1. Introduction
People and planetary health are clearly interconnected. Human health is directly affected by the quantity and the quality of foods that we consume [
1,
2,
3]. Climate and environmental changes have impacted food production by decreasing agricultural yields and increasing food insecurity and water scarcity in some regions of the world [
4,
5]. It should be noted, however, that one of the major forces of these changes in the ecosystems is the food chain. Around 30% of the total anthropogenic greenhouse gas (GHG) emissions and 70% of fresh water usage are from the food sector [
6]. The food sector is also one of the leading causes of land use change and loss of biodiversity [
7]. Moving to a more sustainable agriculture technology and reducing food losses have been proposed to address this issue. However, these measures are not enough. A change in dietary habits at the population level is necessary [
8,
9,
10,
11,
12].
Comparing different strategies aimed at modifying global dietary patterns to improve human and planetary health, such as reducing the consumption of animal-sourced products and lowering caloric intake, the former has been suggested as the most effective strategy [
13]. Well-planned plant-based diets have been recognized as nutritionally adequate, and appropriate for human growth and development. Such diets are suitable not only in the prevention but also in the treatment of many chronic diseases [
14,
15,
16]. Diets rich in plant-based products and low in animal-sourced foods are associated with lower risks for diseases such as type 2 diabetes, obesity, cancer, and coronary heart disease, as well as a greater life-expectancy [
17,
18,
19]. At the same time, plant-based diets are more environmentally friendly. They are typically associated with considerably less GHG emissions compared with that of meat-based diets [
20,
21]. This is primarily because the production of animal-derived foods, especially beef, generate a bigger carbon footprint than the production of plant foods [
22]. In fact, among those who consume animal-based products, these foods are the major contributors to the carbon footprint of their diets [
23].
The adoption of plant-based diets could be difficult for some people. Various barriers exist, such as the enjoyment of meat or the difficulty of changing established cultural eating habits [
24,
25,
26]. The options available to people in making the shift must be acceptable on a personal, nutritional, financial, and environmental basis. The World Watch Institute has proposed meat analogs as viable lower carbon footprint alternatives to processed meat products [
27]. Meat analogs are processed convenience foods, rich in protein, that are prepared to resemble meat in texture and appearance [
28]. In addition, they are often flavored to smell and taste like chicken, beef, turkey, or fish. Over the past decade, there has been an increased use of a number of meat analogs that are marketed and sold as protein-rich substitutes for meat [
28,
29]. More than one third of Americans have reported purchasing meat analogs at some time [
30]. In addition to their popularity among vegetarians, the meat analogs are also consumed by non-vegetarians who wish to cut back on meat, and who choose them as a healthy alternative or as part of a more environmentally friendly diet [
31].
A few publications have focused on the assessment of the carbon footprint of meat analogs [
32,
33,
34,
35,
36]. All concluded that meat analogs are a more sustainable alternative to meat and processed meat products. In addition, many meat analogs qualify as complete proteins and also contain substantial levels of dietary fiber, natural antioxidants and phytochemicals, while possessing a low saturated fatty acid content and no cholesterol [
16,
37]. Meat analogs are typically formulated from wheat or soy protein, but may also contain mycoprotein, nuts, legumes and/or vegetables [
29]. Some may also contain animal-sourced ingredients such as egg or milk. People may choose to avoid specific types of meat analogs for different reasons, such as food allergies/intolerances (i.e., celiac disease, soy and nut allergies) or to follow a specific type of dietary pattern (e.g., gluten-free or vegan diets). Meat analogs are mainly consumed by health-conscious individuals, who are often aware of the sustainability of their diet [
31]. Variation in sustainability and nutritional composition among these products could be a factor in consumer choices. It is known that different types of animal-sourced protein foods (e.g., chicken, pork, and beef) differ in both their environmental impact and nutritional composition [
22,
37]. According to the U.S. Department of Agriculture, beef consumption peaked in the mid-1970s, while chicken consumption has doubled since that time [
38]. This change in eating habits is due in large part to the increased awareness of the effects of red meat consumption upon one’s health [
39]. There is a lack of published research assessing the environmental impact and nutritional value of meat analogs derived from different protein sources. As was the case for animal-based protein, this knowledge could be used for a more conscious decision when opting for specific meat analogs.
Therefore, we compared the GHG emissions derived from the production of different types of meat analogs according to their main protein source, and their nutritional composition. Additionally, we also compared totally plant-based meat analogs with those containing egg.
