Abstract
In response to the re-emergence of iodine deficiency in New Zealand, in 2009 the government mandated that all commercially made breads be fortified with iodized salt. There has been no evaluation of the impact of the program on iodine status of the elderly, despite this population group being vulnerable to iodine deficiency or excess. The aim of this study was to describe the iodine status of elderly New Zealanders in residential aged-care homes following the implementation of the bread fortification program. A cross-sectional survey was conducted, involving 309 residents (median age 85 years) from 16 aged-care homes throughout NZ. Information on socio-demographic, anthropometric, dietary and health characteristics were collected. Casual spot urine samples were analysed for urinary iodine concentration (UIC). Blood samples were analysed for serum thyroglobulin, thyroglobulin antibodies, and other biochemical indices. The median UIC (MUIC) of the residents was 72 μg/L, indicating mild iodine deficiency, and 29% had a UIC < 50 μg/L. Median thyroglobulin concentration was 18 ng/mL and 26% had elevated thyroglobulin concentration (>40 ng/mL), suggesting iodine insufficiency. Diuretic use was associated with lower MUIC (p = 0.043). Synthetic thyroxine use was associated with lower odds of having a UIC < 50 μg/L (OR 0.32, p = 0.030)) and lower median thyroglobulin (−15.2 ng/mL, p = 0.001), compared with untreated participants. Frailty was associated with elevated thyroglobulin (p = 0.029), whereas anemia was associated with lower thyroglobulin (p = 0.016). Iodine insufficiency persists in New Zealanders residing in residential aged-care homes despite increasing iodine intake from fortified bread. Research is required to establish optimal iodine intake and status in the elderly.
Highlights
Iodine is an essential component of thyroid hormones, which are required for maintenance of tissues and regulation of the metabolic rate
The findings from our nation-wide survey indicate that despite the implementation of mandatory fortification of commercially baked bread with iodized salt in late 2009, iodine insufficiency persists in this elderly population group residing in long-term residential care
Participants were classified as mildly iodine deficient, based on internationally recognized criteria recommend by the WHO/UNICEF/ICCIDD for assessing population iodine adequacy with urinary iodine concentration (MUIC between 100 and 199 μg/L, with no more than 20% of samples below μg/L [24])
Summary
Iodine is an essential component of thyroid hormones, which are required for maintenance of tissues and regulation of the metabolic rate. Inadequate iodine intake can lead to thyroid dysfunction, which in turn causes a range of adverse health conditions collectively referred to as Iodine Deficiency. Thyroid dysfunction in adults is associated with a number of important adverse health outcomes, including hypertension, dyslipidemia, cognitive impairment, osteoporosis, muscle wasting, frailty, and neuromuscular dysfunction [3]. Older adults are at increased susceptibility to iodine deficiency or Nutrients 2016, 8, 445; doi:10.3390/nu8080445 www.mdpi.com/journal/nutrients. Thyroid autonomous nodules are increased in older adults who reside in areas of mild to moderate iodine deficiency, and are associated with subclinical hyperthyroidism when iodine intake is low, or after increases in intake following implementation of iodine fortification programs [2]
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