## 4 Discussion
### Daily Coverage of Mineral Requirements After Consumption of Infant Formulas and Human Milk  
Based on the recommended intake values of IFs on the labels and the recommended daily intake values of HM obtained from the recommendations of the Polish Society for Paediatrics Gastroenterology, Hepatology and Nutrition [26], the total daily mineral intake of infants was calculated and compared to the Polish reference intake values. The present study verified whether the intake of IF and breast milk would exceed the values set by the standards. Comparing the whole-day intake values of minerals from individual IFs with the reference values recommended by specific standards [27; 28], it was identified that all types of initial IFs and special IFs (except S4) exceeded the contents of tested minerals. [PERSON] et al. [3] indicated that initial IFs contained higher amounts of Ca, Mg, Na, P, Fe, Zn, Cu, and Mn than those specified by standards. IFs can have up to six times higher levels of Ca than in breast milk. Although the bioavailability of Ca from IFs is significantly lower, there is a risk of exceeding the daily intake of this element. Consequently, this can impair the absorption of other minerals--Mg, Fe, and Zn [49]. Considering the lower bioavailability of Ca from IFs, EFSA recommends a Ca intake of 700 mg per day, considering infants up to 6 months of age [33]. [PERSON] et al. [3] report that Zn concentrations in IFs (initial and follow-on) exceeded the upper level (UL) values (4 and 5 mg/day for infants 0-6 and 7-12 months). On the other hand, our study reported that only Ca, P (except C-D2), Zn, and Cu were exceeded after a full daily intake of follow-on IFs. In both our study and that of [PERSON] et al. [3], it was observed that in all follow-on formulas, the content of Mn and Na was lower than that specified by the norms of nutrition for the Polish population [27; 28]. While initial IFs are sufficient to meet an infant's whole-day mineral needs, follow-on formulas introduced after 6 months of age may be deficient in selected macro- and microminerals. It must be considered that after 6 months of age, solid foods are introduced to infants as a dietary supplement to essential nutrients [59]. Therefore, even if the whole-day intake of selected follow-on IFs does not cover the need for selected minerals, it should be considered that infants in this age group also receive minerals from other food sources [3]. Our study reported the highest estimated coverage of Fe requirements, which in initial and specialist IFs (except S4) reached up to 25 times the value set by nutrition standards for the Polish population [27; 28]. For follow-on IFs, the values ranged from 27 to 60%. The differences in the realization of the daily requirement for Fe between initial and follow-on IFs are attributable to differences in standards for this nutrient for infants relative to age. While the Fe requirement for infants aged 7-11 months was 11 mg/day, it was 0.3 mg/day for infants up to six months [Table S3]. Fe content in IFs ranges as high as 8-14 mg/L. Due to concerns about the low bioavailability of Fe and the risk of deficiency among infants, IFs contain significantly higher contents of this element [60]. [PERSON] et al. [60] reduced the Fe content of IFs from 8 to 2 mg/L and provided such a mixture to infants to control serum Fe levels. The authors' results indicate that reducing Fe in IF to 2 mg/L does not significantly affect the incidence of Fe deficiency. [PERSON] et al. [61] indicate that the Fe content of IFs can cover the daily Fe requirement by 947%, even though the Fe content is within the range of regulatory standards. Excess Fe, like deficiency, can have negative effects on the infant's body, including those related to impaired absorption of other minerals and pro-oxidant effects [62]. It is reasonable to add higher amounts of minerals to IFs due to their much lower bioavailability compared to HM [3].