Iron status and iron-vitamin C co-supplementation effects on cognition, subjective mood and fatigue in menstruating, non anaemic women aged 18–49 years

Avery, Hannah Louise (2021) Iron status and iron-vitamin C co-supplementation effects on cognition, subjective mood and fatigue in menstruating, non anaemic women aged 18–49 years. Doctoral thesis, Northumbria University.

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Abstract

Iron is an essential nutrient required for numerous biological processes, particularly concerning brain function. However, iron deficiency is the most prevalent nutrient deficiency worldwide. Although previous research regarding the effects of iron status and iron supplementation on psychological and physiological outcomes is extensive, there are several methodological limitations relating to heterogeneity in iron status cut-offs, sample populations, and supplementation dosage, duration and formulations. Research has also largely focused on iron deficiency anaemia with less known about non-anaemic iron deficiency (NAID), despite the increased prevalence of NAID among women of reproductive age. Therefore, this thesis aimed to investigate iron status and the effects of iron bis-glycinate chelate supplementation on cognitive function, subjective fatigue, mood and wellbeing in iron sufficient (IS) and NAID women of reproductive age. Vitamin C co supplementation was also explored as well as any differential effects of this on cognitive function, subjective fatigue, mood and wellbeing.

Chapter 2 describes a cross-sectional study that explored the association of haemoglobin and serum ferritin with cognition, subjective mood, fatigue and wellbeing whilst controlling for the confounding effects of dietary iron, menstrual blood loss, physical activity and body mass index. Chapter 3 describes a systematic review of findings from randomised controlled trials investigating the effects of iron supplementation on cognitive function, mood, fatigue and/or wellbeing in women of reproductive age. Chapters 4 and 5 describe randomised, placebo-controlled, parallel groups trials of a 16-week intervention with iron bis-glycinate chelate or iron/vitamin C co-supplementation. Effects on cognition, subjective mood, fatigue and wellbeing (Chapter 4) and cerebral haemodynamics and whole-body energy metabolism at rest and during cognitive demand (Chapter 5) were assessed in IS and NAID females.

Serum ferritin concentrations were positively associated with emotional functioning and mental health. Although iron status improved following iron/vitamin C co-supplementation, treatment effects of both iron and iron/vitamin C were limited and mixed. Iron treatment alone reduced feelings of depression and total mood disturbance yet engendered an unexpected reduction in physical component summary scores. However, iron/vitamin C treatment resulted in improved serial subtraction accuracy whilst increased total haemoglobin concentrations were found during cognitive demand for NAID women compared to IS women. Taken together, these findings suggest that iron treatment can be beneficial for certain aspects of psychological functioning and that the lack of cognitive differences between NAID and IS women of reproductive age may be due to cerebral haemodynamic compensation.

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