Q&A: Global burden of dietary iron deficiency

A new study examined global burden of dietary iron deficiency, focusing on where inadequate dietary iron intake leads to clinical manifestations such as anemia. Study authors analyzed data from the Global Burden of Disease study 2021 to estimate dietary iron deficiency prevalence and disability-adjusted life years, stratified by age, sex, geography and socio-demographic index across 204 countries. 

We speak with co-author of the study, Dr. Nicholas J Kassebaum, Adjunct Professor in Health Metric Sciences and Global Health at IHME.

This transcript has been lightly edited for clarity

What is unique about the research just published, and why was it undertaken?

The unique aspect of the research that was just published is the first-ever quantification, in published form, of the burden of dietary iron-deficiency anemia.

Most of the time what we look at is either all of iron deficiency combined, or all of anemia combined, both of which, of course, are huge public health problems. But the interventions for those can be tricky, whereas dietary iron deficiency can be really amenable to potentially – or at least conceptually –simple interventions like supplementation, improved diet, and other population-level efforts.

What are the key findings of the research?

Some of the key findings relate to sex differences, age differences, and geographic differences. So first – I’ll start off with the fourth one – is that over time, the situation definitely is improving, albeit slowly. And the reason that it’s slow is because the burden is largest in children, and it’s largest in women of reproductive age, so what we would say is 15–49-year-old females. And it’s highest in places where societal development is not as strong and there are maybe more nutritional challenges, more infectious challenges, and a lot of different disease pressures on the population.

Where is the burden of dietary iron deficiency the greatest, by DALYs and prevalence?

What we see when looking at the map of DALYs due to dietary iron deficiency is that the burden is highest in the lower-resource settings, including many countries in Africa and South Asia.

In 1990, the rates were highest in West Africa, some parts of the Sahel, through Central Africa and into the Horn of Africa, as well as India, Pakistan, and Bangladesh. Fast-forwarding to 2021, what we see is that there was quite a bit of improvement in many of the countries, but a number of countries actually didn’t improve that much at all – and those were mostly Yemen and a couple of countries in West Africa.

Looking at the maps of prevalence, in the age-standardized fashion, of anemia between 1990 and 2021, we see patterns where the burden is highest in Africa and South Asia – and in Africa, it’s most concentrated in the countries of Western Africa.

Fast-forward into 2021, we see broad improvement, but really stagnation in West Africa and some parts of South Asia where the burden is even more concentrated than it was 25 years ago.

What differences did you uncover between genders?

What we see in youngest kids, males and females, the rates of dietary iron-deficiency anemia are pretty much equivalent. But as females enter into their reproductive years, or after menarche, throughout the entire adulthood, females have much higher rates of anemia and dietary iron-deficiency anemia, probably because the requirements are higher, maybe they have less access to nutritious foods, maybe a little bit less autonomy to pursue those foods in some settings.

And then what we see after menopause in older adults is that the rates of dietary iron-deficiency anemia, again, equilibrate between males and females.

How do prevalence and DALYs differ when looking at the burden of dietary iron deficiency?

Prevalence is a good way to see how many people are affected by this condition. DALYs is a somewhat more precise measure of what is the cumulative impact of this condition.

When we look at the overall number of cases, the number of DALYs, versus the rate, which is the number of persons per population, what we see is actually divergent trends. So as seen here on the left, the number of DALYs has actually increased globally from 1990 through 2021, from just under 3 million to about 3.25 million in that time.

Meanwhile, the rate of DALYs, the number of people within the population who have experienced the burden of dietary iron-deficiency anemia, has actually gone down a fair amount during that same period. And the patterns we see in prevalence are broadly similar. This reflects the fact that while we’ve made some dent on the most severe forms of dietary iron-deficiency anemia, because of population growth and because of the persistence of the problem, it remains a huge specter throughout the world.

What action is needed to reduce iron deficiency?

What needs to be done to address dietary iron-deficiency anemia – the reason I say it’s conceptually simple is because we need to give people more iron. And the conceptually simple part of that is, well, just eat more iron, or take more iron supplements, or take more intravenous iron or other treatments like that.  

What needs to happen more is understanding, well, what are the reasons that people are not getting that already? What are the barriers to being able to access the foods they need? If they are accessing and eating the foods that they’re supposed to, or that would be nutritious, are there certain factors like malabsorption, or gastrointestinal problems, or autoimmune diseases, or chronic infections, or other factors of the diet that are preventing them from being able to absorb the iron? Or are there other factors in their biology that are preventing their body from being able to utilize the iron that’s there? So it’s all related, and the simple answer is give more iron. But there’s a lot more to it in figuring out those reasons and what’s actually going to work.