**Background:** Picky eating affects up to 62% of preschool children and can lead to inadequate intake of calories and micronutrients, potentially impairing growth. While nutritional guidance is standard, the additional benefit of oral nutritional supplementation in eutrophic picky eaters remains unclear. This study aimed to determine whether supplementation provides added benefit over guidance alone in improving anthropometric outcomes, nutrient intake, appetite, and health complications.
**Methods:** This was a randomized, single-blind, controlled clinical trial conducted from January 2021 to August 2022 in a private pediatric clinic in Ribeirão Preto, Brazil. Children aged 24–60 months with picky eating and BMI z-score between −2 and +2 were eligible. Of 46 referred children, 43 were eligible; 2 were excluded (cow's milk allergy, lactose intolerance, chronic diseases), and 6 withdrew, leaving 35 participants (17 control, 18 intervention). Randomization was computer-generated (1:1 ratio) with allocation concealment via REDCap. The control group received nutritional guidance over 7 meetings (180 days). The intervention group received identical guidance plus 200 mL of a complete oral supplement (Milnutri Complete®, 1 kcal/mL) twice daily for 180 days. Primary outcomes were weight, height, and BMI z-scores (WHO curves) and body fat percentage (BFP) via bioimpedanciometry (InBody 270). Secondary outcomes included energy and nutrient intake (24h recall at T0, T3, T6) assessed against DRI EAR/AI. Tertiary outcomes included appetite, physical activity, and global health scales (1–10, parent-reported, not validated) and health complications. Statistical analysis used linear mixed-effects models (lme4 in R) with time × group interaction; Poisson models for count data. Significance level was 5%.
**Key Results:** At baseline, groups were similar except for appetite scale score (control 7.29 vs. intervention 5.06, p < 0.01). Supplement adherence was 100%; mean intake was >80% of prescribed dose through T5, dropping to 76.9% at T6. There were no significant time × group interactions for weight z-score (p = 0.422), height z-score (p = 0.178), BMI z-score (p = 0.648), or BFP (p = 0.496). However, within the intervention group, weight and height z-scores increased significantly from T0 to T6 (p < 0.05), while BMI z-score and BFP remained unchanged. The control group showed no significant anthropometric changes. For nutrient intake, the intervention group had significantly higher intakes at T3 and T6 of iron (T6: 11.3 vs. 6.4 mg/day, p = 0.002), zinc (T3: 9.3 vs. 5.3 mg/day, p = 0.017), vitamin D (T6: 10.5 vs. 4.6 mcg/day, p = 0.001), vitamin C (T6: 119.6 vs. 43.8 mg/day, p = 0.002), vitamin B12 (T6: 4.3 vs. 2.6 mcg/day, p = 0.023), and folate (T6: 115.3 vs. 67.1 mcg/day, p = 0.008). Inadequacy rates for vitamin D dropped from 83.3% to 27.8% in the intervention group, and for folate from 77.8% to 61.1%. The intervention group showed a significant increase in appetite scale score from T0 to T6 (p < 0.05), while the control group did not. Health complications increased significantly in the control group over time (T0 vs. T6) but not in the intervention group. No significant between-group differences were found for physical activity or global health scales.
**Clinical Implications:** This study provides evidence that six months of oral nutritional supplementation in eutrophic picky eating children can support linear growth (height gain) and weight gain without increasing BMI or body fat percentage, indicating proportional growth rather than fat accumulation. Supplementation also corrected several common micronutrient deficiencies (iron, zinc, vitamins C, D, B12, folate) and was associated with improved appetite. The high adherence (>80%) suggests the supplement was well-accepted. These findings support the use of complete oral supplements as an adjunct to nutritional guidance in picky eaters, particularly when micronutrient deficiencies or growth faltering are concerns. Limitations include small sample size (n = 35), use of non-validated scales, and potential recall bias. Larger, longer-term studies are needed to confirm these findings and assess effects on physical activity, global health, and infection rates.