%), Morocco (+33.3%), Israel (+26.3%), and Algeria (+21.1%). Between 1960 and 2000, there has been a significant increase in average global meat consumption. More specifically, in the Near East and North Africa, meat consumption has increased from 11.9 to 35.0 kg/capita/year, while milk consumption has increased from 21.2 to 72.3 kg/capita/year [108].

Considering the differences in animal and plant protein intake between northern and southeastern Mediterranean countries and taking into account the detrimental impact of meat consumption on environmental outcomes, it can be assumed that the different dietary patterns across the Mediterranean region might further translate into distinct environmental impacts. However, the environmental repercussions of the dietary diversity within the Mediterranean region have not yet been adequately addressed in the literature.

10. Identifying Barriers to the Widespread Implementation of the Mediterranean Diet

Adherence to healthy and sustainable dietary patterns such as the MD is not easy at all. The adoption and successful implementation of this diet should be considered as a real challenge for people in the developed world but also in the developing countries, where people mostly suffer from poverty and malnutrition [13,109,110].

The question of whether worldwide MD applicability is feasible still remains, mainly due to barriers related to different cultures and traditions. Studies have shown that adherence to the MD might be difficult for populations living far from the Mediterranean basin [111]. The main factors that have been recognized to influence adherence to the MDP are financial, sociocultural, cognitive, sensory, motivational, demographic, and also related to the accessibility and availability of MD food products. A review by Gibbs and Cappuccio, in 2022, outlined the most prominent perceived and objective barriers preventing people from transitioning to plant-based diets. According to this review, the main barriers to the widespread adoption of plant-based dietary patterns, including the MD, comprised meat appreciation, health concerns related to potential nutrient deficiencies, convenience, taste factors, and cost issues [45]. Another relevant study explored the public understanding of the link between food, environment, and CC and, more specifically, attitudes towards reducing meat consumption. The study revealed that participants were not aware of the association between meat consumption and CC and also of the magnitude of personal meat consumption’s effect in the global context of CC. The participants were also unwilling to reduce their personal meat consumption [112].

11. Concluding Remarks and Critical Perspectives

Our eating habits and individual food choices can influence the connection between food production systems and critical environmental dimensions, such as GHG emissions and global earth warming. Animal-based products contribute significantly to the increased environmental footprints of diets. Dietary patterns such as the Western dietary pattern, with a high consumption of animal food products, can lead to environmental degradation and relatively high GHG emissions. On the contrary, it has been shown that a dietary shift to the MDP can significantly reduce major environmental impacts, such as GHG emissions, land use, and energy and water consumption.

The adoption of healthy dietary patterns is crucial to achieve sustainable development as a means to counteract food insecurity and malnutrition. There is an urgent need for public health strategies to achieve healthy sustainable diets, improving energy balance and dietary options towards predominantly plant-based diets aligned with healthy eating guidelines. In parallel with the adoption of sustainable diets such as the MDP, scientists all over the world should take different factors into consideration, including local climate and culture settings, water availability, the diversity of agricultural production systems, and the physical properties of soil and land. It is suggested that future studies should adopt a more holistic approach and propose the concept of a “Planeterranean” diet, which could be applicable worldwide [113].

Overall, the available scientific evidence clearly suggests that a diet high in plant-based whole foods makes up the dietary pattern that is most associated with reduced morbidity and mortality, increased longevity, and improved quality of life. Reducing meat consumption is also fundamental from an environmental perspective, in order to optimize diet sustainability. The MDP, as a typical example of a plant-based dietary pattern, is widely recognized as a sustainable dietary model that promotes optimal individual and planetary health. The MDP gained enormous attention mainly due to its proven effects on different aspects of health, but also due to its taste that facilitated a widespread popularity even among non-Mediterranean populations. It is important, however, to emphasize that the MDP is not just a list of ingredients, foods, and recommendations. It has many underestimated aspects of dietary behavior such as the consumption of spices and herbs, cooking methods, food quality, lifestyle, and sleeping patterns, as well as connection with the territory, which should also be implemented in order to take full advantage of its beneficial environmental impact [112,113].

Despite strong scientific evidence substantiating the beneficial effects of the MDP on the environment, there are still several barriers to its widespread implementation, especially in countries located beyond the Mediterranean basin, which have not yet been adequately addressed. Country-specific variations, adapted to the local culture and culinary tradition of each country, need to be designed and validated in terms of their environmental impact. It should be clearly stated that any proposed healthy sustainable diet should consider local biodiversity and cultural and social differences among different countries. It is also important to emphasize that food system sustainability should value local solutions and respect local characteristics. Furthermore, although a number of studies have used specific indicators of environmental sustainability and provide compelling evidence that they are all improved with the MD, there is no study assessing a complete set of environmental dimensions in the comprehensive and systematic way that the EAT–Lancet Commission project performed with regard to the proposed healthy reference diet. Last but not least, whether reducing further the animal product intake in the setting of a modified MD version similar to the vegan diet would elicit additional ecological benefits remains to be investigated with future studies. In this context, nutrient adequacy aspects need to be meticulously considered.