Nowadays, many persons who exercise consume dietary supplements. Previous scientific studies have found that protein supplementation increases muscle mass when combined with an exercise program. In addition, vitamin D probably improves performance and muscle function. Likewise, ω3 fatty acids, apart from improving cardiovascular function, may also increase protein synthesis and performance. Thus, the aim of this study is to investigate the efficacy of a novel aquaculture-based sport supplement of proteins, ω3 fatty acids and vitamin D on physical performance, body composition, and the biochemical profile of persons following high-intensity functional training (HIFT). The efficacy of the experimental supplement (E) will be compared with whey protein (W) and maltodextrin (a carbohydrate) as placebo (P).

Thirty healthy trained individuals (15 male and 15 female), aged 18-35, will take E, W, and P during three 6-week periods of HIFT (a different supplement each period) with three workouts a week and a washout (no supplement) period of 2 weeks between supplementation periods. E is a combination of powder, containing protein and vitamin D, and capsules containing ω3 fatty acids. When on E, participants will receive 0.6 g protein/kg body weight, 20 μg vitamin D, and 1.8 g ω3 fatty acids daily. When on W, they will receive 0.6 g protein/kg body weight and, when on P, they will receive 0.6 g maltodextrin/kg body weight daily. The order of E, W, and P will be random and counterbalanced. Throughout the study, participants will be on isoenergetic nutritional plans to avoid differences in energy intake that might compromise the validity of the study. The dietary plans will be individualized and will provided 1.0 g protein/kg body weight/day.

Participants will undergo measurements of muscle strength, muscle endurance, aerobic capacity, and body composition prior to the first supplementation period, between periods, and after the third period. Also, blood amino acids, fatty acid acids, vitamin D, hematology, biochemistry, and hormones will be measured. To avoid bias, assessors will not know which supplement each participant is taking during each period.

The main hypotheses of the study are: 1) Consumption of E will increase lean body mass compared to W and P; 2) consumption of E will improve muscle strength, muscle endurance, and aerobic capacity compared to W and P; and 3) consumption of E will result in a better blood amino acid, fatty acid, and vitamin D profile.

Inclusion Criteria:

• Regular training (mixed endurance and resistance training 3-6 times a week, 50 min each session, for the past 4-6 months) as assessed by gym records or questionnaires.
• Clearance from a pathologist or cardiologist to perform maximal exercise.
• Mixed isoenergetic diet for the past 4-6 months.

Exclusion Criteria:

• Smoking (even one cigarette or nicotine-containing device over the past 6 months).
• Any injuries to the musculoskeletal system that could interfere with the execution of training.
• Chronic disease.
• Fish or oyster allergy.
• Milk allergy.
• Pregnancy, lactation or planning a pregnancy within the duration of the study.
• Regular use of prescription medicine or supplements that might affect muscle function or recovery over the past month.
• Intermittent or religious fasting.
• Any vegetarian, ketogenic and protein diet.

Participants are instructed not to disclose the supplement they are taking to their trainers, investigators, or outcome assessors.