Development, Nutritional Composition, and Functional Characterization of Selenium-Rich Skipjack Tuna (Katsuwonus pelamis) Nuggets: An Exploratory Dietary Evaluation of Cardiometabolic Outcomes, Physical Activity, and Screen Time

Nutrient-dense seafood products may provide a practical food-based strategy for improving dietary quality while delivering selenium, high-quality protein, omega-3 fatty acids, and other beneficial nutrients. This study developed and characterized selenium-rich skipjack tuna ( Katsuwonus pelamis ) nuggets and explored their nutritional functionality, sensory acceptability, and short-term associations with cardiometabolic and lifestyle-related outcomes. The nuggets underwent nutritional, physicochemical, antioxidant, microbiological, and sensory characterization and were subsequently evaluated in a 12-week randomized dietary intervention involving 120 adults with ischemic cardiomyopathy, allocated to receive 100 g/day of tuna nuggets (n = 60) or standard dietary counseling (n = 60). Anthropometric, metabolic, inflammatory, physical-activity, sedentary-behavior, and screen-time measures were assessed at baseline and week 12. The nuggets provided 31.93 g protein, 1.75 g fat, 2.3 g dietary fiber, 35.0 µg selenium, and 0.82 g omega-3 fatty acids per 100 g, with satisfactory microbiological quality and high sensory acceptability. After 12 weeks, the intervention group showed greater improvements than controls in body weight, BMI, fasting glucose, total cholesterol, LDL-C, HDL-C, triglycerides, and hs-CRP (all between-group p < 0.05). Physical activity increased, whereas sedentary and screen time decreased. Exploratory mediation analyses identified significant indirect associations involving selenium, protein, omega-3 fatty acids, dietary fiber, and total antioxidant capacity, although these findings do not establish causal mechanisms. Overall, selenium-rich skipjack tuna nuggets showed favorable nutritional and sensory characteristics, and their consumption was associated with favorable changes in selected cardiometabolic biomarkers and lifestyle-related behaviors. However, these findings cannot be attributed specifically to selenium or any individual food component and require confirmation in larger, longer-term randomized controlled trials.