Zinc deficiency results from an insufficient intake of zinc—primarily found in animal protein—as well as in whole-grain cereals, pulses, and legumes, especially if consumed with animal protein to reduce phytates negatively influencing absorption. Zinc deficiency can also be caused by poor absorption or excessive loss of the mineral. Because the human body cannot store zinc, a consistent supply of the mineral in the diet is necessary to fulfill zinc requirements (Lowe, Fekete, and Decsi 2009). Zinc is a catalyst for many enzymes that are needed for red blood cell production; as a result, zinc deficiency may be associated with anemia (Badham, Zimmermann, and Kraemer 2007). Available data suggest that zinc deficiency is widespread in low- and middle-income countries and is an important contributor to mortality and morbidity in children (Oruamabo 2015). For further information on zinc deficiency, visit the International Zinc Nutrition Consultative Group (IZiNCG) website: www.izincg.org.
How is zinc deficiency measured?
Insufficient zinc intake results in low serum/plasma levels of the mineral. In the face of increasing demand or lower dietary intake, the body maintains a mechanism to keep the blood levels of zinc steady by increasing the efficiency of absorption or reducing the excretion through the skin, kidney, and intestines. The status of populations is best measured by the zinc concentrations in serum/plasma (Fischer Walker and Black 2007), which can be determined using a venous blood sample and requires a cold chain. Based on availability, several instruments can be used to analyze zinc status, including flame atomic absorption spectrometry and inductively coupled plasma mass spectrometry (IZiNCG 2012).
In addition to direct measurement of serum/plasma zinc concentrations, inadequate zinc intake or stunting can be indirect indicators for the risk of zinc deficiency (Christine Hotz 2007; Fischer Walker and Black 2007). When using zinc intake to measure deficiency, also calculate phytate intake to estimate zinc absorption.
How is zinc deficiency categorized?
Zinc deficiency is considered to be a public health concern when the prevalence of low serum/plasma zinc concentration is higher than 20 percent (IZiNCG 2007). Cut-offs for zinc deficiency are defined in Table 9; they depend on the age, sex, and fasting status of the study participant, as well as the time of day the blood was collected.
Table 9: Zinc Deficiency Cut-Offs Based on Zinc Concentration (microgram/deciliter)
| Time of Day and Fasting Status | Suggested Lower Cut-Offs for Serum Zinc Concentration (mcg/dL) | ||
|---|---|---|---|
| 10 years | ≥10 years | ||
| Males and females | Non-pregnant females | Males | |
| Morning fasting | Not available | 70 | 74 |
| Morning non-fasting | 65 | 66 | 70 |
| Afternoon non-fasting | 57 | 59 | 61 |
Source: IZiNCG 2012
Where can we get these data?
Zinc deficiency is measured in population-based surveys and research studies conducted among children and, sometimes, women of reproductive age. Of the commonly administered population-based surveys, the National Micronutrient Survey is usually the only one that collects and analyzes information on the prevalence of zinc deficiency.
Methodological issues
- Serum/plasma zinc status relies on age, sex, fasting status, and time of day of blood collection, and thus to calculate the relevant cut-offs, studies must collect all this information (Hess et al. 2007). If these data are not collected, then the results of the study may not accurately reflect the population zinc status and it should be noted as a limitation.
- Look at the quality of data collection. Because zinc is found in serum/plasma in trace amounts, the sample’s risk of contamination with external zinc is very high, and is a major source of measurement error (IZiNCG 2012). Often, you will not have information on the quality of data collection unless you were directly involved in the data collection or have obtained this information from those that undertook the survey. If you have this information, include it in your report.
- Serum/plasma zinc it is not a reliable indicator of deficiency at the individual level (IZiNCG 2012).