Abstract
Evidence suggests a potentially causal relationship between systemic (blood and brain) iron status and performance on a range of measures of visual and cognitive performance. Unfortunately, the majority of this evidence involves coarse measures of visual and cognitive functioning, general measures that cannot address changes in the specific components of visual performance that may be affected by changes in iron status. We report an effort that in part tested the potential for increasing the resolution of the analysis of this relationship. Subjects (female tea pluckers, 19–55 years, in West Bengal, India) were randomly assigned to receive either iodized salt (control) or iodized salt fortified with iron (double-fortified salt, DFS). Blood indicators of iron status were measured at baseline (BL) and end line (EL), and included hemoglobin (Hb), serum ferritin (sFt), serum transferrin receptor (sTfR), body iron, and C-Reactive protein (CRP). Perceptual and cognitive functioning were assessed at BL and EL using six measures—visual reaction time, two measures of visual detection, the attentional network task, the composite face task, and a visual recognition memory task—selected for their potential for analyzing the components of perceptual and cognitive performance that might be most affected by changes in iron status. Prevalences of iron deficiency and iron deficiency anemia in the DFS group at EL were significantly lower than at BL and differed from the control group at EL. The DFS group showed significantly increased sFt and body iron, and significantly decreased sTfR at BL relative to EL and as compared to the controls, suggesting the efficacy of the dietary intervention. Almost all of the measures of visual performance were improved at EL for the DFS group, with variations across measures in terms of relative effects, providing a detailed analysis of change and allowing for specific hypotheses with respect to underlying brain mechanisms.
Mathile Institute for the Advancement of Human Nutrition and the Micronutrient Initiative.