Browsing by Author "Greenwood, Anna (Anya)"

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    The impact of vitamin D status on hepcidin and iron status in premenopausal females living in Auckland, New Zealand : a thesis presented in partial fulfilment of the requirements for the degree of Masters of Science in Nutrition and Dietetics, Massey University, Albany, New Zealand
    (Massey University, 2021) Greenwood, Anna (Anya)
    Background: Iron deficiency impacts female health, potentially leading to reduced immunity, cognitive function and physical performance. Hepcidin is a hormone that regulates iron homeostasis via the iron export channel ferroportin, subsequently controlling iron absorption, export and recycling. Supplementation of vitamin D has been demonstrated to reduce hepcidin concentration via direct transcription of the hepcidin gene (HAMP gene). However, the role of vitamin D and the impact on hepcidin and iron status has yet to be fully investigated. Aim: To investigate the associations between serum 25 hydroxyvitamin D (s-25(OH)D), hepcidin and iron status in premenopausal females living in Auckland New Zealand (NZ). The secondary aim is to investigate potential determinants of vitamin D status in premenopausal females. Methods: Pre-menopausal females aged 18-45 years, living in Auckland, New Zealand (NZ) participated in this cross-sectional study. Body composition was measured using bioelectrical impedance analysis and included: height, weight and body fat %. S-25(OH)D, inflammatory (CRP and IL-6), and iron biomarkers (serum ferritin, haemoglobin, soluble transferrin receptor and hepcidin) were measured from a venous blood sample. A series of questionnaires were completed to assess demographic and lifestyle factors, including: medical history, skin colour, sun exposure and dietary iron intake. Statistical analysis was undertaken using SPSS statistics 27 for windows (IBM). Results: Of the 160 participants included in the final analysis, 60 were NZ European, 67 South Asian and 33 from ‘other’ ethnicities. South Asians had significantly higher body fat % and IL-6 concentration (38.34% and 1.66 pg·mL⁻¹ respectively) compared to NZ Europeans, (27.49% and 0.63 pg·mL⁻¹ respectively, p<0.001). South Asians had significantly lower s-25(OH)D concentrations compared to NZ Europeans (33.59 nmol·L⁻¹ vs 74.84 nmol·L⁻¹, p<0.001). In NZ Europeans, higher s-25(OH)D concentrations were seen in those with lower (≤3.5nM) hepcidin concentration p=0.0046. Conversely, in South Asians, higher s-25(OH)D concentration was seen in those with higher (>3.5nM) hepcidin concentrations, p=0.038. There was no significant association in the ‘other’ ethnicities and no associations between s-25(OH)D and iron status/serum ferritin. Key determinants of s-25(OH)D were ethnicity, age and body fat %. Conclusion: The positive relationship between s-25(OH)D and hepcidin concentration in the South Asian women was unexpected, although possibly explained by higher IL-6 concentration, body fat % and lower s-25(OH)D concentration identified in the South Asian ethnic group, requiring further research.