India’s 2016-2018 Comprehensive National Nutrition Survey (CNNS) is a truly admirable undertaking, as it is one of the largest micronutrient surveys ever conducted. This month, full results of the serum zinc status of children and adolescents were published in the American Journal of Clinical Nutrition with an accompanying editorial.
Serum zinc concentrations (SZC) were assessed in more than 28,000 pre-schoolers, school aged children, and adolescents. Nationally, the prevalence of low SZC was 31.1% among adolescents, 15.8% among school-aged children and 17.4% among preschool children. State-level prevalence estimates ranged from 2.4% in Mizoram to 38.8% in Himachal Pradesh, using data for pre-school children as an example. By providing much-needed data on zinc status at the national- and state- levels, the CNNS highlights the importance of biochemical data on micronutrient status to guide the targeting of interventions to the most vulnerable populations.
It is helpful to start with what these prevalence estimates actually mean. India is the second most populous country in the world. While the prevalence of low SZC among children and adolescents may be lower in comparison to most of the 26 other low- and middle-income countries with available data on SZC, the CNNS findings indicate that approximately 38 million Indian children and 71 million Indian adolescents have an elevated risk of zinc deficiency. Those are staggering numbers.
It is important for individual governments to decide upon criteria to define national public health problems given a variety of contextual factors. However, IZiNCG considers the risk of zinc deficiency to be of public health concern when the prevalence of low SZC is higher than 20%. This means that, at 31.1%, the prevalence of low SZC among adolescents calls for further investigation and action, particularly considering the intergenerational cycle of undernutrition and the fact that many girls who are zinc-deficient in adolescence will likely continue to be zinc-deficient during pregnancy in the absence of any intervention.
Although the national prevalence estimates for zinc deficiency among pre-school and school-aged children were below 20%, state-level analyses revealed that the prevalence of zinc deficiency among preschool and school-aged children exceeded the 20% threshold in 10 out of 30 and 8 out of 30 states, respectively.
Drilling down further, the results show that low SZC was more common among preschool children with rural residence, mothers with lower levels of education, and poorer household socioeconomic status and sanitation facilities. These findings identify vulnerable subgroups that should be prioritized to receive zinc interventions through existing platforms such as the Public Distribution System, Mid-day Meal program, and the Integrated Child Development Services, as well as new delivery channels.
An excellent review of the survey’s methods can be found in the editorial by Brown et al. As these authors note, no external quality assessments were reported for the laboratory assessment of SZC, which highlights the need for an easily accessible, global laboratory standardization program for SZC analysis.
In summary, the government of India is to be commended for undertaking such a monumental survey and generating the data needed to guide future interventions. The next challenge is to develop programs to address zinc and other micronutrient deficiencies in populations most in need.