Research related to sustainable diets is is highly relevant to provide better understanding of the impact of dietary intake on the health and the environment. To assess the association between the adherence to an energy-restricted Mediterranean diet and the amount of CO emitted in an older adult population. Using a cross-sectional design, the association between the adherence to an energy-reduced Mediterranean Diet (erMedDiet) score and dietary CO emissions in 6646 participants was assessed. Food intake and adherence to the erMedDiet was assessed using validated food frequency questionnaire and 17-item Mediterranean questionnaire. Sociodemographic characteristics were documented. Environmental impact was calculated through greenhouse gas emissions estimations, specifically CO emissions of each participant diet per day, using a European database. Participants were distributed in quartiles according to their estimated CO emissions expressed in kg/day: Q1 (≤2.01 kg CO), Q2 (2.02-2.34 kg CO), Q3 (2.35-2.79 kg CO) and Q4 (≥2.80 kg CO). More men than women induced higher dietary levels of CO emissions. Participants reporting higher consumption of vegetables, fruits, legumes, nuts, whole cereals, preferring white meat, and having less consumption of red meat were mostly emitting less kg of CO through diet. Participants with higher adherence to the Mediterranean Diet showed lower odds for dietary CO emissions: Q2 (OR 0.87; 95%CI: 0.76-1.00), Q3 (OR 0.69; 95%CI: 0.69-0.79) and Q4 (OR 0.48; 95%CI: 0.42-0.55) vs Q1 (reference). The Mediterranean diet can be environmentally protective since the higher the adherence to the Mediterranean diet, the lower total dietary CO emissions. Mediterranean Diet index may be used as a pollution level index.