Billions worldwide consume inadequate levels of micronutrients critical to human health

Embargoed for release: Thursday, August 29, 6:30 PM ET

Key points:

• More than half of the global population consumes inadequate levels of several micronutrients essential to health, including calcium, iron, and vitamins C and E, according to new estimations.
• Micronutrient inadequacies may be more severe than previously thought and may differ between males and females.
• The results provide a roadmap for taking action by showing which population groups are at risk of deficiency for specific nutrients.

Boston, MA—More than half of the global population consumes inadequate levels of several micronutrients essential to health, including calcium, iron, and vitamins C and E, according to a new study by researchers at Harvard T.H. Chan School of Public Health, UC Santa Barbara (UCSB), and the Global Alliance for Improved Nutrition (GAIN). It is the first study to provide global estimates of inadequate consumption of 15 micronutrients critical to human health. 

The study will be published in The Lancet Global Health on August 29.

Micronutrient deficiencies are one of the most common forms of malnutrition globally, and each deficiency carries its own health consequences, from adverse pregnancy outcomes, to blindness, to increased susceptibility to infectious diseases. Previous research has estimated the amounts of micronutrients available to and consumed by people; this study evaluates whether these intakes meet requirements recommended for human health and looks at the inadequacies specifically facing males and females across their lifespans. 

“Our study is a big step forward,” said co-lead author Chris Free, research professor at UCSB. “Not only because it is the first to estimate inadequate micronutrient intakes for 34 age-sex groups in nearly every country, but also because it makes these methods and results easily accessible to researchers and practitioners.”

The researchers used data from the Global Dietary Database, the World Bank, and dietary recall surveys in 31 countries to compare nutritional requirements with nutritional intake among the populations of 185 countries. (They have made these data, as well as code for analysis, freely available.) They divided populations into males and females belonging to17 age groups: zero to 80 in five-year spans, as well as an 80+ group. The assessment studied fifteen vitamins and minerals: calcium, iodine, iron, riboflavin, folate, zinc, magnesium, selenium, thiamin, niacin, and vitamins A, B6, B12, C, and E.

The study found significant intake inadequacies for nearly all of the evaluated micronutrients, excluding fortification as a potential source of additional nutrients. Inadequate intake was especially prevalent for iodine (68% of the global population), vitamin E (67%), calcium (66%), and iron (65%). More than half of people consumed inadequate levels of riboflavin, folate, and vitamins C and B6. Intake of niacin was closest to sufficient, with 22% of the global population consuming inadequate levels, followed by thiamin (30%) and selenium (37%).

Estimated inadequate intakes were higher for women than men for iodine, vitamin B12, iron, and selenium within the same country and age groups. Conversely, more men consumed inadequate levels of calcium, niacin, thiamin, zinc, magnesium, and vitamins A, C, and B6 compared to women. While patterns of micronutrient inadequacy emerged more clearly on the basis of sex, the researchers also observed that males and females ages 10-30 were most prone to low levels of calcium intake, especially in South and East Asia and sub-Saharan Africa. Calcium intake was also low across North America, Europe, and Central Asia.

“These results are alarming,” said Ty Beal, senior technical specialist at GAIN. “Most people—even more than previously thought, across all regions and countries of all incomes—are not consuming enough of multiple essential micronutrients. These gaps compromise health outcomes and limit human potential on a global scale.”

“The public health challenge facing us is immense, but practitioners and policymakers have the opportunity to identify the most effective dietary interventions and target them to the populations most in need,” added senior author Christopher Golden, associate professor of nutrition and planetary health at Harvard Chan School.

The researchers noted that a lack of available data, especially on individual dietary intake worldwide, may have limited their findings.

Simone Passarelli, former doctoral student and postdoctoral research fellow in the Department of Nutrition at Harvard Chan School, served as co-lead author. She received funding from the National Institutes of Health (training grant 2T32DK007703-26).

“Global estimation of dietary micronutrient inadequacies: a modeling analysis,” Simone Passarelli, Christopher M. Free, Alon Shepon, Ty Beal, Carolina Batis, Christopher D. Golden, The Lancet Global Health, August 29, 2024, doi: 10.1016/S2214-109X(24)00276-6

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Harvard T.H. Chan School of Public Health brings together dedicated experts from many disciplines to educate new generations of global health leaders and produce powerful ideas that improve the lives and health of people everywhere. As a community of leading scientists, educators, and students, we work together to take innovative ideas from the laboratory to people’s lives—not only making scientific breakthroughs, but also working to change individual behaviors, public policies, and health care practices. Each year, more than 400 faculty members at Harvard Chan School teach 1,000-plus full-time students from around the world and train thousands more through online and executive education courses. Founded in 1913 as the Harvard-MIT School of Health Officers, the School is recognized as America’s oldest professional training program in public health.

The University of California, Santa Barbara is a leading research institution that also provides a comprehensive liberal arts learning experience. Teaching and research go hand-in-hand at UC Santa Barbara. Our students are full participants in an educational journey of discovery that stimulates independent thought, critical reasoning, and creativity. Our academic community of faculty, students, and staff is characterized by a culture of interdisciplinary collaboration that is responsive to the needs of our multicultural and global society. All of this takes place within a living and learning environment like no other, as we draw inspiration from the beauty and resources of our extraordinary location at the edge of the Pacific Ocean.

The Global Alliance for Improved Nutrition (GAIN) is a Swiss-based foundation launched at the United Nations in 2002 to tackle the human suffering caused by malnutrition. Working with governments, businesses, and civil society, we aim to transform food systems so that they deliver more nutritious foods for all people, especially the most vulnerable