Zinc Supplementation Significantly Increases Growth Hormone Factors in Non-Zinc-Deficient Children, Gold Standard Study Finds

A 2015 triple-blind randomized controlled trial published in the Journal of the American College of Nutrition demonstrated that oral zinc supplementation at 10mg/day for 3 months significantly increased plasma IGF-1 and IGFBP-3 concentrations in healthy, non-zinc-deficient children — suggesting zinc plays an active role in the GH-IGF-1 axis independent of baseline zinc status.

Study Design

Rocha et al. enrolled 40 prepubertal schoolchildren (23 male, 17 female, aged 8-9 years) in a triple-blind, placebo-controlled, randomized trial. Subjects were divided into an experimental group (n=20, receiving 10mg elemental zinc daily) and a control group (n=20, receiving 10% sorbitol placebo) over a 3-month intervention period. All participants were confirmed non-zinc-deficient and eutrophic at baseline. Anthropometric measurements, dietary assessments, and blood biomarkers were collected pre- and post-intervention.

The triple-blind methodology — in which subjects, caregivers, and investigators were all blinded to group allocation — represents the highest standard of bias control in clinical trial design.

Results

Oral zinc supplementation in the experimental group produced the following statistically significant outcomes:

The IGFBP-3 result (p < 0.0001) is particularly notable, indicating an extremely low probability that the observed increase was attributable to chance.

Biological Significance

IGF-1 (Insulin-like Growth Factor 1) is the primary mediator of growth hormone action at the growth plate. Secreted by the liver in response to circulating GH, IGF-1 stimulates chondrocyte proliferation and differentiation in the epiphyseal growth plate, directly driving longitudinal bone growth.

IGFBP-3 (Insulin-like Growth Factor Binding Protein 3) functions as the principal carrier protein for circulating IGF-1, extending its plasma half-life and regulating bioavailability at target tissues. Elevated IGFBP-3 concentrations increase the proportion of IGF-1 that survives hepatic clearance and reaches the growth plate in bioactive form.

The concurrent increase in osteocalcin — a bone-specific protein responsible for calcium deposition into the bone matrix — indicates that zinc supplementation may support bone mineralisation pathways in parallel with the GH-IGF-1 axis.

Context Within Existing Literature

These findings are consistent with prior work by the same research group. Alves et al. (2012), published in the Journal of Pediatric Endocrinology and Metabolism, reported that oral zinc supplementation at 5mg/day in 30 eutrophic children aged 6-9 produced increases in IGF-1 and IGFBP-3, with a positive correlation between GH and zinc area under the curve. The authors concluded that zinc was "effective in improving secretory levels of IGF1 and IGFBP3, GH potentialization, and height."

A separate systematic review and meta-analysis on zinc and IGF-1 in humans confirmed that zinc supplementation elevates IGF-1 in both zinc-deficient and non-zinc-deficient populations, suggesting that the relationship between zinc and the somatotropic axis is not solely a function of deficiency correction.

An Egyptian study (Cesur et al., 2009) examining 50 prepubertal short-stature children with zinc deficiency reported significant increases in height standard deviation score (p = 0.033), IGF-1 (p < 0.01), and IGFBP-3 (p = 0.042) following 3 months of zinc supplementation.

Clinical Implications

The Rocha et al. findings are notable because the study population comprised healthy, non-deficient children — a cohort typically excluded from micronutrient intervention research. The demonstration that 10mg/day of oral zinc produces measurable upregulation of the GH-IGF-1 axis in this population suggests that zinc may have an optimisation function beyond deficiency correction, with potential applications in paediatric growth support for children within normal nutritional parameters but below expected growth trajectories.

The 10mg daily dose used in the trial falls within established safe intake ranges for children aged 8+ (tolerable upper intake level: 23mg/day for ages 9-13 per IOM guidelines) and is readily achievable through supplementation.