Efecto de una intervención intensiva basada en el consumo de dieta mediterránea hipocalórica en la sostenibilidad ambiental

Abstract

Introduction Climate change is one of the major issues of the 21st century and there are a growing number of strategies aimed at reducing human impact on the planet. Diet plays a key role in this regard, as food systems are considered to be responsible for one third of greenhouse gas (GHG) emissions, 60% of freshwater use and the use of about half of the planet's ice-free surface. Given that not all foods have the same environmental impact, the choice of different dietary patterns becomes fundamental in making the food system more sustainable, as the type of diet followed directly influences the quality and quantity of what is eaten and this conditions the individual environmental footprint generated. Current studies agree that dietary patterns with less animal-based foods and more plant-based foods, in addition to being healthier, have a lower environmental impact. One of the dietary patterns that meets these characteristics is the Mediterranean Diet (MedDiet), characterized by a high consumption of vegetable products and a low-moderate consumption of meat, poultry, and dairy products. This dietary pattern is recognized for its important benefits for cardiovascular health and the prevention of chronic diseases. In addition, since it reduces the intake of animal products and promotes biodiversity, this dietary pattern is expected to benefit environmental sustainability. Therefore, the main objective of this doctoral thesis is to assess the effect on environmental sustainability of an intensive intervention based on the promotion of a low-calorie MedDiet. Methods Information on dietary habits and lifestyles of 5800 participants from the PREDIMED-Plus study and 1554 participants from the EPITeen cohort was used. Food intake was estimated using semi-quantitative food frequency questionnaires validated in the Spanish and Portuguese population, and adherence to the MedDiet using the Dietary Score index. Based on the EAT-Lancet Commission tables, the influence of dietary intake on environmental impact (through five indicators: GHG, acidification and eutrophication potential, land, and energy use) was assessed. The association between adherence to the MedDiet and its environmental impact, as well as the association between the intervention and changes in each of the environmental factors was estimated using multivariate adjusted linear regression models. In addition, mediation analyses were performed to estimate the extent to which changes in each of the 2 intervention components, namely adherence to the MedDiet and calorie reduction, were responsible for the observed reductions in environmental impact. Results In the framework of the PREDIMED-Plus study, higher MedDiet adherence (high vs. low) was significantly associated with lower environmental impact both at baseline ((GHG (4895.8 vs. 5133.2 g/CO2-eq), land use (8.9 vs. 10.6 m2), energy use (8763.3 vs. 9682.3 kJ), potential acidification (59.0 vs. 69.8 g SO2-eq) and eutrophication (22.6 vs. 26.1 g PO4-eq)) and one year after remaining in the study ((GHG (4513.7 vs. 4776.0 g/CO2-eq), land use (6.8 vs. 8.4 m2), energy use (8004.9 vs. 8817.5 kJ), potential acidification (47.9 vs. 58.1 g SO2-eq) and eutrophication (18.1 vs. 21.5 g PO4-eq)). Meat products had the highest environmental impact on all factors analysed, although their consumption was reduced after one year of intervention, leading to a 6.5% reduction in GHG emission, 4.9% in energy use, 3% in acidification, 3.6% in eutrophication and 3.1% in land use. Furthermore, in the intervention group (IG) and after one year in the study, we observed a significant reduction in acidification levels (-13.3 vs. -9.9 g SO2-eq), eutrophication (-5.4 vs. -4.0 g PO4-eq) and land use (-2.7 vs. -1.8 m2). For GHG emissions and energy use, although a greater reduction was observed for IG, statistical significance was not reached (-377.7 vs. -345.1 g CO2-eq; and -899.7 vs. -787.9 kJ respectively). Adherence to MedDiet partially mediated the association between intervention and reduction of acidification by 15%, eutrophication by 10% and land use by 10%. Caloric reduction partially mediated the association with the same factors by 55%, 51% and 38% respectively. In addition, adherence to MedDiet fully mediated the association between intervention and reduction in GHG emissions by 56% and energy use by 53%. In the framework of the EPITeen study, higher adherence (high vs. low) to the MedDiet was associated with lower environmental impact in terms of land use (7.8 vs. 8.5 m2, p =0.002), potential acidification (57.8 vs. 62.4 g SO2-eq, p =0.001) and eutrophication (21.7 vs. 23.5 g PO4-eq, p <0.001). Energy use decreased only in the model adjusted for calorie intake (9689.5 vs. 10265.9 kcal, p <0.001), and GHG emissions were only reduced in a complementary model in which fish consumption was removed (3035.3 vs. 3281.2 g CO2-eq, p <0.001). In this study, meat products were also the food with the highest environmental impact for the five environmental factors analysed, contributing to 35.7% of total GHG emissions, 60.9% in energy use, 72.8% in land use, 70% in acidification and 61.8% in eutrophication. Conclusions In the Spanish adult population, participants with higher adherence to the MedDiet significantly reduced their environmental impact in terms of GHG emissions, acidification and potential eutrophication, land, and energy used after one year in the programme. After one year of intensive nutritional intervention with promotion of an energy reduced MedDiet, the IG participants reduced the most on all five indicators analysed, doing so significantly in terms of acidification, eutrophication, and land use. This improvement in environmental impact was partially mediated by increased adherence to the MedDiet and calorie reduction in participants' diets. In young Portuguese population, higher adherence to the MedDiet was associated with lower environmental impact in terms of acidification, eutrophication, and land use, and even lower GHG emissions and energy use depending on the adjustment model used. In both cases, meat products had the highest weight in terms of environmental impact in the five factors analysed, so diets low in these products are expected to be more environmentally sustainable.