###### Abstract  
In recent years, the scientific community has made significant progress in understanding nutrition, leading consumers to shift their preferences away from animal-based protein products and towards natural, plant-based protein sources. This study aimed to determine the nutritional value, in vitro cytotoxicity and antioxidant activity for different sources of high protein content products (pea, yeast, almond, spirulina and _Pleurotus_ spp.) with potential usage as raw materials for dietary supplements, especially since these products do not benefit from stricter regulation requirements regarding their actual health benefits. The characterization of raw materials consisted in evaluation of their nutritional profile (by addressing moisture content, crude protein content, extractable fat, ash, carbohydrates) and microbial contamination (TAMC, TYMC, _Enterobacteriaceae_ and \(\beta\)-glucuronidase positive _Escherichia coli_), total content of free amino acids, soluble proteins, phenols and flavonoids, as well as antioxidant activity through chemical assays. We used 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazol-dium bromide (MTT) assay and lactate dehydrogenase (LDH) release to evaluate the potential cytotoxicity of selected raw materials. Results obtained indicate high percentages of proteins for the pea powder (77.96%) and _Spirulina_ powder (64.79%), _Pleurotus_ spp. flour had strong antioxidant activity, while the highest contamination values were registered for _Pleurotus_ spp. powder (4.6 \(\times\) 10\({}^{5}\) CFU/g or 5.66 log CFU/g). Cytotoxicity results demonstrate that tested ingredients have an impact on the metabolic activity of cells, affecting cellular integrity and provoking leakage of DNA at several concentrations. While plant-based protein supplementation may appear to be a promising solution to balance our busy lives, there are several advantages and disadvantages associated with them, including issues related to their absorption rate, bioavailability, cytotoxicity and actual nutritional benefits. high protein ingredients; cytotoxicity; antioxidant activity; nutritional value; dietary supplements +
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This shift can be attributed to several factors, including a growing interest in healthy living and wellness, as well as an increased awareness of the importance of proper nutrition for overall health and well-being. Additionally, advancements in nutritional science have led to a better understanding of the role that proteins play in the body and the potential benefits of protein supplementation for various health goals. Overall, this shift towards protein supplementation and dietary supplementation, in general, is indicative of a larger trend towards a greater focus on nutrition and wellness in modern society [2]. Therefore, proteins, being essential macronutrients, play a crucial role in the growth and maintenance of the human body as they provide energy, amino acids, and possess various physiochemical and sensory properties, making them useful functional ingredients for promoting health [3]. Despite their importance, protein deficiency remains a major concern. Furthermore, increased protein intake has been associated with several health benefits due to its fundamental role in all body cells and maintenance of the immune system. Notably, higher protein consumption has been linked to increased muscle mass and endurance [4; 5; 6; 7].The origin of protein can have a significant impact on the health benefits it provides. Proteins from animal sources, such as meat, dairy and eggs tend to be high in saturated fat and cholesterol, which can increase the risk of heart disease and other chronic health conditions when consumed in excess [4; 5]. On the other hand, proteins from plant sources, such as legumes, nuts, seeds, and whole grains tend to be lower in saturated fat and cholesterol, and higher in fiber, vitamins, minerals, and antioxidants, which have been linked to a reduced risk of chronic diseases [6; 7].