Dietary Strategies to Reduce Environmental Impact: A Critical Review of the Evidence Base

Abstract

The food system is a major source of environmental impact, and dietary change has been recommended as an important and necessary strategy to reduce this impact. However, assessing the environmental performance of diets is complex due to the many types of foods eaten and the diversity of agricultural production systems and local environmental settings. To assess the state of science and identify knowledge gaps, an integrative review of the broad topic of environment and diet was undertaken, with particular focus on the completeness of coverage of environmental concerns and the metrics used. Compared with the 14 discrete environmental areas of concern identified in the United Nations Sustainable Development Goals, the located journal literature mainly addressed greenhouse gas (GHG) emissions and, to a lesser extent, land and water use. Some relevant concerns were rarely addressed or not addressed at all. In the case of GHG emissions, changes in land use and soil carbon stocks were seldom considered. This represents a disconnect between the science informing strategic climate action in the agricultural sector and the science informing public health nutrition. In the case of land and water use, few studies used metrics that are appropriate in a life-cycle context. Some metrics produce inherently biased results, which misinform about environmental impact. The limited evidence generally points to recommended diets having lower environmental impacts than typical diets, although not in every case. This is largely explained by the overconsumption of food energy associated with average diets, which is also a major driver of obesity. A shared-knowledge framework is identified as being needed to guide future research on this topic. Until the evidence base becomes more complete, commentators on sustainable diets should not be quick to assume that a dietary strategy to reduce overall environmental impact can be readily defined or recommended.

Which Diet Has the Least Environmental Impact on Our Planet? A Systematic Review of Vegan, Vegetarian and Omnivorous Diets

“…It suggests that a reduced consumption of animal-based products, and an increased vegetable intake show lower GHGEs [18]. This statement is supported by multiple other studies with diets having an increased environmental impact when increasing the animal-based food intake [15,19]. Diets with low meat and low processed food consumption have lower GHGEs than their counterparts [20].…”

“…One study finds that the difference between water inputs for animal protein vs. plant protein is normally around a factor of 26; even when intensive irrigation is needed for plant-based protein, animal protein production requires 4.4 times as much water [22]. A second study supports this finding, stating that production for LOV diets has increased the water-scarcity footprint by 26% [15]. Nevertheless, it is difficult to make general scientific claims, since studies regarding metrics of water use are based on very limited evidence [23].…”

“…Based on self-reported dietary patterns in the UK, high meat consumers were responsible for 1.9 times and average meat consumers were responsible for 1.5 times more GHGEs than people on LOV diets [12], and 2.5 and 2 times more GHGEs, respectively, than vegan consumers [12]. One study concludes that, if the beef, dairy, pork, poultry and eggs consumed in an average European diet were reduced by 50% of and replaced with a 50% higher bread intake, the amount of GHGEs emitted could be reduced by over one-third [15].…”

The Environmental Foodprint of Obesity

“…Current dietary guidelines advocate more plant‐based, sustainable diets based on scientific evidence about diet–health relationships but also to address environmental concerns . However, and despite considerable efforts to date , the evidence base regarding the environmental impact of various dietary patterns is largely incomplete . Our analysis indicates that, in future sustainable diet modeling, more attention needs to be given to the contribution of CO 2 emissions from obesity per se, and sustainability aspects should also be included in the diet–health relationship estimations.…”

Analysis of the Current Agricultural Production System, Environmental, and Health Indicators: Necessary the Rediscovering of the Pre-hispanic Mesoamerican Diet?

“…Our dietary choices modify the incidence of NCD, as well as the agricultural systems that supply the raw material for food production. The inclination toward diets rich in sugars and highly processed foods can have detrimental environmental effects such as the increase of GHGe (Ridoutt et al, 2017), deforestation, biodiversity loss (Myers et al, 2017), and water waste (Tom et al, 2016). In addition, these dietary patterns also affect other climate change related factors like temperature rise and excessive landuse change (close to 70%), while hindering the right of countries to exercise their food security and sovereignty (Whitmee et al, 2015).…”