Anemia affects a third of the world's population and contributes to increased morbidity and mortality, decreased work productivity, and impaired neurological development. Understanding anemia's varied and complex etiology is crucial for developing effective interventions that address the context-specific causes of anemia and for monitoring anemia control programs. We outline definitions and classifications of anemia, describe the biological mechanisms through which anemia develops, and review the variety of conditions that contribute to anemia development. We emphasize the risk factors most prevalent in low-and middle-income countries, including nutritional deficiencies, infection/inflammation, and genetic hemoglobin disorders. Recent work has furthered our understanding of anemia's complex etiology, including the proportion of anemia caused by iron deficiency (ID) and the role of inflammation and infection.Accumulating evidence indicates that the proportion of anemia due to ID differs by population group, geographical setting, infectious disease burden, and the prevalence of other anemia causes. Further research is needed to explore the role of additional nutritional deficiencies, the contribution of infectious and chronic disease, as well as the importance of genetic hemoglobin disorders in certain populations.

Home fortification of foods with multiple micronutrient powders for health and nutrition in children under two years of age.

An increasing recognition has emerged of the complexities of the global health agenda—specifically, the collision of infections and noncommunicable diseases and the dual burden of over- and undernutrition. Of particular practical concern are both 1) the need for a better understanding of the bidirectional relations between nutritional status and the development and function of the immune and inflammatory response and 2) the specific impact of the inflammatory response on the selection, use, and interpretation of nutrient biomarkers. The goal of the Inflammation and Nutritional Science for Programs/Policies and Interpretation of Research Evidence (INSPIRE) is to provide guidance for those users represented by the global food and nutrition enterprise. These include researchers (bench and clinical), clinicians providing care/treatment, those developing and evaluating programs/interventions at scale, and those responsible for generating evidence-based policy. The INSPIRE process included convening 5 thematic working groups (WGs) charged with developing summary reports around the following issues: 1) basic overview of the interactions between nutrition, immune function, and the inflammatory response; 2) examination of the evidence regarding the impact of nutrition on immune function and inflammation; 3) evaluation of the impact of inflammation and clinical conditions (acute and chronic) on nutrition; 4) examination of existing and potential new approaches to account for the impact of inflammation on biomarker interpretation and use; and 5) the presentation of new approaches to the study of these relations. Each WG was tasked with synthesizing a summary of the evidence for each of these topics and delineating the remaining gaps in our knowledge. This review consists of a summary of the INSPIRE workshop and the WG deliberations.

The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2019 provides a rules-based synthesis of the available evidence on levels and trends in health outcomes, a diverse set of risk factors, and health system responses. GBD 2019 covered 204 countries and territories, as well as first administrative level disaggregations for 22 countries, from 1990 to 2019. Because GBD is highly standardised and comprehensive, spanning both fatal and non-fatal outcomes, and uses a mutually exclusive and collectively exhaustive list of hierarchical disease and injury causes, the study provides a powerful basis for detailed and broad insights on global health trends and emerging challenges. GBD 2019 incorporates data from 281 586 sources and provides more than 3•5 billion estimates of health outcome and health system measures of interest for global, national, and subnational policy dialogue. All GBD estimates are publicly available and adhere to the Guidelines on Accurate and Transparent Health Estimate Reporting. From this vast amount of information, five key insights that are important for health, social, and economic development strategies have been distilled. These insights are subject to the many limitations outlined in each of the component GBD capstone papers.

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Home fortification of foods with multiple micronutrient powders is an effective intervention to reduce anaemia and iron deficiency in children six months to 23 months of age. The provision of MNP is better than no intervention or placebo and possibly comparable to commonly used daily iron supplementation. The benefits of this intervention as a child survival strategy or on developmental outcomes are unclear. Data on effects on malaria outcomes are lacking and further investigation of morbidity outcomes is needed. The micronutrient powders containing multiple nutrients are well accepted but adherence is variable and in some cases comparable to that achieved in infants and young children receiving standard iron supplements as drops or syrups.

Anemia remains a widespread public health problem. Although iron deficiency is considered the leading cause of anemia globally, the cause of anemia varies considerably by country. To achieve global targets to reduce anemia, reliable estimates of the contribution of nutritional and non-nutritional causes of anemia are needed to guide interventions. Inflammation is known to affect many biomarkers used to assess micronutrient status and can thus lead to incorrect diagnosis of individuals and to overestimation or underestimation of the prevalence of deficiency in a population. Reliable assessment of iron status is particularly needed in settings with high infectious disease burden, given the call to screen for iron deficiency to mitigate potential adverse effects of iron supplementation. To address these information gaps, in 2012 the CDC, National Institute for Child Health and Human Development, and Global Alliance for Improved Nutrition formed a collaborative research group called Biomarkers Reflecting Inflammation and Nutrition Determinants of Anemia (BRINDA). Data from nationally and regionally representative nutrition surveys conducted in the past 10 y that included preschool children and/or women of childbearing age were pooled. Of 25 data sets considered for inclusion, 17 were included, representing ∼30,000 preschool children, 26,000 women of reproductive age, and 21,000 school-aged children from all 6 WHO geographic regions. This article provides an overview of the BRINDA project and describes key research questions and programmatic and research implications. Findings from this project will inform global guidelines on the assessment of anemia and micronutrient status and will guide the development of a research agenda for future longitudinal studies.

Iron deficiency is a global problem across the life course, but infants and their mothers are especially vulnerable to both the development and the consequences of iron deficiency. Maternal iron deficiency during pregnancy can predispose offspring to the development of iron deficiency during infancy, with potentially lifelong sequelae. This review explores iron status throughout these “first 1000 days” from pregnancy through two years of age, covering the role of iron and the epidemiology of iron deficiency, as well as its consequences, identification, interventions and remaining research gaps.