Functional Properties of Enriched Curd with Collagen and Plant Phytochemicals for Athletes and Physiological Benefits: Evidence Data from Preclinical Trials In Vivo

<b>Background/Objectives</b>: The aim of this study was to establish the multifactorial physiological effect of a functional curd product enriched with collagen-containing concentrate and phytochemical extracts of various natures, under conditions of in vivo experiment. <b>Methods</b>: Biomarkers, such as antioxidant activity (glutathione peroxidase, glutathione reductase, MDA), immune response (IgA, IgG, IgM, IL-6, TNF-α), and purine metabolism (uric acid, xanthine oxidase, 5'-nucleotidase) were selected for evaluation and their influence change. The model was white outbred rats (<i>n</i> = 45), randomly distributed into three groups: control (basic product), experimental group 1 (supplements of collagen-containing concentrate and extract of the composition of sea buckthorn and rosehips), and experimental group 2 (supplements of collagen-containing concentrate and extract of the composition of yarrow and sage). <b>Results</b>: In both experimental groups, a reliable increase in the enzymatic activity of the antioxidant system, a decrease in lipid peroxidation and the level of proinflammatory cytokines, an increase in immunoglobulins, and activation of 5'-nucleotidase were observed. The most pronounced effects were observed with the introduction of a curd product containing collagen-containing concentrate and sea buckthorn and rosehip extract. <b>Conclusions</b>: The scientific novelty of the study lies in the first comprehensive in vivo evaluation of the combined enrichment of a dairy product with collagen and plant extracts for a set of biomarkers. The data obtained confirm the physiological activity and functional properties of the developed product, which can be considered as a promising means of specialized and sports nutrition with proven biological action.