Global Warming Reduction by Switching to Healthy Diets

by Shelby Long

The consumption of food and beverages accounts for 22–31% of total private consumption greenhouse gas (GHG) emissions in the EU (Tukker et al. 2009). More specifically, the production of meat and dairy products tend to produce greater GHG emissions (Audsley et al. 2009). Saxe et al. (2012) examine how different diets, which are composed of different foods, are associated with varying potential GHG emissions. They use consequential Life Cycle Assessment to compare the emissions, or global warming potential (GWP), from food production for an Average Danish Diet (ADD), the Nordic Nutritional Recommendations (NNR), and a New Nordic Diet (NND), which was developed by the OPUS Project. They determined that the GHG emissions association with NNR and NND were lower than those associated with ADD, by 8% and 7%, respectively. When taking into account the transport of food, NND emissions are 12% less than ADD emissions. With regard to organic versus conventional food production, GHG emissions are 6% less for NND than for the ADD. Saxe et al. adjusted NND to include less beef and more organic produce, and they substituted meat with legumes, dairy products, and eggs, which made the diet more climate-friendly. As a result of this adjustment, the GHG emissions associated with NDD was 27% less than emissions for ADD.

Saxe et al. adjusted the energy and protein content for the NNR and NND accordingly in order to make them contain the same amount of energy and protein per person per year as ADD. This adjustment was made so the GWP for the three different diets could be determined more easily. In order to calculate the GHG of the different diets authors used consequential life cycle assessment (cLCA). They used 1 kg of produced food or beverage available at the supermarket as the functional unit for their calculations. The calculations included GHG emissions produced by all production activities, from soil to supermarket. In order to determine the carbon footprint of the various food items, researchers used the Danish LCA Food Database. They used the ISO standard 14040 to calculate the Potential GHG emissions for the various products. The Average Danish Diet is used as a reference to which the two Nordic diets, NNR and NND, are compared. The ADD is composed of more than 300 food and beverage products that are available to the average Dane household. The NNR is a modified version of the ADD based on the Nordic Nutrition Recommendations. The NND is inspired by olden day Nordic diets with a higher content of roots, berries, nuts, fish, whole grain products, and less animal produce than the Average Danish Diet. The NND was intended to be a healthy, appetizing, and sustainable diet of Nordic origin that is based on the Danish dietary guidelines and the OPUS dietary recommendations. All food and beverages included in the NND are locally produced and 75% of the food products are organically produced.

Saxe et al. tested eight scenarios to determine the varying GWP between the three diets. Scenario 1 examined the varying GWP of the three diets based on the differing food items that make up the diets. Scenario 2 and later scenarios incorporate GHG emissions produced during international transportation of the imported products for the ADD and the NNR. In order to calculate the emissions for the international transportation, researchers combined data for distance transported from the producer country to the midpoint of Denmark, the means of transportation, and the amount of cooling and freezing of the produce during transportation. The NND only includes local products, and, therefore, only local transportation GHG emissions are included. Scenario 3 and later scenarios include variation in GHG emissions based on whether food was produced organically or conventionally. The GHG emissions of the NND were reduced by 11 organic food items, including beer, coffee, dairy products, lamb, pasta, rapeseed oil, pork, potato, oats, rye bread, and whole wheat products. The GHG emissions of the NND were increased by seven organic food items, including apples, beef, carrots, chicken, eggs, non-alcoholic beverages, and tomatoes. Based on these 18 organically-produced food items, researchers determined that 80% of the NND is composed of organic products. Saxe et al. applied the actual national ration between organically and conventionally produced food and beverages to the ADD and the NNR, which results in a content of 6.6% organic products for both diets. Scenarios 4 and 5 include a change in the composition of meat while weight, energy, and protein are held constant. Scenarios 6 and 7 include a change in the content of organic produce. For Scenario 6, researchers reduce the organic produce content in the NND to 6.6%. Scenario 7 excludes the seven products that increased the GHG emissions in Scenario 3. Scenario 8 includes 2 times more dairy products, 1.6 times more eggs, 1.5 times more cheese, and 10 times more legumes in order to substitute meat, fish, and seafood with other protein-rich foods. In Scenario 8 researchers exclude alcoholic beverages, sweets, butter, and convenience foods.

