Micronutrient Intake during Complementary Feeding in Very Low Birth Weight Infants Comparing Early and Late Introduction of Solid Foods: A Secondary Outcome Analysis

Abstract

Background/Objectives: The complementary feeding period is crucial for addressing micronutrient imbalances, particularly in very low birth weight (VLBW) infants. However, the impact of the timing of solid food introduction on micronutrient intake in a representative VLBW population remains unclear. Methods: This prospective, observational study investigated micronutrient intake during complementary feeding in VLBW infants categorized based on whether solids were introduced early (<17 weeks corrected age (CA)) or late (≥17 weeks CA). Nutritional intake was assessed using a 24 h recall at 6 weeks CA and with 3-day dietary records at 12 weeks and at 6, 9, and 12 months CA. Results: Among 218 infants, 115 were assigned to the early group and 82 to the late group. In total, 114-170 dietary records were valid for the final analysis at each timepoint. The timepoint of solid introduction did not affect micronutrient intake, except for a higher iron and phosphorus intake at 6 months CA in the early group (early vs. late: iron 0.71 vs. 0.58 mg/kg/d, adjusted p-value (p-adj.) = 0.04; phosphorus 341 vs. 286 mg/d, p-adj. = 0.04). Total vitamin D, calcium, zinc, and phosphorus greatly met intake recommendations; however, dietary iron intake was insufficient to equalize the iron quantity from supplements during the second half year CA. While nutrient intakes were similar between infants with and without comorbidities, breastfed infants had lower micronutrient intakes compared with formula-fed infants. Conclusions: This study suggests that micronutrient intakes were sufficient during complementary feeding in VLBW infants. However, prolonged iron supplementation may be necessary beyond the introduction of iron-rich solids. Further research is essential to determine micronutrient requirements for infants with comorbidities.

Keywords: calcium; complementary feeding; iron; micronutrient intake; phosphorus; preterm infants; vitamin D; zinc.

Figure 1

Dietary and total iron intake (mg/kg/d). Data are presented as the estimated marginal mean and standard error. Significant differences (adjusted p-value < 0.05) are marked with *. The red dotted lines represent the recommended iron supplementation (2–3 mg/kg/d until 6–12 months) in preterm infants. Total = dietary intake + supplementation. (A) Dietary iron intake (mg/kg/d) comparing an early vs late introduction of solid foods. (B) Total iron intake (mg/kg/d) comparing an early vs late introduction of solid foods.

Figure 2

Dietary and total vitamin D intake (IU/d). Data are presented as the estimated marginal mean and standard error. The red dotted lines represent the recommended vitamin intake (800 IU/d) in preterm infants. Total = dietary intake + supplementation. (A) Dietary vitamin D intake (IU/d) comparing an early vs late introduction of solid foods. (B) Total vitamin D intake (IU/d) comparing an early vs late introduction of solid foods.

Figure 3

Dietary calcium and phosphorus intake (mg/d). Data are presented as the estimated marginal mean and standard error. The red dotted lines represent the recommended intake of (A) calcium (0–3 months: 220 mg/d, 4–12 months: 330 mg/d) and (B) phosphorus (0–3 months: 120 mg/day, 4–12 months: 180 mg/day) for term infants. Significant differences (adjusted p-value < 0.05) are marked with *.

Figure 4

Micronutrient intakes in infants with and without comorbidities (BPD, NEC, IVH). Data are presented as the mean and standard error. Significant differences (adjusted p-value < 0.05) are marked with *. The red dotted lines represent the recommended dietary and supplemental intakes of the respective micronutrients. Total = dietary intake + supplementation. (A) Total Iron Intake (mg/kg/d) in infants with and without comorbidities. (B) Total vitamin D Intake (IU/d) in infants with and without comorbidities. (C) Dietary Calcium Intake (mg/d) in infants with and without comorbidities. (D) Dietary Phosphorus Intake (mg/d) in infants with and without comorbidities. (E) Dietary Zinc Intake (mg/d) in infants with and without comorbidities.

Figure 5

Micronutrients in breastfed, formula-fed, and mixed-fed infants. Data are presented as the mean and standard error. Statistical testing was performed comparing breastfed vs. formula-fed and breastfed vs. mixed-fed. Significant differences (adjusted p-value < 0.05) are marked with *. The red dotted lines represent the recommended dietary and supplemental intakes of the respective micronutrients. Total = dietary intake + supplementation. (A) Dietary iron intake (mg/kg/d) in breastfed, formula-fed and mixed-fed infants. (B) Total iron intake (mg/kg/d) in breastfed, formula-fed and mixed-fed infants. (C) Dietary vitamin D intake (IU/d) in breastfed, formula-fed and mixed-fed infants. (D) Total vitamin D intake (IU/d) in breastfed, formula-fed and mixed-fed infants. (E) Dietary calcium intake (mg/d) in breastfed, formula-fed and mixed-fed infants. (F) Dietary phosphorus intake (mg/d) in breastfed, formula-fed and mixed-fed infants. (G) Dietary zinc intake (mg/d) in breastfed, formula-fed and mixed-fed infants.