Reference Cut-Offs to Define Low Serum Zinc Concentrations in 1-19 Year Old Indian Children and Adolescents

Abstract

Background: The quantification of population zinc (Zn) deficiency is based on serum zinc concentration (SZC) cut-offs, defined by International Zinc Nutrition Consultative Group (IZiNCG), derived from the 2·5th centile of age- and sex-specific SZC distributions from a high-income country. However, the SZC distributions, and its 2·5tthcentile cut-offs, can left-shift for a variety of reasons in lower middle-income countries (LMICs). The recent quality-controlled Indian Comprehensive National Nutrition Survey (CNNS) offered an opportunity to re-examine the SZC cut-offs in healthy 1–19-year-old children and adolescents and evaluate whether Zn deficiency was truly a public health problem in India. Methods: A healthy population (n=12473) of children was selected by including the highest 2 wealth quintiles, and excluding stunted, thin and obese children, and those with CRP >5mg/L, anemia, hypo-albuminemia, diabetes, recent diarrhea and a history of smoking. The 2·5th centile of the SZC distribution from this sample yielded the present cut-off to re-evaluate the prevalence of Zn deficiency against the IZiNCG cut-offs. Findings: The present study SZC cut-offs were significantly lower, by 10–18 µg/dL, than the IZiNCG cut-offs; more in adolescents. Thus, the prevalence of Zn deficiency in the entire CNNS sample, with the present cut-offs, was 2·7 to 5·5 times lower than with the IZiNCG cut-offs. No geographical state, nor any age group, showed Zn deficiency as a serious public health problem (≥20%). In contrast, with the IZiNCG cut-offs, between 9 to 27 states (depending on age group) had a serious public health problem with Zn deficiency. Interpretation: The present study reference SZC cut-offs for Zn deficiency are lower than the IZiNCG cut-offs, and since they were selected rigorously from a national sample, are more appropriate for use in India. A re-examination of the global applicability of IZiNCG recommended cut-offs to quantify Zn deficiency in other LMICs is required. Funding Source: CNNS is funded by The Mittal Foundation. However, there is no specific funding for this secondary analysis. Declaration of Interests: HSS designed the draft protocol of the CNNS with consultancy support from UNICEF, India. HSS, UK, and AVK were members of the Technical Advisory Committee of the CNNS, constituted by the Ministry of Health and Family Welfare of the Government of India, to oversee its conduct and analysis. HSS is a member of the WHO Nutrition Guidance Expert Advisory Subgroup on Diet and Health and Guideline Development Group on the use and interpretation of haemoglobin concentrations for assessing anaemia status in individuals and populations, member of the World Health Organization Nutrition Guidance Expert Advisory Subgroup on Diet and Health and Expert group on nutrient requirements: setting calcium, vitamin D and Zn nutrient intake values for children aged 0-4 years. He is also member of Expert Groups of the Ministry of Health and Family Welfare on Nutrition and Child Health. SD was involved in the CNNS study implementation. There were no other conflicts to declare. Ethics Approval Statement: The Population Council’s International Review Board (New York, USA) and the Ethics Committee of the Post Graduate Institute of Medical Education and Research (Chandigarh, India) gave ethical approval. Written consent from parent/caregiver for children under 10 years, consent of parent/caregiver as well as assent from adolescents (11-17 years) and written consent of adolescents above 17 years were obtained after due description of study details in local languages.