Diet quality and iron status among postpartum women living in Palmerston North, New Zealand : Mother and Infant Nutrition Investigation (MINI) study : a thesis presented in partial fulfilment of the requirements for the degree of Master of Science in Nutrition and Dietetics at Massey University, Auckland, New Zealand

Abstract

Background: Iron deficiency (ID) and anaemia are prevalent among postpartum women and represent an important public health concern. During the postpartum period, inadequate iron status can contribute to fatigue, impaired cognitive function and reduced quality of life, with potential consequences for both maternal and infant well-being. Despite the recognised importance of nutrition during this life stage, there is limited research on the relationship between overall diet quality and iron status among postpartum women in New Zealand (NZ). Objective: To investigate the relationship between diet quality and iron status in postpartum women in New Zealand. Methods: This secondary data analysis used the data collected from 87 postpartum women living in Palmerston North, New Zealand. Participants were recruited for the Mother and Infant Nutrition Infant Investigation (MINI) study. At six months postpartum 75 participants completed a weighed four-day food diary (4DDD) to assess dietary intake. Diet quality was calculated using a modified Dietary Guideline Index (DGI) adapted to New Zealand dietary guidelines. Iron status was assessed through serum ferritin (SF) and haemoglobin (Hb) biomarkers. C-reactive protein (CRP) was used to adjust for inflammation. Statistical analysis was conducted to find associations between diet quality, iron status, and sociodemographic factors. Nonparametric data were expressed as median and interquartile range (median [Q1, Q3]), while categorical variables were expressed as frequencies and percentages. Results: The median total dietary guideline index score (TDGIS) for postpartum women was 59.5/100 [54.1, 68.3]. Adherence to individual dietary components varied, with the highest adherence for protein (72% met recommendations) and the lowest for dairy (12%). Only 30.7% of participants met vegetable recommendations, 33.3% for fruit, and 22.7% for grains. The median diet variety score was 26 [23.0, 29.0] out of a possible 65, with participants achieving on average 43.6% of the highest possible variety score. Iron insufficiency (SF<30 μg/L) was confirmed in 12.9% (n=9) of participants. Participants with iron sufficiency had significantly higher total dietary guideline index scores (TDGIS) (60.9 [55.0, 69.1]) compared to iron-insufficient participants (53.6 [46.1, 61.4], p=0.026) out of 100. Grain intake was significantly higher in iron-sufficient participants (4.5 [3.9,5.8]) compared to iron-insufficient participants (3.2 [1.8,4.4], p=0.014). Higher education attainment was positively associated with iron sufficiency and higher total dietary guideline index scores (p<0.001). Conclusion: This is the first study in NZ to investigate the association between diet quality and iron status among the postpartum population in NZ, to the best of our knowledge. The findings of this study suggest that a lower diet quality is associated with an increased risk of insufficient iron levels. This finding reinforces the importance of postpartum nutrition. The positive relationship between diet quality and education highlights the role of community-based nutrition education to support postpartum women, with targeted public health interventions targeted for those at higher risk. Future research should continue to prioritise diet quality while incorporating distinctions between haem and non-haem iron sources and other dietary factors influencing iron absorption to further understand the relationship between diet and iron status in postpartum women.