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 and cancer, largely due to oxidative stress and inflammation. Olive mill wastewater (OMWW) is rich in bioactive polyphenols (e.g., hydroxytyrosol and verbascoside) that may hinder these potential pro-sarcopenic mechanisms, representing a potential nutraceutical to limit muscle health decline. 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 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 toward improvement. Conclusions: Although the findings require cautious interpretation, short-term OMWW-OL supplementation was associated with modest but consistent directional changes in muscle-related and metabolic indicators in adults at metabolic risk. The results support hypothesis generation and highlight the need for larger studies to further explore the potential role of OMWW-OL in the context of cancer-associated sarcopenia.