Effect of Oral Iron Supplementation on Cognitive Function among Children and Adolescents in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis

Associations between Serum Iron Indices and Self-Assessed Multiple Intelligence Scores among Adolescents in Riyadh, Saudi Arabia

Micronutrient deficiencies, including iron deficiency, are linked to different cognitive impairments and sensory functions. However, whether circulating iron levels affect self-assessed multiple intelligence (MI) scores in adolescents remains uninvestigated. This study aimed to investigate associations between serum iron levels and self-assessed MI scores in adolescents in Riyadh, Saudi Arabia. Recruiting 434 Saudi adolescents (174 boys and 260 girls, aged 12-17), we administered the McKenzie questionnaire to assess MI across nine categories. Anthropometrics and fasting blood samples were collected to measure circulating iron and transferrin levels. Total iron-binding capacity (TIBC) and transferrin saturation (TSAT) levels were calculated. Notably, girls exhibited significantly higher MI scores in the interactive domain than boys (age and BMI-adjusted OR = 1.36, 95% confidence interval = 1.07-1.73, p = 0.01). No significant correlations were observed between serum iron and MI. However, normal TSAT levels (TSAT > 20%) corresponded with higher age and BMI-adjusted odds of MI scores in the musical (OR = 1.59, 95%CI = 1.1-2.2, p = 0.006), linguistic (1.57, 1.1-2.3, p = 0.016), kinesthetic (1.48, 1.1-2.1, p = 0.024), spatial (1.45, 1.1-2.1, p = 0.03), and existential (1.56, 1.1-2.1, p = 0.01) categories compared to ones with lower TSAT levels (TSAT ≤ 20%), only in boys. In conclusion, serum iron levels may not directly influence MI domains in adolescents in Riyadh, Saudi Arabia; however, lower TSAT levels, indicative of iron-deficiency anemia, may influence MI, only in boys, indicating a possible relationship between iron metabolism and cognitive functions.

Recommendations for diagnosis, treatment, and prevention of iron deficiency and iron deficiency anemia

Iron is an essential nutrient and a constituent of ferroproteins and enzymes crucial for human life. Generally, nonmenstruating individuals preserve iron very efficiently, losing less than 0.1% of their body iron content each day, an amount that is replaced through dietary iron absorption. Most of the iron is in the hemoglobin (Hb) of red blood cells (RBCs); thus, blood loss is the most common cause of acute iron depletion and anemia worldwide, and reduced hemoglobin synthesis and anemia are the most common consequences of low plasma iron concentrations. The term iron deficiency (ID) refers to the reduction of total body iron stores due to impaired nutrition, reduced absorption secondary to gastrointestinal conditions, increased blood loss, and increased needs as in pregnancy. Iron deficiency anemia (IDA) is defined as low Hb or hematocrit associated with microcytic and hypochromic erythrocytes and low RBC count due to iron deficiency. IDA most commonly affects women of reproductive age, the developing fetus, children, patients with chronic and inflammatory diseases, and the elderly. IDA is the most frequent hematological disorder in children, with an incidence in industrialized countries of 20.1% between 0 and 4 years of age and 5.9% between 5 and 14 years (39% and 48.1% in developing countries). The diagnosis, management, and treatment of patients with ID and IDA change depending on age and gender and during pregnancy. We herein summarize what is known about the diagnosis, treatment, and prevention of ID and IDA and formulate a specific set of recommendations on this topic.

Improving Cognitive Function with Nutritional Supplements in Aging: A Comprehensive Narrative Review of Clinical Studies Investigating the Effects of Vitamins, Minerals, Antioxidants, and Other Dietary Supplements

Cognitive impairment and dementia are burgeoning public health concerns, especially given the increasing longevity of the global population. These conditions not only affect the quality of life of individuals and their families, but also pose significant economic burdens on healthcare systems. In this context, our comprehensive narrative review critically examines the role of nutritional supplements in mitigating cognitive decline. Amidst growing interest in non-pharmacological interventions for cognitive enhancement, this review delves into the efficacy of vitamins, minerals, antioxidants, and other dietary supplements. Through a systematic evaluation of randomized controlled trials, observational studies, and meta-analysis, this review focuses on outcomes such as memory enhancement, attention improvement, executive function support, and neuroprotection. The findings suggest a complex interplay between nutritional supplementation and cognitive health, with some supplements showing promising results and others displaying limited or context-dependent effectiveness. The review highlights the importance of dosage, bioavailability, and individual differences in response to supplementation. Additionally, it addresses safety concerns and potential interactions with conventional treatments. By providing a clear overview of current scientific knowledge, this review aims to guide healthcare professionals and researchers in making informed decisions about the use of nutritional supplements for cognitive health.

