Effects of a Short‐Term Vegan Challenge in Older Adults on Metabolic and Inflammatory Parameters—A Randomized Controlled Crossover Study

SCOPE: A long-term vegan diet carries the risk of insufficient protein and micronutrient intake for older adults. However, even a short-term (48 h) vegan diet exerts positive metabolic effects in younger adults. In this study, we investigate the feasibility and effects of a short-term vegan challenge on metabolic and inflammatory markers in older adults. METHOD AND RESULTS: In this randomized controlled crossover-study, 30 healthy older adults (≥65 years) are assigned to either a 48 h ad libitum vegan or omnivorous diet. During the vegan diet, participants exhibit lower protein (p = 0.001) and fat intake as well as higher carbohydrate and dietary fiber intake, resulting in a lower caloric intake (all p < 0.001). Insulin concentrations (p = 0.042) and insulin resistance (p = 0.036) decline only after the vegan diet. The study observes reductions in serum glucose (p < 0.001), triglyceride (p = 0.005), and hsCRP (p = 0.044) concentrations and weight (p < 0.001), independent of the diet. Participants with low-grade inflammation exhibit notable metabolic improvements after the vegan diet. CONCLUSION: Improvements in insulin homeostasis are observed after the vegan diet, but meeting protein requirements are not feasible during the short-term vegan challenge despite dietary counseling, which warrants concern.