Estimation of GHG emission related to daily food intake among Koreans and its association with the metabolic syndrome based on the KNHANES (2016-2018) and the KoGES

Abstract

This study systematically explored various aspects of greenhouse gas (GHG) emissions associated with food consumption. It is known that approximately a quarter of climate change is attributed to GHGs generated in the entire food production-to-consumption process, representing half of the total carbon emissions. Despite this significant contribution, global efforts to reduce GHG emissions related to food have been relatively inadequate. Nonetheless, global efforts to reduce GHG emissions generated by the food sector remain largely insufficient. While there have been studies in Korea that aimed to quantify GHG emissions associated with food, these studies primarily concentrated on emissions stemming from livestock production and consumption. Notably, there is a dearth of research that assesses GHG emissions attributed to specific foods or food groups using data from the Korea National Health and Nutrition Survey (KNHANES). Moreover, no prior studies have analyzed the correlation between GHG emissions resulting from xviii dietary choices and the occurrence of metabolic syndrome (MetS). This gap in research can be attributed to the absence of a comprehensive and validated database specialized in food-related GHG emissions. Consequently, the primary objective of this study is to create a robust GHG emissions database tied to specific foods, utilizing data derived from the KNHANES. Subsequently, we plan to investigate the connection between these emissions, as calculated through this database, and the Korean Genome and Epidemiology Study (KoGES) cohorts' incidence of MetS. The process involved conducting a literature review of 3,894 food items, focusing on studies that utilized GHG emission coefficients obtained from life cycle assessment or data derived from reliable sources such as National data. The database underwent an assessment of uncertainty through Monte Carlo Markov Chain (MCMC) analysis for all 3,894 food items. With this verified database, the study examined the GHG emissions resulting from food consumption among Koreans using the KNHANES. The investigation involved the selection of 920 unique articles, resulting in the extraction of 300,420 food item values. The collected number of GHG emission factor values ranged from 0 to 788, and the study calculated average values for each food item, covering emissions at every stage of the food production process, including farming, processing, retail, cooking, and waste. The MCMC simulation confirmed that all food items in the database had acceptable levels of uncertainty. The results indicated that, on average, approximately 5.083 kg of CO2 equivalent (CO2eq) were emitted per day per person among the 21,271 Koreans surveyed, with men emitting 5.973 kg/CO2eq and women emitting 4.188 kg/CO2eq. Younger age groups tended to emit more due to their dietary choices. These emissions contributed to a total of 96 million carbon tons per year, equivalent to around 15.99% of the annual carbon emissions related to food. The most common food group associated with emissions was meat, followed by beverages, and grains. In a global context, per capita food intake typically results in the production of 2.2 tons of GHGs per year, equivalent to approximately 6.03 kg of CO2eq per day. The study attributes Korea's relatively lower emissions to its dietary patterns, which are less focused on meat and dairy products and more on vegetables like grains and kimchi. Furthermore, the study analyzed data from 11,294 participants in the Cardiovascular Disease Association Study (CAVAS), 44,752 individuals from the Health Examinee (HEXA) study, and 56,046 participants from the integrated cohorts to investigate the incidence of MetS. While the integrated population and CAVAS did not yield significant results, the HEXA study showed that diets associated with higher GHG emissions were linked to a greater incidence of MetS (incidence risk ratio (IRR): 1.07, 95% confidence interval (95% CI): 1.00 - 1.16). Factor analysis conducted in both cohorts revealed that pattern that consuming dairy moderately and vegetable-based diet had a lower incidence of MetS (IRR, 95% CI: 0.85, 0.75-0.98 in CAVAS; 0.87, 0.81-0.94 in HEXA). In contrast, pattern that primarily consuming meat had an increased incidence of MetS in the HEXA study (IRR, 95% CI: 1.13, 1.05 - 1.22). Observing a specific meat consumption level, roughly 0.67 times that in CAVAS compared to HEXA, may not harm individuals in this age group. HEXA indicates a significant positive relationship only in the highest quintile group, suggesting the need to reduce intake in that group rather than for all subjects. It's crucial to advocate for an appropriate amount within each food group, considering individual characteristics, as categorizing a diet as universally good or bad proves challenging. This comprehensive database of food-related GHG emissions can be linked with dietary data collected at all levels in the KNHANES, enabling the calculation of the environmental impact of individual and group diets. Through analysis in the KoGES cohorts, this study can offer valuable insights into dietary guidelines and other policies aimed at improving dietary habits and reducing food-related GHG emissions. Consequently, this study may serve as a useful tool for informing health and environmental policies.