4. Discussion
The choice to consume or avoid specific types of meat analogs is driven largely by personal preference or health reasons. Consumers who avoid wheat-based products may do so because of medical conditions (e.g., celiac disease, non-celiac gluten sensitivity and wheat allergy) or because they are following a special type of diet (e.g., gluten- and grain-free). Soy and nut allergies could be reasons for avoiding soy- and nut-based meat analogs, respectively. Additionally, genetically modified soybean is a common ingredient in commercial products; people trying to follow a non-GMO (genetically modified organism) diet could prefer the avoidance of soy-based products. Independently of egg allergy, there is an increasing number of people seeking total plant-based products. Meat analogs are mainly consumed by people searching for sustainable and nutritious foods. Therefore, consumers may compare sustainability and nutrition differences when selecting specific meat analogs. Consumer information regarding these attributes validates the need for additional research.
In the current investigation we assessed the carbon footprint and nutrient composition of more than 50 meat analog products according to the main source of protein and the presence of eggs. An ever-increasing number of protein sources are being used to produced meat analogs. Vegetable proteins are currently the main source of material for meat analogs, especially gluten of wheat and soybean protein [
29]. Others, such as protein derived from pulses, nuts or vegetables, are also utilized. The current analysis assesses specifically plant-based meat analogs. The majority of the meat analogs we analyzed (49 out of 56) were either wheat-based products and/or soy-based products.
Previously, the assessment of carbon footprint data for meat analogs focused on the description of the GHG emissions of the analogs [
32,
34]. Other reports compared the emissions of meat analogs with animal-based products [
34,
36]. Few studies showed differences between various types of meat analogs. We recently published a comparison of the emissions of meat analogs, but differences were reported according to their commercial preparation (i.e., burger, sausage) or format (i.e., canned, frozen) [
35]. In another study, Smetana et al. reported the GHG emissions of meat analogs by the main source of protein [
33], with results similar to those of our study. For the 32 wheat-based products we assessed in the current study, the GHG emissions ranged from 0.12 to 0.39 kg CO
2e/100 g product compared to 0.36–0.40 kg CO
2e/100 g reported by Smetana et al. [
33]. For the seven soy-based products we assessed, GHG emissions ranged from 0.13 to 0.36 kg CO
2e/100 g, a level comparable to that reported elsewhere for soy-based products (0.27–0.28 kg CO
2e/100 g) [
33]. We note that in the study by Smetana et al., no statistical comparisons were performed and the research group only assessed one product of each type, while in our study 56 different products were analyzed. Our results showed no major differences in GHG emissions according to plant protein source. This lack of variation is in accordance with previous publications reporting little variation in the GHG emission among different plant-based products [
22]. However, the presence of eggs in the analogs significantly increased the GHG emissions. Our results are consistent with other authors who reported that when animal ingredients are used in the production of the analogs, the GHG emissions increase [
33]. This is primarily because more GHGs are released during the production of animal-derived foods than the production of plant foods [
22].
Although some variation was seen among the various products (see
Table 1 and
Table 2), the nutritional analyses of the meat analogs showed no large differences in the nutrient profiles. The meat analogs contained a good supply of protein, about 20–25 g per 100 g, which represents 35–55% of the adult Daily Reference Value. They are all low in saturated fat (less than 2 g/100 g) and have no cholesterol. Sodium levels in 100 g portions of meat analogs averaged only about 7% to 12% of the upper limit of daily sodium intake. The meat analogs contained an average only 6–12 g fat/100 g portion. Because of the nutritional composition of soy [
46], the soy-based products are richer in omega-3 fatty acids and the important minerals iron and zinc. They also have greater levels of many of the B vitamins, as well as containing the health-promoting isoflavonoids. In addition, the amino acid profile of soy is a complete protein source, containing all nine essential amino acids necessary for human nutrition. As expected, the nut-based meat analogs were rich in the healthy monounsaturated fatty acids [
37], and regular nut consumption has been associated with health benefits in numerous studies [
47]. Nevertheless, the most favorable nutrient profile of soy- and nut-based products could not be relevant enough to differentially affect individual health, especially if consumption of meat analogs is integrated into a well-balanced diet.
Egg is used in the production of meat analogs for sensory attributes, rather than providing the main source of protein [
29]. It is worth highlighting the fact that while the presence of a small amount of animal-sourced ingredients (i.e., eggs) does not change the nutritional profile of our products, their presence results in a significantly higher carbon footprint.
Our results may have an immediate application. No major differences in carbon footprint and nutritional composition of meat analogs exist among products with differences in their main source of protein. This fact provides support to consumers who opt for a certain type of product, but who are at the same time aware of the sustainability and nutritional composition of their foods. In addition, the knowledge that total plant-based products are significantly less damaging to the environment than products with egg could be a factor to influence the consumer to choose an egg-free meat analog product.
The current study has some limitations. Our life cycle assessment only covers from farm to factory gate. Retailing, cooking and waste disposal go beyond the scope of the present report. Nevertheless, their inclusion would not seem to vary the main comparative results. On the other hand, a major novelty of the current study is that we are the first to report on primary data of the GHG emissions and nutritional values for a large number of commercially available plant protein-rich meat analogs, differentiating them by ingredient composition.
