Abstract
Manganese (Mn) plays a dual role in the body, acting as an essential trace element and a potential toxicant, the effects of which depend on its levels. In addition to food, exposure can occur through polluted air and contaminated water. Animal studies suggest that increased retention and absorption of Mn might result from iron deficiency, as both share similar physicochemical properties. However, human evidence is incomplete. This study aimed to confirm and expand upon prior findings that iron status influences Mn kinetics in the U.S. female population. The analysis included 1255 non-pregnant females aged 12-49 years with valid urinary and blood Mn and iron measurements as part of the 2015-2018 National Health and Nutrition Examination Survey. Iron status was assessed with a total body iron (TBI) score calculated from measured serum ferritin and the transferrin receptor. Iron deficiency was defined as a TBI score < 0. Demographic and laboratory characteristics (e.g. age and kidney function) were recorded. Among the study participants, roughly 8.8% were found to have iron deficiency. Conversely, 16.9% of participants exhibited blood Mn levels exceeding 1.5 µg/dL, a commonly used reference. On average, blood Mn was approximately 40% higher in subjects considered iron deficient than in their counterparts after controlling for covariates such as race. Those with iron deficiency also had a lower urine-to-blood Mn ratio. The findings suggest that iron-deficient females may have greater Mn accumulation, increasing the risk of Mn toxicity. Further investigations should include male populations to complement the current findings.