OPTIPROT, Targeted Precision Nutrition for Protein Needs in Ageing

Inclusion Criteria * Women or men * Age: ≥ 50; ≤ 75 years * BMI: 18.5-35 kg/m² and stable weight for at least 3 months (without weight gain or loss \>3 kg). * Ability to read, write, and speak in Catalan or Spanish. * Signing of the informed consent form. Exclusion Criteria * Age ≤ 49 or ≥ 76 years * BMI: ≤18.5; ≥ 35 * Pregnant or lactating women * Presence of chronic or autoimmune disease or metabolic condition that significantly alters nutritional requirements, such as: type I diabetes, celiac disease, inflammatory bowel disease, chronic kidney disease, severe liver disease, uncontrolled thyroid disorders, cancer, food allergies or intolerances, musculoskeletal disorders, moderate or severe cognitive impairment, or immobilization in the last 6 months. * Alcohol consumption:Men: Consuming 4 or more Standard Drink Units (SDUs)\* per day or 28 SDUs per week. Women: Consuming 2 or more Standard Drink Units (SDUs)\* per day or 17 SDUs per week. * Individuals currently participating or who have participated in a clinical trial involving medications or nutritional intervention within the last 30 days before study inclusion. * Recent use of antibiotics in the last two weeks.