Functional poor appetite is common in young children and may be linked to suboptimal micronutrient intake and feeding behavior. This study evaluates whether a zinc-containing oral supplement (Biolizin syrup) can improve eating behavior in children aged 6 to 36 months who have poor appetite without an identifiable medical cause. Participants are followed for 42 days with clinic visits at Day 0, Day 7, Day 21, and Day 42. Caregivers complete validated questionnaires about feeding difficulties and eating behavior; the child's weight and length/height are measured at each visit. Safety is assessed through review of adverse events and routine laboratory tests; serum zinc may be measured according to the protocol. The primary outcome is the change from baseline to Day 42 in the total score of a validated feeding-difficulty scale. Secondary outcomes include changes in Children's Eating Behaviour Questionnaire (CEBQ) subscales, WHO growth indices, serum zinc (if measured), and overall safety

Poor appetite in toddlers often reflects a combination of nutritional and behavioral factors. Zinc is an essential trace element that contributes to taste perception, mucosal integrity, and appetite regulation; suboptimal zinc status may exacerbate reduced intake and feeding problems. Biolizin is an oral zinc-containing supplement intended to support appetite and healthy feeding behavior in young children. The study aims to determine whether the supplement, provided together with standardized caregiver counseling on responsive feeding practices, improves caregiver-reported feeding difficulty and eating behavior over 42 days. After consent and screening, eligible children attend visits at Day 0, Day 7 (±2), Day 21 (±3), and Day 42 (±4). At each visit, clinicians review medical history and concomitant treatments, record anthropometrics, and caregivers complete a validated Vietnamese feeding-difficulty scale (0-24, higher scores indicate worse difficulty) and the CEBQ subscales. The study product is taken orally per age-based dosing specified in the protocol; adherence is checked using dosing diaries and returned bottle counts where applicable. Safety laboratories (e.g., complete blood count, liver and renal chemistry) are planned at baseline and Day 42; serum zinc may be obtained according to protocol. Adverse events are collected from consent through Day 42 and are managed according to clinical judgment; expected reactions are generally mild (for example, gastrointestinal discomfort, taste changes, or rash). Source data are recorded in case report forms and entered into a secure database with audit trails, and only de-identified data are used for analysis or sharing. The study has ethics approval and written informed consent is obtained from caregivers before any procedures.

Inclusion Criteria:

• Age 6 to 36 months at screening.

• Functional poor appetite for ≥2 weeks with at least one of the following:

  • Clearly reduced intake versus usual (lower amount of food and/or fewer meals per day);
  • Prolonged meal duration (>30 minutes per meal);
  • Refusal or avoidance of familiar foods previously accepted;
  • Oppositional feeding behaviors (turning away, crying, gagging/retching, prolonged food holding, lack of cooperation during meals).

• No obvious organic cause of poor appetite (e.g., acute infection, gastrointestinal/metabolic disease).

• Weight not below -2 SD compared with WHO growth standards.

• Parent/guardian provides written informed consent.

Exclusion Criteria:

• Ongoing acute or chronic illnesses that can affect intake or absorption, including but not limited to:

  • Acute infections (e.g., tonsillitis, pneumonia, otitis media, viral febrile illness, acute diarrhea);
  • Chronic conditions affecting digestion or metabolism (e.g., celiac disease, malabsorption syndromes, chronic liver disease, chronic kidney disease, diabetes).

• Neurodevelopmental or neurological conditions that impair feeding (e.g., cerebral palsy, autism spectrum disorder, global developmental delay).

• Current or recent use of medications known to alter appetite or digestion/absorption (e.g., systemic corticosteroids, antiepileptics, prolonged antibiotics).

• Use of zinc-containing products or other appetite stimulants within 7 days before screening.

• Known hypersensitivity to any component of the study product.

• Malabsorption, severe malnutrition, or requirement for specialized nutrition, including:

  • Confirmed or suspected malabsorption (e.g., celiac disease, severe lactose intolerance, short bowel syndrome, inflammatory bowel disease);
  • Severe malnutrition per WHO criteria (e.g., weight-for-length Z-score < -3 SD, nutritional edema, marked loss of subcutaneous fat/muscle);
  • Physician-prescribed specialized nutrition plans (therapeutic formulas for cow's milk protein allergy, severe malnutrition, tube feeding, or individualized nutrition regimens beyond usual diet).

• Nonadherent caregiver or high risk of loss to follow-up as judged by the investigator.

De-identified individual participant data (IPD) underlying the primary and secondary outcomes will be shared, including: baseline demographics/clinical characteristics; CEBQ item- and subscale-level scores and the prespecified composite; Hoang Thi Bach Yen anorexia scale scores; anthropometrics and WHO Z-scores; serum zinc and laboratory safety values; adverse events; concomitant medications; intervention assignment and adherence. A data dictionary/codebook will accompany the dataset. Direct identifiers will be removed and indirect identifiers minimized per protocol and institutional policy.

IPD and supporting documents will be available beginning ~6-12 months after publication of the primary results and for 36 months thereafter. If no publication occurs, availability will begin within 24 months after last patient last visit and continue for 36 months.

Qualified researchers from academic, non-profit, or health-care institutions may request access by submitting a methodologically sound proposal and analysis plan to the Sponsor/PI (see Contacts). Requests require IRB/ethics determination or waiver and a signed Data Use Agreement. Upon approval, de-identified data and documents will be provided via secure, access-controlled repository or encrypted file transfer. Re-identification attempts and onward sharing are prohibited; use is limited to the approved objectives.

Not applicable (open-label)