Influence of intermittent iron and folic acid supplementation on cognitive abilities among adolescent girls in northwestern Tanzania

Iron and folic acid (IFA) supplementation to reduce anemia is key for improving substantial lost disability adjusted life years (DALYs) for adolescent girls. This study assessed the impact of weekly IFA supplementation (WIFAS) on cognitive ability among adolescent girls in the Simiyu Region in northernwestern Tanzania. This cross-sectional comparative evaluation study of 770 adolescent girls (396 -WIFAS supplemented; 374 -not supplemented) evaluated the association between WIFAS and cognitive ability through a face-to-face survey and cognitive ability assessment using standardized tests (Span-forward Test, Span-backward Test and Maze Test). Using a modified Poisson regression, we controlled for the geographic setting (urban vs rural), availability of potable water and feeding programs in schools, age and school level of adolescent girls, parental status, main parental economic activities, and the number of teachers. Participants were between the ages of 11 and 19 years, with more than half (57%) between 12-15 years of age. Those with WIFAS had higher cognitive ability (Span-forward scores, χ2 = 46.34% p <0.001; Span-forward, χ2 = 46.34% p <0.001; and Global Composite Cognitive Performance (GCCP), χ2 = 32.52% p<0.001). Among the IFA supplemented adolescent girls, secondary school level had a significantly higher score with respect to Span-backward (aPR = 1.43, 95% CI = 1.06-1.62); Span-forward ability (aPR = 1.26, 95% CI = 1.04-1.53) and Maze Test ability (aPR = 1.12, 95% CI = 1.01-1.25) as compared to their counterpart in primary school level. Individual adolescent girls with WIFAS and living with both parents performed much better on the Span-backward Test (aPR = 1.22, 95% CI = 1.07-1.68) as compared to those living with relatives and/or orphans. The presence of potable water program among the WIFAS schools resulted in a higher Span-backward ability (aPR = 1.34, 95% CI = 1.03-1.89); and GCCP (aPR = 1.27, 95% CI = 1.03-1.75). Adolescent girls from WIFAS schools with feeding program had higher Span-forward (aPR = 1.38, 95% CI = 1.03-1.63) ability as well as a higher Maze Test (aPR = 1.15, 95% CI = 1.07-1.26) score. The present study provides compelling evidence that WIFAS is positively associated with higher cognitive ability among adolescent girls. Nevertheless, IFA interventions are still rare in communities across Tanzania.

Effects of iron supplementation on cognitive development in school-age children: Systematic review and meta-analysis

BACKGROUND

Iron deficiency is negatively associated with children's cognitive development. Evidence showed that iron supplementation improves cognitive development. Nearly 50% of anemia is caused by iron deficiency. Anemia affects more school-age children, at an age where their brain development continues. The aim of this systematic review and meta-analysis is to review the evidence from published randomized controlled trials to evaluate the effects of iron supplementation on cognitive development and function among school-age children.

METHOD

Five databases including MEDLINE, EMBASE, Scopus, Web of Science and CENTRAL were used to search for articles on April 20th, 2021. The search was reconducted on October 13th, 2022 to retrieve new records. Studies were eligible if they included school children 6-12 years of age, were randomized controlled trials, and if they tested iron supplementation and measured cognitive development.

RESULT

Thirteen articles were included in the systematic review. Overall, iron supplementation significantly improved intelligence (standardized mean difference, 95% confidence interval) (SMD 0.46, 95%CI: 0.19, 0.73, P<0.001), attention and concentration (SMD 0.44, 95%CI: 0.07, 0.81, P = 0.02) and memory (SMD 0.44, 95%CI: 0.21, 0.67, P <0.001) of school-age children. There was no significant effect of iron supplementation on school achievement of school-age children (SMD 0.06, 95%CI: -0.15, 0.26, P = 0.56). In a subgroup analysis, iron-supplemented children who were anemic at baseline had had better outcomes of intelligence (SMD 0.79, 95%CI: 0.41, 1.16, P = 0.001) and memory (SMD 0.47, 95%CI: 0.13, 0.81; P = 0.006).

CONCLUSION

Iron supplementation has a significant positive effect on the intelligence, attention and concentration, and the memory of school-age children but there was no evidence on the effect of iron supplementation on their school achievement.