Relationship between vitamin D, iron, and hepcidin in premenopausal females, potentially confounded by ethnicity.

PURPOSE: To investigate the associations between vitamin D, hepcidin, and iron status in premenopausal females of different ethnic cohorts residing in Auckland, New Zealand (NZ). METHODS: A total of 160 females aged 18-45 years participated in a cross-sectional study. Demographics, body composition, serum 25(OH)D, inflammatory markers (C-reactive protein and interleukin-6, IL-6), and iron biomarkers (serum ferritin, haemoglobin, soluble transferrin receptor, and hepcidin) were measured. Comparisons between parametric, non-parametric, and categorical variables were completed by using one-way ANOVA, Kruskal-Wallis, and Chi-squared tests, respectively. ANCOVA was used to compare serum 25(OH)D across iron parameter categories. RESULTS: Of the 160 participants, 60 were NZ European, 67 were South Asian, and 33 were from the 'other' ethnic groups. South Asians had significantly higher body fat percentage (BF%) 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 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 25(OH)D concentration was seen in those with lower (≤ 3.5 nM) hepcidin concentration, p = 0.0046. In South Asians, higher 25(OH)D concentration was seen in those with higher (> 3.5 nM) hepcidin concentrations, p = 0.038. There were no associations between serum 25(OH)D and serum ferritin. CONCLUSION: Within South Asian women, an unexpected positive relationship between 25(OH)D and hepcidin concentration was observed which may be due to significantly higher IL-6 concentrations, BF%, and lower 25(OH)D concentrations. Future research is required to confirm these observations in this ethnic cohort.

Iron deficiency and risk factors in pre-menopausal females living in Auckland, New Zealand.

BACKGROUND AND OBJECTIVES: Iron deficiency is prevalent in New Zealand, with low dietary haem intake and blood loss previously identified as risk factors. However, the influence of the hormone hepcidin on iron status has not been investigated. METHODS AND STUDY DESIGN: Females (n=170) aged 18-45 residing in Auckland participated in a cross-sectional study. Iron status and inflammation were assessed with serum biomarkers including; serum ferritin, haemoglobin, soluble transferrin receptor, hepcidin, C-reactive protein and interleukin-6. Lifestyle factors were assessed using a series of validated questionnaires, including an iron food frequency questionnaire. Potential determinants of serum ferritin were identified using multiple linear regression analysis. RESULTS: Iron insufficiency was confirmed in 55.8% of participants (Serum ferritin <30 µg·L-1). Hepcidin levels were higher in those who were iron sufficient (Serum ferritin ≥30 µg·L-1) (6.62 nM vs 1.17 nM, p<0.001). South Asian females had higher hepcidin (8.78 nM) levels, compared to New Zealand Europeans (6.28 nM) (p=0.018), a result likely due to South Asians presenting with higher interleukin-6 (1.66 vs 0.63 pg·mL-1, p<0.001). Hepcidin (ß=0.082, p<0.001) and frequency of meat intake (ß=0.058, p=0.001) were identified as significant predictors of serum ferritin in New Zealand Europeans, while hepcidin was the only identified predictor in South Asians (ß=0.138, p<0.001) and those of other ethnicities (ß=0.117, p<0.002). CONCLUSIONS: This is the first study in New Zealand to show that hepcidin levels strongly predict serum ferritin in premenopausal females. Additionally, frequency of meat intake appears to be an important determinant of iron status in New Zealand Europeans.