Saxe et al. determined that in Scenario 1, the variation in foods that make up the NNR and the NND leads to a reduction in GHG emissions by 8% and 7% respectively, compared to the ADD. Under Scenario 2, transportation-associated GHG emissions were reduced by 7% and 12% for the NNR and the NND, respectively, compared to the ADD. Applying the 6.6% organic product content to the ADD and the NNR did not seem to have much of an effect on their GHG emissions. Researchers suggest that this is the case because the inclusion of foods that increase and foods that decrease GHG emissions resulted in a counter-balancing effect. They also found under Scenario 3 that when 80% of the conventional produce is substituted with organic produce in the NND, emissions increase from 130 kg to 1920 kg CO2eq/person/year. The GWP associated with the NND in Scenario 3 increases, and, therefore, is only 5.7% better with respect to GHG emissions than the ADD. Scenarios 4–8 highlight the large contribution animal produce makes to GHG emissions, as they make up over half of the total GHG emissions. Scenario 4 suggests that with less beef and more chicken, and other types of meat being included in the NND, the GHG emissions can be reduced by 170 kg, or 14%. With the same changes to meat produce being employed under Scenario 5, GHG emissions can be reduced by 270 kg, or by 19%. Under Scenario 6, GHG emissions were 25% lower than the ADD of Scenario 3 when the organic produce content in the NND was reduced to 6.6%. Under Scenario 7, GHG emissions associated with the NND were reduced by 27% compared to the ADD reference of Scenario 3 when only the 11 GHG emission reducing organic products from Scenario 3 were included. GHG emissions were reduced by 27% under Scenario 8, which is the same as the reduction in Scenario 7.

Saxe et al. assert that under the two Nordic diets assessed, the NNR and the NND, the GWP of eating and drinking is improved by 6–7%, relative to the average Danish diet (ADD). The livestock sector is a major contributor to greenhouse gas emissions, and, therefore, it is an important area of study. Saxe et al. identifies six lessons for developing healthy and sustainable diets. Lesson 1 stresses the importance of reducing meat and dairy product intake, especially beef, to minimize the GWP of diets. Lesson 2 indicates that local production of food reduces GWP associated with transportation and cooling or freezing. Lesson 3 suggests that the substitution of conventionally produced products with those that are organically produced often leads to negative impacts on GWP. A wide range of studies offers differing results about whether organically-produced products negatively or positively impact GWP. Lesson 4 indicates that the composition of meat in a diet significantly affects its GWP, and eating less red meat and more white meat tends to reduce the GWP of the NND by 9 to 14%. Lesson 5 suggests that beer, wine, and alcohol contribute 9%, sweets and candy contribute 7%, and coffee, tea, and cocoa contribute 6% to the total GWP of the ADD. Lesson 6 indicates that a vegetarian diet does not necessarily reduce the GWP associated with a particular diet more than an optimized omnivorous diet, which is illustrated by Scenarios 7 and 8.

Saxe et al. assert that the total impact of food and beverage production on climate change is underestimated because land use change, which partly results from population growth and increases in demand for organic foods, was not taken into account in this study. The researchers suggest that differential taxes on various foods may direct people to adopt more healthy and sustainable diets; however, these types of taxes receive much political opposition. OPUS developed the NND with the goal of including easily available ingredients that positively impact peoples’ health. The development of diets that are healthy and sustainable plays an important role in the future of climate change mitigation.

Saxe, H., Larsen, T., Mogensen, L., 2012. The global warming potential of two healthy Nordic diets compared with the average Danish diet. Climatic Change 116, 249–262. http://link.springer.com/article/10.1007/s10584-012-0495-4

Audsley et al. 2009. How low can we go? An assessment of greenhouse gas emissions from the UK food system and the scope to reduce them by 2050. Cranfield University, UK.

Tukker et al. 2009. Environmental impacts of diet changes in the EU. European Joint Research Centre. Institute of Prospective Technological Studies.

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