Hidden No More: New Estimates Help the Nutrition Community Support Women and Children at Risk of Micronutrient Deficiencies

By Silvia Alayon, Director of Measurement, and Courtney Meyer, Publications Manager

Often referred to as “hidden hunger,” micronutrient deficiencies can have a deleterious effect on individuals, families, and communities. Worldwide, deficiencies in iron, vitamin A, zinc, and folate, among others, compromise immune systems, hinder child growth and development, and limit human capital.?

Nutrition and global health practitioners and researchers often mention that two billion people globally suffer from micronutrient deficiencies. However, for the last three decades, the methods used to make this prediction have not been readily available for researchers to update the estimate.

Timely data on the burden of micronutrient deficiencies is essential to understanding what works where and whether we’re making progress. With support from USAID through USAID Advancing Nutrition, a group of researchers including the Global Alliance for Improved Nutrition and the Global Micronutrient Deficiencies Research Group convened by the Micronutrient Forum, set out to estimate the global and regional prevalence of deficiencies in one or more micronutrients among preschool-age children and non-pregnant women of reproductive age and bring transparency to the process. Non-pregnant adolescent girls and women of reproductive age, pregnant women, and young children are particularly vulnerable to the effects of micronutrient malnutrition due to high dietary requirements and low diet quality.

The research team estimated the prevalence of deficiency in one or more of three key micronutrients—iron, zinc, and vitamin A for preschool-age children and iron, zinc, and folate for non-pregnant women—globally and in seven regions using 24 nationally-representative surveys collected between 2005 and 2019. (It is difficult to estimate deficiency in pregnant women due to the significant increase in their nutritional needs). Key findings include—

• Globally, an estimated 56 percent (or 372 million) of preschool-age children are deficient in at least one of three key micronutrients. Sixty-nine percent (or 1.2 billion) of nonpregnant women are affected.?
• The highest prevalence is in low- and middle-income countries. Three quarters of affected preschool-age children live in South Asia (99 million), Sub-Saharan Africa (98 million), or East Asia and the Pacific (85 million). Over half (57 percent) of affected non-pregnant women live in East Asia and the Pacific (384 million) or South Asia (307 million).
• Data gaps limit the researchers’ ability to estimate the burden of micronutrient deficiencies for all population groups.

Unlike previous estimates, which use proxy measures (e.g., stunting prevalence for zinc deficiency), this study relied on recent individual-level micronutrient status biomarkers. The team developed a standardized and transparent approach based on data availability, then used population-based surveys to create regional and global estimates. Finally, the authors share detailed methods so other researchers can replicate the results and periodically update these estimates.

Notably, the estimates are likely an underestimate of the true global burden of micronutrient malnutrition when considering all essential micronutrients, and all sexes and age groups. Due to lack of data, it was not possible to estimate the global prevalence of micronutrient deficiencies among school-aged children, men, and older adults. If these populations were considered, the total number of people experiencing micronutrient deficiencies is likely much larger than the oft-cited 2 billion. Some challenges in quantifying the global prevalence and number of people with micronutrient deficiencies include—

• Data availability: Population-based surveys don’t often contain micronutrient status biomarkers. Limited and often outdated data are available for preschool-age children and non-pregnant women, but even less data are available for?school-age children, adolescent boys, pregnant women, men, and older adults.?
• Difficult comparisons: Although recommendations on appropriate micronutrient status biomarkers and standardization of methodologies have been published, the variety in methods used limits the comparability of results.?
• Coexistence of deficiencies: Data on only a few of the 38 known essential nutrients are generally collected in surveys. Deficiencies do not always occur alone, but standardized methods to account for coexistence don’t yet exist.

Implementing partners like USAID Advancing Nutrition are working to increase the micronutrient intake of populations with improved diets, fortification of staple foods and condiments, crop biofortification, or supplementation. These efforts may reduce the burden of maternal and child morbidity, impaired cognitive development, and mortality.?

With a better understanding of the true global burden of undernutrition and key health issues, donors and policymakers can better support efforts to end hidden hunger and its impact on women and children.

Read the full study in Lancet Global Health.