Estimating the global prevalence of zinc deficiency: results based on zinc availability in national food supplies and the prevalence of stunting

Abstract

Background: Adequate zinc nutrition is essential for adequate growth, immunocompetence and neurobehavioral development, but limited information on population zinc status hinders the expansion of interventions to control zinc deficiency. The present analyses were conducted to: (1) estimate the country-specific prevalence of inadequate zinc intake; and (2) investigate relationships between country-specific estimated prevalence of dietary zinc inadequacy and dietary patterns and stunting prevalence.

Methodology and principal findings: National food balance sheet data were obtained from the Food and Agriculture Organization of the United Nations. Country-specific estimated prevalence of inadequate zinc intake were calculated based on the estimated absorbable zinc content of the national food supply, International Zinc Nutrition Consultative Group estimated physiological requirements for absorbed zinc, and demographic data obtained from United Nations estimates. Stunting data were obtained from a recent systematic analysis based on World Health Organization growth standards. An estimated 17.3% of the world's population is at risk of inadequate zinc intake. Country-specific estimated prevalence of inadequate zinc intake was negatively correlated with the total energy and zinc contents of the national food supply and the percent of zinc obtained from animal source foods, and positively correlated with the phytate: zinc molar ratio of the food supply. The estimated prevalence of inadequate zinc intake was correlated with the prevalence of stunting (low height-for-age) in children under five years of age (r = 0.48, P<0.001).

Conclusions and significance: These results, which indicate that inadequate dietary zinc intake may be fairly common, particularly in Sub-Saharan Africa and South Asia, allow inter-country comparisons regarding the relative likelihood of zinc deficiency as a public health problem. Data from these analyses should be used to determine the need for direct biochemical and dietary assessments of population zinc status, as part of nationally representative nutritional surveys targeting countries estimated to be at high risk.

Figure 1. Estimated country-specific prevalence of inadequate zinc intake.

Data are based on the composite nutrient composition database, IZINCG physiological requirements, the Miller Equation to estimate zinc absorption and an assumed 25% inter-individual variation in zinc intake. Data are for the 2005 time frame (2003–2007).

Figure 2. Percentage of total zinc in national food supplies derived from (a) all food sources and (b) cereal and non-cereal sources.

Regional data are weighted by national population size and listed in ascending order according to the estimated prevalence of inadequate zinc intake in the region. HIGHIN, High-income; SOTRLA, Southern and Tropical Latin America; CHINAR, China; CEEAEU, Central and Eastern Europe; CALACA, Central and Andean Latin America and the Caribbean; CANAME, Central Asia, North Africa and the Middle East; ESEASP, East and South-East Asia and the Pacific; SUSAAF, Sub-Saharan Africa; SOASIA, South Asia. Data are for the 2005 time frame (2003–2007).

Figure 3. Relationship between availability of (a) energy (kcal/capita/d) and (b) total zinc (mg/capita/d) in the national food supply and the estimated prevalence of inadequate zinc intake.

N = 188. Data are for the 2005 time frame (2003–2007).

Figure 4. Relationship between (a) the percentage of zinc from animal source foods and (b) the phytate:zinc molar ratio in the national food supply and the estimated prevalence of inadequate zinc intake.

N = 188. Data are for the 2005 time frame (2003–2007).

Figure 5. Secular trends in the global and regional estimated prevalence of inadequate zinc intake between 1990 and 2005.

SOASIA, South Asia; SUSAAF, sub-Saharan Africa; ESEASP, East and South-East Asia and the Pacific; CANAME, Central Asia, North Africa and the Middle East; CALACA, Central and Andean Latin America and the Caribbean; CEEAEU, Central and Eastern Europe; CHINAR, China; HIGHIN, High-income; SOTRLA, Southern and Tropical Latin America.

Figure 6. Relationship between the estimated prevalence of inadequate zinc intake and the prevalence of childhood stunting.

Stunting data (low height-for-age) are for children less than five years of age in138 low- and middle-income countries. The solid line represents the line of identity (intercept = 0, slope = 1). The dashed line represents the best-fit regression line. Dotted lines demarcate prevalence data associated with low, moderate and high risk of inadequate zinc intake, based on the composite index of both variables.

Figure 7. National risk of zinc deficiency based on the prevalence of childhood stunting and the estimated prevalence of inadequate zinc intake.

Stunting data (low height-for-age) are for children less than five years of age in138 low- and middle-income countries. The estimated prevalence of inadequate zinc intake is based on the FAO national food balance sheet data, the composite nutrient composition database, IZINCG physiological requirements, the Miller Equation to estimate zinc absorption and an assumed 25% inter-individual variation in zinc intake.