Metabolic balance studies: A comprehensive protocol and methodological approach for assessing intestinal function.

Adequate absorption of nutrients, fluids, and electrolytes is essential for maintaining physiological function and overall health. Clinical evaluation of the intestinal absorptive capacity is therefore important for diagnosing and managing chronic gastrointestinal disorders with impaired nutrient absorption. To this end, metabolic balance studies (MBS), which assess the intestinal absorption of energy, macronutrients, fluids and electrolytes, are considered the gold standard. However, full MBS are performed in only a few specialized centers due to their complexity and high resource demands. This paper provides a detailed methodological practice guide to conducting MBS, covering the entire process from standardized sample collection to laboratory procedures such as homogenization and freeze-drying, followed by quantitative analysis of energy, fat, carbohydrates, protein (nitrogen content), wet weight, and electrolytes. By offering a clear and reproducible framework, the aim of this guide is to support the broader implementation of MBS as an objective tool for assessing digestive and absorptive capacity in patients with malabsorption.