Elsevier

Science of The Total Environment

Volume 644, 10 December 2018, Pages 77-94
Science of The Total Environment

Review
Carbon footprint and nutritional quality of different human dietary choices

https://doi.org/10.1016/j.scitotenv.2018.06.339Get rights and content

Highlights

  • A detailed analysis of 21 peer-review studies was performed following specific criteria.

  • 66 dietary choices were compared considering their carbon footprints.

  • Nutritional quality was assessed in specific scenarios according to data availability.

  • Dietary choices rich in vegetables had lower carbon footprints than meat-rich ones.

  • Reducing animal products can be environmentally favourable but limit some nutrients ingestion.

Abstract

Apart from industrial activities, our eating habits also have a significant environmental cost associated with crop cultivation, manufacturing processes, packaging, refrigeration, transport cooking and waste management. In a context of growing social awareness of the role of different dietary choices in the environment, the review of different alternatives on the road to a healthy and sustainable diet should integrate relevant information on the nutritional quality of different eating habits. Since dietary choices have an effect on environmental sustainability and human health, a literature review on different dietary choices has been conducted to determine the differences in carbon footprint and nutritional quality identifying the main hotspots trying to give advice towards the identification of sustainable diets. After applying a set of criteria for reference selection, 21 peer-reviewed studies have been analysed in detail, allowing the comparison of 66 dietary scenarios.

We identified that the so-called Mediterranean and Atlantic diets present high nutritional scores and low carbon footprints. On the contrary, the dietary choices identified in northern and Western Europe, as well as in the United States, have the highest carbon footprints, highlighting the contribution of dairy products as a basic source of high-quality nutrients and protein. Broadly speaking, dietary choices rich in vegetables (e.g., vegan, vegetarian as well as Indian and Peruvian) have a better environmental profile than those rich in meat (mainly ruminant meat). In line with these findings, the shift in meat consumption habits from beef and veal to chicken, pork and poultry, the introduction of alternative foods to animal protein (e.g. quinoa) and the consumption of olive oil as a major source of vegetable oil may be compatible with a healthier and more environmentally friendly diet. However, the complete elimination of meat and dairy products from the daily diet may not be feasible in case the supply of some micronutrients (e.g., calcium and vitamin D) is not guaranteed. Limitations were identified in the consulted studies related to the consideration of the different system boundaries, as well as underlying uncertainties related to data sources. Therefore, efforts should be made to develop consistent and agreed-upon methods for estimating both the carbon footprint and nutritional quality scores.

Introduction

Food production and consumption involves a complex system that includes a wide range of stages such as agricultural and livestock activities, processing, distribution, preparation, consumption and waste management (Duchin, 2005; Friel et al., 2009). It is important to note that the number of calories that an average person needs daily depends on several factors, such as minimum and average dietary energy requirements (Vázquez-Rowe et al., 2017), level of activity, lifestyle, gender, age, weight, geographic location and cultural aspects (EFSA, 2009). Differences in eating habits can be found between countries, influenced by different levels of development and food security, as well as cultural and regional preferences (De Ruiter et al., 2014; Van Kernebeek et al., 2014). Access to healthy and adequate food consumption patterns depend on factors such as lifestyle, marketing and economic factors (Hawkesworth et al., 2010; Heller et al., 2013; Chaudhary et al., 2018). The relevance of the link between the diet choice, longevity and health is well known (Friel et al., 2009; Thaler et al., 2015). Diets rich in salt, saturated fat and free sugars are examples of unhealthy dietary choices (Hawkesworth et al., 2010). In this sense, the low incidence of cardiovascular diseases in Mediterranean countries has partially been attributed to their dietary habits (Menotti et al., 1990; Duchin, 2005; Estruch et al., 2006). The well-known Mediterranean diet is predominantly a plant-based diet, rich in fruits, vegetables and nuts, with moderate consumption in olive oil as fat source, as well as low in meat, added sugars, saturated fatty acids and salty snacks (Castañé and Antón, 2017; Rosi et al., 2017). In this sense, Western diets are based on a high intake of meat, dairy products and eggs, which implies a higher intake of saturated fat that exceeds nutritional recommendations (Tukker et al., 2011; Westhoek et al., 2014).

