## 4 Discussion
### Mineral Content of Infant Formulas
#### 4.1.2 Specialist Infant Formulas  
Until now, there have been only a few studies available on the mineral content of specialist IFs. The most common type of specialist IF is the lactose-free formula used when there is frequent diarrhea in the child. These formulas do not contain lactose in the composition, and the main carbohydrate source is maltodextrin [35]. [PERSON] [35] reports that the Fe content in this type of IF is reduced to inhibit the growth of pathogenic intestinal bacteria. In addition, these formulas contain more electrolytes (Na, K) to prevent dehydration caused by diarrhea. Among the specialist IFs that contained partially hydrolyzed cow's milk protein in the formulation (S1, S2), formula S1, intended for gastrointestinal disorders, contained the highest Na and K content. On the other hand, it should be noted that excessive Na intake in IF) can lead to blood pressure problems in infancy and later in adolescence [36]. Conversely, excess K can result in hyperkalemia [37]. Furthermore, excessive sodium intake during infancy can impair sodium metabolism and potentially cause kidney damage [38]. Soy-based formulas are designed for infants who are intolerant to milk protein or have galactosemia or lactose digestion problems [39]. As in formulas designed for lactose intolerance, the carbohydrate source is maltodextrin. However, unlike these formulas, in IFs based on soy protein, the Fe content is not reduced, and thus, the risk of Fe deficiency is lower [35]. Soy-based IFs contain about 1.5% phytates, which can impair mineral absorption. IFs produced today based on soy protein are reported to contain P and Ca in concentrations about 20% higher than conventional IFs. Formula S3, based on soy protein, contained about 47 and 30% more Ca and P than conventional initial IFs and 20 and 17% more compared to follow-on IFs [40]. It should be emphasized that phytic phosphorus found in plant materials (including soybeans) is not well digested and has a lower bioavailability than that derived from milk [33; 41]. This is also the reason that soy-based IF can be supplemented with higher amounts of P. In a study by [PERSON] et al. [33], soy-based formula had the lowest bioavailability of Fe and Zn. The presence of certain anti-nutritional substances in soy, such as phytates and phenols, can lead to the formation of insoluble complexes that precipitate during intestinal digestion, reducing the absorption of Fe and Zn. Therefore, soy-based formulas are often additionally enriched with these elements to ensure that their levels do not deviate from the norm [35]. In our study, the Fe and Zn content of the S3 formula did not differ from that of the other IFs (it was the same as or lower than that of the other IFs). Another popular type of specialist formula is protein hydrolysates, designed for infants who cannot digest milk proteins or have severe lactose intolerance. Such formulas are easily digestible and have low antigenicity due to the use of milk protein hydrolysis. To produce formulas based on protein hydrolysates, partial or extensive hydrolysis is used [35]. Of the IFs tested, two IFs with a moderate degree of hydrolysis (S1, S2) and one with a high degree of hydrolysis (S4) were evaluated. Of these formulas, IF S1 had a higher Ca and Mg content relative to S2 and S4. In contrast, the S4 formula had a higher Fe content than the other two discussed. In addition, both S1 and S4 were characterized by higher K content than S2. In severe hypersensitivity to milk proteins or the infant's unacceptability of formulas based on milk protein hydrolysates, amino acid mixtures based on synthetic free amino acids are used [42]. In the study presented here, two IFs based on free amino acids (S5 and S6) were analyzed. The S6 formula stood out from other specialist IFs in terms of Na and K content. Due to the limited amount of research considering the literature on specialist IFs in terms of their chemical composition, including mineral content, the discussion in this area is limited.