Assessment of zinc inadequacy among tribal adolescent population of central India - A cross-sectional study

**Background:** Zinc is an essential micronutrient for growth and sexual maturation during adolescence. Tribal adolescents in India may be at elevated risk of zinc deficiency due to plant-based diets with poor zinc bioavailability. This study aimed to evaluate the risk of zinc deficiency among adolescents of the Gond, Bhil, and Korku tribes in Madhya Pradesh by estimating the prevalence of inadequate zinc intake, low serum zinc, and stunting.

**Methods:** A community-based cross-sectional survey was conducted in three purposively selected districts of Madhya Pradesh where the Bhil (Jhabua), Korku (Betul), and Gond (Mandla) tribes constitute >90% of the population. Data collection occurred from December 2015 to April 2016 (Mandla), May to August 2016 (Betul), and October 2017 to February 2018 (Jhabua). A total of 2,310 households were approached; 2,224 households with 5,151 adolescents participated. Dietary recall data were obtained from 4,673 adolescents (90.7% response rate), anthropometry was conducted on 2,437 participants, and serum zinc was analyzed in 844 adolescents. Dietary intake was assessed using a 24-hour recall method with weighing of raw ingredients. Usual zinc intake was estimated using the National Cancer Institute one-day method with external variance ratios. Serum zinc was measured by atomic absorption spectrophotometry. Stunting was defined as height-for-age Z-score <−2SD using WHO standards.

**Key Results:** The overall prevalence of dietary zinc inadequacy was 42.6% (95% CI: 41.2–44.1) using IZiNCG estimated average requirements (EAR) and 64.8% (95% CI: 63.4–66.2) using ICMR EAR values. By tribe, dietary inadequacy (IZiNCG EAR) was 39.5% among Bhil, 36.1% among Gond, and 51.3% among Korku. Stunting was observed in 29% (95% CI: 27.2–30.8) of participants overall, with rates of 32.9% in Bhil, 24.0% in Gond, and 29.0% in Korku. Low serum zinc (IZiNCG cut-offs: <70 µg/dl for females, <74 µg/dl for males fasting; <66 µg/dl females, <70 µg/dl males non-fasting) was detected in 57.5% (95% CI: 54.1–60.8) overall, with the highest prevalence in Bhil (70.2%), followed by Gond (59.9%) and Korku (36.1%). Using modified Indian cut-offs, low serum zinc prevalence was 34.4% overall (35.7% Bhil, 38.7% Gond, 26.9% Korku). Dietary inadequacy was higher in older adolescents (81.9% for 16–19 years vs. 30.6% for 10–12 years by ICMR EAR) and in boys (66.8%) compared to girls (63.0%). The phytate-to-zinc molar ratio exceeded 18, indicating poor zinc bioavailability from the cereal-based diet.

**Clinical Implications:** All three tribes exceeded the public health concern thresholds for zinc deficiency (≥25% inadequate intake, ≥20% stunting, ≥20% low serum zinc), confirming that zinc deficiency is a significant public health problem in this population. The high prevalence persists even after applying modified Indian cut-offs for serum zinc, with approximately one in three adolescents still classified as having low serum zinc. The findings highlight the need for multipronged interventions including dietary diversification, strategies to improve zinc bioavailability from plant-based diets, and inclusion of serum zinc estimation in national surveys. Limitations include the use of single-day dietary recall, potential overestimation of low serum zinc due to lack of inflammation adjustment (C-reactive protein not measured), and the cross-sectional design precluding causal inference.