Effects of Soy Protein and Creatine Supplementation on Body Composition, Acute Muscle Injury, and Biochemical Parameters in Trained Men Performing Resistance Exercise

This study was designed as a randomized controlled trial. The study will be conducted with 54 male participants aged 18-35 years (CrM: 18, Soy: 18, Placebo: 18) who regularly attend gyms located in the Central district of Bitlis province and apply to the laboratory of Bitlis State Hospital. Data collection is planned between December 2025 and February 2026. Inclusion criteria for the study were determined as being between 18 and 35 years of age, engaging in regular resistance training for at least one year, having no metabolic diseases, not using regular medication, and not having used any dietary supplements in the last three months prior to the study. Exclusion criteria were defined as being under 18 or over 35 years of age, engaging in resistance exercise for less than one year, using tobacco and alcohol, using regular medication, having an allergy to soy protein, having a psychiatric disorder, and being female.

Voluntary individuals evaluated according to the inclusion criteria and deemed suitable for participation will be randomized using the 'Block Randomization' method. One-third of the individuals selected through the randomization method will be given creatine monohydrate supplementation, one-third soy protein supplementation, and one-third placebo. While all products to be used in our study are provided by a company with GMP (Good Manufacturing Practices) certification, products commonly consumed by athletes will be used, as stated in the literature summary. Creatine and soy protein are products that are widely used as dietary supplements in the market and are accepted as safe. Both products will be used within recommended dose limits. No invasive procedures will be performed on the participants in our study (no blood sampling will be conducted); participants who are routinely checked by a specialist physician will be included in the study.

A Personal Information Form, prepared by the researchers through a literature review, will be administered to the participating individuals using the face-to-face interview technique. The Personal Information Form questions consist of 15 open-ended and multiple-choice questions aimed at determining the individuals' general information, dietary habits, dietary supplement use, and nutrition and hydration status during training.

To evaluate the nutritional status of the participants, a consecutive three-day (two weekdays and one weekend day) dietary intake record will be taken at the beginning and end of the study. A three-day Food Record Form will be given to the participants during the first and fourth visits, and how to complete it will be explained to the individuals. After the records are collected, the amounts and contents of the consumed foods will be detailed and questioned by the participants and the researcher. In the evaluation of foods consumed at home, the book 'Food and Nutrition Photo Catalogue: Measures and Amounts' will be utilized. The portion contents of meals consumed by individuals outside the home will be calculated using the book 'Standard Food Recipes for Institutions Serving Mass Catering'. Dietary intake records will be analyzed using the BeBIS Nutrition Information System (Germany) 7.2 software, and the daily average energy and macro/micronutrient amounts consumed by the individuals will be determined.

Biochemical parameters to be used in the study will be obtained from the individuals' files within the scope of routine analyses performed during routine applications to Bitlis State Hospital. Hemogram values, creatine kinase, fasting blood glucose, total cholesterol, triglyceride, HDL cholesterol, LDL cholesterol, AST, ALT, ALP, iron, ferritin, and testosterone values of all individuals participating in the study will be used.