vital: vaccination, immunity, time-restricted eating, aging and lifestyle

Conditions: Vaccination; Immunosenescence; Metabolism

Summary: the aim of this study is to investigate the effects of a four-week time-restricted eating (tre) intervention on autophagy, immune function, and vaccine response to a seasonal influenza vaccine in older healthy subjects.

aging impairs immune cell autophagy and reduces vaccine efficacy, leaving older adults highly vulnerable to influenza. time-restricted eating (tre), by limiting daily food intake to an 8-hour window without detailed calorie counting, modulates nutrient-sensing pathways (e.g., mtor inhibition, ampk activation) and boosts autophagic flux in preclinical models. in a randomized, controlled trial, healthy volunteers aged 60-85 will follow either four weeks of tre or their usual eating pattern. after that, all will receive a standard seasonal influenza vaccine outside of the trial at their general practitioner (min. 2 days and max. 14 days after the stop of intervention). blood and physiologic measurements at baseline, after four weeks of study intervention will quantify autophagy in immune cells, metabolome/proteome shifts, body composition, blood pressure, and arterial stiffness, among others. at two additional visits after the vaccination (2 weeks and 12-14 weeks after the vaccination), immune responses to the vaccination will be monitored in the blood. the investigators hypothesize that tre-induced restoration of autophagy and amelioration of immunosenescence will correlate with stronger vaccine responses, offering a simple, low-cost strategy to rejuvenate immunity and improve preventive care in the elderly.

Eligibility criteria:
inclusion criteria: * male and female participants, enrolled in a 1:1 ratio * age 60-85 years * body mass index (bmi) 20-35 kg/m² * capacity to give informed consent * existing health insurance to allow evaluation and treatment of any incidental findings * usual daily eating window \> 11 hours * first meal of the day before 10:00 am * willingness to receive seasonal influenza vaccination and proof of scheduled appointment * willingness and ability to follow a prescribed tre dietary regimen (8-hour daily eating window; 16-hour fast without any caloric intake) * influenza-vaccination appointment pre-arranged with primary care physician and coordinated with study team to align with tre intervention exclusion criteria: * any vaccination (especially influenza) within 6 months before intervention start * influenza infection within 6 months before intervention start * history of severe adverse reactions to prior vaccinations * symptoms of systemic inflammatory or autoimmune disease * immunosuppression (including use of immunosuppressive drugs) * severe hypertension (systolic \> 180 mmhg or diastolic \> 110 mmhg) * any medical condition or functional impairment that, in the investigator's judgment, precludes safe participation * participation in any fasting intervention (e.g., tre, alternate-day fasting, 5:2, 18:6) within 6 months before enrollment * participation in another diet or weight-loss program (e.g., intensive athletic training) * night-shift or rotating-shift work * severe, active, or unstable medical conditions requiring treatment * chronic use of prescription medications (except hormonal contraception) * postoperative recovery phase * antibiotic therapy within 3 months before enrollment * acute or chronic infections * therapeutic or medically prescribed special diets * food intolerances * vegan diet * current smoker * weight change \> 2 kg in the month before enrollment * known substance, drug, or alcohol abuse * anemia * claustrophobia * legal incapacity or any other circumstance that prevents full understanding of the nature, importance, and implications of the study

Keywords: fasting vaccination intermittent fasting time-restricted eating influenza immunity aging immunosenescence