Mediterranean diet cuts environmental impact and improves metabolic health, study finds

In a recent study published in the journal Science of the Total Environment, researchers investigated the environmental impact of a Mediterranean diet with reduced energy intake over one year in participants with metabolic syndrome.

Their results indicate that the intervention was linked to significant reductions in acidification, eutrophication, and land use, with diet adherence and caloric reduction playing key roles in mediating these environmental benefits.

Study: Effect of a nutritional intervention based on an energy-reduced Mediterranean diet on environmental impact. Image Credit: leonori / Shutterstock

Background

Climate change poses severe threats to public health, including rising temperatures, altered precipitation patterns, increased droughts, intensified heat waves, and heightened transmission of diseases like dengue and malaria.

It also impacts agriculture and livestock, reducing food quantity and quality. With the global population expected to reach nearly 10 billion by 2050, the need for food will escalate, intensifying the environmental impact of food systems, which are significant contributors to greenhouse gas emissions, eutrophication, acidification, freshwater use, and biodiversity loss.

The United Nations Food and Agriculture Organization defines sustainable diets as crucial for mitigating these impacts by promoting nutrition and food security while minimizing environmental damage.

Previous research indicates that diets lower in animal products and higher in plant foods are healthier and have a smaller environmental footprint. However, specific dietary interventions that can effectively reduce environmental impacts need to be explored.

About the study

This study addressed existing research gaps by examining the environmental benefits of a Mediterranean diet with reduced energy intake in older Spanish adults with metabolic syndrome. It focused on its potential to decrease greenhouse gas emissions, acidification, eutrophication, and land use.

This study utilized data collected during the PREDIMED-Plus trial, a multicentre, randomized (non-blinded) eight-year study conducted in Spain. The trial included 6,874 participants, aged 55-75 for men and 60-75 for women, all with metabolic syndrome but without any cardiovascular disease in their medical history.

Participants had a body mass index (BMI) between 27 and 40 kg/m² and met three or more criteria for metabolic syndrome. They were randomly allocated to either an intervention group, which received a Mediterranean diet (MedDiet) with reduced energy and guidelines for physical activity and behavioral therapy, or a control group, which received advice about MedDiet without weight loss promotion.

Dietary intake was assessed using a validated 143-item Food Frequency Questionnaire (FFQ), and dietary adherence was measured using the Panagiotakos Diet Score. Environmental impact indicators, including emissions of greenhouse gases, energy use, land use, acidification, and eutrophication, were calculated based on the EAT-Lancet Commission tables.

Data were analyzed using linear regression modeling that adjusted for sex, age, education level, and baseline caloric intake. A mediation analysis was conducted to determine the extent to which changes in caloric intake and adherence to the diet mediated the reduction of environmental impact.

Findings

The study found significant decreases in environmental effect factors between the intervention and control groups. Specifically, the intervention group showed greater reductions in acidification (−13.3 compared to -9.9 g of sulfur dioxide equivalent), eutrophication (−5.4 compared to -4.0 g phosphate equivalent), and land use (−2.7 compared to -1.8 m²).

Additionally, IG experienced significant decreases in caloric intake (−178.4 compared to -73.3 kilocalories) and higher dietary adherence for the intervention group (1.2 compared to 0.5 points).

Meat was the main contributor to environmental impact factors in both groups, while fish and seafood contributed more to greenhouse gas emissions in IG.

The mediation analysis showed that caloric reduction partially mediates the observed relationship between intervention and reductions in acidification, eutrophication, and land use, explaining 55%, 51%, and 38% of the overall association, respectively.

Adhering to the diet also partially mediated the relationship between these factors, with full mediation for greenhouse gas emissions (56%) and energy use (53%).

Conclusions

This study underscores the positive impact of a one-year MedDiet intervention with reduced energy intake on environmental sustainability, particularly in reducing acidification, eutrophication, and land use.

It innovatively explores the role of caloric reduction and adherence to MedDiet in mediating this relationship, a novel approach in the field. Despite limitations such as data variability and potential recall bias, the study’s strengths lie in its real-world assessment of environmental impact and its large sample size.

The findings highlight the potential of MedDiet interventions to mitigate environmental damage, especially concerning meat consumption. However, challenges remain in standardizing environmental impact databases and accounting for regional variations.

Future research could expand on these findings, exploring broader dietary patterns and their environmental implications, fostering a deeper understanding of the diet-environment-health trilemma, and promoting sustainable nutritional choices.

Overall, this study underscores MedDiet interventions’ potential to enhance human health and environmental sustainability.