Mediterranean diet reduces 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 show that the intervention was associated with significant reductions in acidification, eutrophication, and land use, and that dietary adherence and caloric reduction played 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 serious threats to public health, including rising temperatures, changing weather patterns, increased drought, more intense heat waves, and increased transmission of diseases such as dengue and malaria.

It also affects agriculture and livestock, reducing the quantity and quality of food. With the global population expected to reach almost 10 billion by 2050, the need for food will increase, which will increase the environmental impact of food systems, which contribute significantly to greenhouse gas emissions, eutrophication, acidification, freshwater use, and biodiversity loss.

The Food and Agriculture Organization of the United Nations defines sustainable diets as critical to mitigating these impacts by promoting nutrition and food security and minimizing environmental damage.

Previous research shows 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 among Spanish older adults with metabolic syndrome. It focused on its ability to reduce greenhouse gas emissions, acidification, eutrophication and land use.

This study used data collected during the PREDIMED-Plus trial, an eight-year randomized (non-blinded) multicenter 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 no 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 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 promoting weight loss.

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 greenhouse gas emissions, energy use, land use, acidification and eutrophication, were calculated based on the EAT-Lancet Commission tables.

Data were analyzed using linear regression modeling 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 dietary adherence mediated the reduction in environmental impact.

Results

The study found significant reductions in environmental effect factors between the intervention and control groups. Specifically, the intervention group showed greater reductions in acidification (−13.3 versus −9.9 g of sulfur dioxide equivalent), eutrophication (−5.4 versus −4.0 g of phosphate equivalent), and land use (−2.7 in compared to -1.8 m).²).

In addition, there were significant reductions in IG caloric intake (−178.4 versus −73.3 kilocalories) and higher adherence to diet for the intervention group (1.2 versus 0.5 points).

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

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 total association, respectively.

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

Conclusions

This study highlights 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 examines the role of caloric reduction and MedDiet adherence in mediating this relationship, a new 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 results highlight the ability of MedDiet interventions to mitigate environmental damage, particularly with regard to meat consumption. However, challenges remain in standardizing environmental impact databases and accounting for regional variations.

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

Overall, this study highlights the potential of MedDiet interventions to improve human health and environmental sustainability.