Mother and Infant Nutrition Investigation - Investigating micronutrient intake and status in mothers and babies, and their possible effects on thyroid function

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The objective of this study is to investigate intake and status of micronutrients (iodine, selenium, and iron) and to explore effects on thyroid function and risk of postnatal depression in postpartum women and their infants, resident in the lower North Island of New Zealand. This follows two recent government initiatives - mandatory fortification of bread with iodised salt in September 2009; and the provision of an iodine supplement for all pregnant and lactating women from July 2011. The study aims are to analyse postpartum women’s iodine, selenium, iron intake and status, measure whether multiple micronutrient deficiencies may adversely affect thyroid function; assess whether postpartum women remain iodine deficient despite the two recent government initiatives; investigate to what extent inadequate status of iodine, selenium and iron are associated with the risk of postnatal depression in participating women, which, subsequently, may adversely affect their infant’s development. Iodine is an important trace element for both postpartum women and their infants; iodine deficiency has been described as the single greatest cause of preventable mental impairment. Coexisting inadequacy of iodine, selenium, and iron status has been suggested to impair optimal thyroid function. It is important to investigate the intakes and status of iodine, selenium, and iron together, rather than investigating a single micronutrient in isolation. We will recruit 250 postpartum women (at least 3 weeks to 3 months postpartum) of a range of ethnicities and socio-economic backgrounds, within the lower North island of New Zealand. Dietary assessment will be used to collect data about intake of selected micronutrients. Maternal health and child development through the first year of the life will be assessed by questionnaires. Biological samples (urine, breast milk and blood samples and nail clippings) will be collected to measure micronutrient status and thyroid function.