Another increasingly important issue is the relationship between dietary patterns, resource consumption and environmental impacts (Tilman and Clark, 2014). Consumers need to be informed about the environmental sustainability of their purchasing options to identify the most environmentally friendly dietary choice (Wallén et al., 2004). The food system is considered one of the most important sectors in terms of negative environmental impacts, mainly associated with Greenhouse Gases (GHG) emission, water requirements and land use (Friel et al., 2009; Tukker et al., 2011; Wolf et al., 2011; Gustafson et al., 2016). Approximately 50% of all GHG emissions from the food system are related to farming activities (Friel et al., 2009), which is mainly attributed to emissions of nitrous oxide (production of forage crops), methane (enteric fermentation) and carbon dioxide (land-use change associated with agriculture). In this framework, plant-based diets (lactoovovegetarian) are considered more environmentally friendly compared to those containing resource-intensive products, i.e., meat-rich diets (Baroni et al., 2007; Risku-Norja, 2011; Tilman and Clark, 2014; Van Kernebeek et al., 2014; Perignon et al., 2017). In this sense, research studies focusing on the design of more environmentally sustainable food production chains underscore the need to promote more sustainable eating patterns (Stehfest et al., 2009; Röös et al., 2015; Perignon et al., 2017). Food intake from a healthy perspective should reduce the consumption of foods of animal origin (specifically beef and pork) and increase those of plant origin (Stehfest et al., 2009; Thaler et al., 2015). Therefore, the definition of a sustainable future food pattern could be linked to a change in the diet from a meat-based to a plant-based diet (Garnett, 2011; Perignon et al., 2017). However, environmental sustainability must be in line with the maintenance of an overall healthy nutritional status (Gustafson et al., 2016).

Regarding the estimation of the environmental impact of dietary habits and/or daily diets, it is generally quantified on the basis of Life Cycle Assessments (LCA) data. It is a widely used and standardized tool for the systematic evaluation of the environmental aspects of a product or production system throughout all stages of its life cycle (ISO 14040, 2006), and is considered an ideal instrument for assessing the environmental dimension of sustainability. The definition of the system boundaries, the data managed, the functional unit and other uncertainties inherent to the method are factors that should be established specifically for comparative studies.

In the framework of a Life Cycle study, the carbon footprint is considered as and the fight against the effects of climate change. Numerous studies can be found in the literature that consider the environmental footprint (mainly carbon footprint) of European food consumption patterns following a LCA framework (Heller et al., 2013; Van Kernebeek et al., 2014) and even environmental-friendly strategies (e.g., refusal of air-transported products, promotion of organic production, partial substitution of meat by plant-based food or dairy products) have been proposed (Jungbluth et al., 2000; Hallström et al., 2015). In the framework of a LCA study, the carbon footprint is considered as an indicator of environmental impact that reflects the broad scientific and social awareness on the reduction of GHG emissions aiming to counteract the effects of climate change.

In this study, the carbon footprint, nutritional quality (in terms of Nutrient Rich Diet 9.3 score, NRD9.3) and daily energy intake (i.e. kcal) of different dietary options (daily diets) worldwide are assessed and compared for several reasons: 1) to determine the relationship between these items (when possible), 2) to identify differences in the same dietary pattern (i.e., vegan and vegetarian diets) between regions, 3) to answer the question whether eating less meat is more environmental friendly while maintaining nutritional recommendations and 4) to demonstrate the potential environmental benefits of introducing alternative foodstuffs (e.g., superfood) to replace meat consumption.

To do so, a detailed review has been performed considering the LCA-based studies available in the literature. To address the comparison, different methodological aspects of food-specific LCA (definition of diet, scope and boundaries) have been established from the consumption perspective, following the recommendations of Heller et al. (2013).

Section snippets

Literature search strategy

It is well known that there are remarkable differences between countries around the world in dietary choices. Therefore, the consideration of a representative diet (e.g., European diet) is not realistic. Different data sources are available that provide information on world food consumption through surveys, household economic expenditure data and food balance sheets from national import and export statistics (Tukker et al., 2011; Vázquez-Rowe et al., 2017). To ensure scientific quality and

Carbon footprint of selected dietary scenarios

In this study, GHG emissions (in kg CO2eq·person−1·day−1) were used to compare the environmental impact of different food consumption habits. However, there is a limitation related to the methodological approach considered for the estimation of this environmental impact, i.e. the system boundaries. In LCA studies, the system boundaries define the processes or activities included or excluded from the analysis. Although a consumption perspective was considered in all scenarios and only daily

Conclusions

What we eat plays an important role in assessing the sustainability of people's lifestyles. This review has largely focused on benchmarking the carbon footprint and nutritional quality of the dietary choices available in the literature. This study shows that diets with a high nutritional score based on the NRD9.3 score, such as Mediterranean and Atlantic diets, as well as vegetarian diets, also have high sustainability scores (i.e. low carbon footprints). Indian and Peruvian diets report the

Acknowledgements

This research has been supported by a project granted by Xunta de Galicia (project ref. ED431F 2016/001). Dr. S. González-Garcia would like to express her gratitude to the Spanish Ministry of Economy and Competitiveness for financial support (Grant reference RYC-2014-14984). The authors belong to the Galician Competitive Research Group GRC 2013-032 as well as to CRETUS (AGRUP2015/02), co-funded by Xunta de Galicia and FEDER (EU).

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