The effect of age on intestinal iron uptake

Abstract

Background: The pro-oxidant role of iron in neurodegenerative and chronic disease has led to concern over the danger of excessive levels posing a health risk (Kell, 2009). As the body has limited capacity to excrete iron, absorption acts as the main homeostatic mechanism (Anderson et al., 2009). Although iron stores increase with age (Liu et al., 2003), the effect of advancing age on iron regulation has not been extensively studied and age related misregulation has been implied (Levenson et al., 2004). The aim of this study was to investigate the effect of age on intestinal iron uptake in adults. Method: Thirty-five participants (29 females and six males subdivided into three age groups) provided fasted blood samples. A second sample was taken three hours following a standard breakfast (low in iron inhibitors and enhancers) and a 200 mg iron sulphate supplement as used by Hutchinson et al. (2004). Total plasma iron, total iron binding capacity (TIBC), transferrin saturation (TSAT) and non-transferrin bound iron (NTBI) were measured. Participants completed a 52 item food frequency questionnaire, adapted from the validated EPIC-Norfolk study to be iron specific. Data was statistically analysed using anova and Pearson regression. Approval was granted by the University of Plymouth Ethical Committee. Results: Total plasma iron absorption and post supplement increases in TSAT and NTBI were greatest in the 35–55 years age group (Table 1). TIBC and iron intake were similar for all groups. A weak correlation was found between iron uptake and change in NTBI (r = 0.405, P < 0.022). Table 1. Mean (SD) plasma analysis, standard deviation and significance between groups Variable 18–34 years 35–55 years 56+ years Significance Δ = change, PP = postprandial, TIBC = total iron binding capacity, TSAT = transferrin saturation. Δ In Iron μM 11.9 (17.4) 20.8 (10) 6.2 (7.4) P < 0.051 Δ In NTBI μM 0.24 (0.36) 1.09 (1.48) 0.29 (0.5) P < 0.060 TIBC μM 102 (23) 92 (23) 97 (11) P < 0.525 % TSAT (PP) 49 (13) 60 (9) 41 (9) P < 0.014 Iron Intake (mg) 66 (29) 67 (21) 73 (1) P < 0.747 Discussion: This study does not support the suggestion that iron absorption is misregulated in older age (Levenson et al., 2004) but does support the ‘set point’ theory that iron uptake increases with age until a certain point (Garry et al., 2000). In healthy individuals the plasma concentration of NTBI is small; the elevated amount found in the 35–55 year age group is of some concern. This study examined a small, predominantly female sample and the results may have been affected by factors that were not considered such as menstruation, menopause and contraceptive use. Conclusion: It is possible that iron absorption is greater in the middle years of life and that this increases both stores and pro-oxidant damage, which in later years manifests into chronic disease. This study may provide new insight into iron regulation and warrants further research.