A Polyphenol-Rich Olive Oil Byproduct-Derived Nutraceutical Preserves Muscle Health in Adults at Metabolic Risk: A Secondary Analysis of a Pilot Study

Background: Muscle function determines overall health and is often impaired in metabolic syndrome, largely due to oxidative stress and inflammation. Olive mill wastewater (OMWW) is rich in bioactive polyphenols (e.g., hydroxytyrosol, oleuperine and verbascoside) that may hinder these pro-sarcopenic mechanisms, representing a potential nutraceutical to maintain muscle health. Objective: To evaluate the effects of short-term supplementation with an OMWW-derived polyphenol extract (Oliphenolia®, OMWW-OL) on muscle-related parameters and antioxidant biomarkers in adults at metabolic risk, while maintaining dietary habits. Methods: This exploratory, hypothesis-driven secondary analysis was based on a single-arm longitudinal pilot study assessing patients at baseline (T0), after 30 days of s supplementation (T1), and 30 days post-discontinuation (T2). Anthropometry, bioelectrical impedance, and biochemical assessments were performed. Results: Supplementation was associated with modest increases in skeletal muscle mass, muscle mass percentage, and wrist, arm, and calf circumferences. Fat mass decreased progressively, while total body water percentage and hydration status improved. Ferritin levels rose at T2, alongside increases in protein thiols (PSH) and Trolox equivalent antioxidant capacity (TEAC), suggesting improved iron status and reduced oxidative stress. Body weight and BMI decreased, as expected in a dietary intervention for metabolic syndrome, while muscle health showed a tendency to improve. Conclusions: Although findings require cautious interpretation, short-term Oliphenolia® supplementation was associated with modest but consistent directional changes across musclerelated and metabolic indicators in adults at metabolic risk. The results support hypothesis generation and the need for larger studies aimed at investigating the potential preventive role of OMWW-OL in the context of cancer-associated sarcopenia.