Contemporary challenges and opportunities for iodine nutrition

Bouga, Maria (2019) Contemporary challenges and opportunities for iodine nutrition. PhD thesis, University of Glasgow.

Abstract

Iodine deficiency has been a public health concern for many decades in countries of the developing world. Recently renewed concern was expressed in industrialised countries over mild insufficiency in high-risk groups of the population (pregnant and lactating women and their infants). The main sources of iodine in the UK diet are dairy, and fish and seafood products, while iodised salt is not widely available and does not contribute to iodine intake, contrary to most countries in Europe and globally. Iodine is essential for thyroid hormone synthesis, which are crucial for the neurodevelopment of the fetus and infant. Goiter is a visible symptom of severe iodine deficiency (ID), and consequences of ID during pregnancy vary from development of hypothyroidism to cretinism. Consequences of mild-to-moderate deficiency are less well described, with a reduction of IQ in children born to mothers with mild iodine deficiency. As such, pregnant women, lactating mothers and their infants are at risk of the irreversible consequences of low iodine intake. The World Health Organisation (WHO) recommends an iodine intake approximately 80% higher during pregnancy and lactation. The proposed strategy to combat ID worldwide has been universal salt iodisation. The UK has not implemented any prophylactic measures for ID and the female population in the perinatal period of life remain at risk, with up to 60% of women in pregnancy having insufficient iodine intake. The aim of this thesis was to explore the role that dietary guidance can play in tackling iodine insufficiency in women of childbearing age (pregnant and lactating) in the UK.

The MABY study (Chapter 2) examined the iodine intake of pregnant women in the UK and its association with mother’s (postpartum) and infant’s iodine status. This longitudinal study of 609 pregnant women in the 28th week of gestation showed that only 34% achieved the recommended daily iodine intake during pregnancy (recommendation 250 μg/day; median 199 μg/day; IQR 121-274). The iodine status of infants was sufficient, as measured in spot urine samples five days postpartum (median 118 μg/l; IQR 71–201). However, 41% of the group remained below the 100 μg/l cut-off point for sufficiency. Breastfed infants had 37% higher UIC compared to formula fed infants (p=0.002), although lactating mothers had 34% lower UIC compared to formula feeders (p=0.002), highlighting a potentially protective effect in newborns. Overall, iodine insufficiency in pregnant and lactating women in the UK remains an existing public health concern, which requires actions to address it.

To explore effective ways to eliminate iodine insufficiency using food and educational strategies, Chapter 3 presents a systematic review of the intervention studies that aimed to increase iodine-rich foods consumption (milk, fish, seaweed), with iodine status as an outcome. Only three studies were included in the review, one of which was a published protocol for an intervention. None of the studies reported improved iodine status. However, knowledge, attitude and practice scores (measured with a questionnaire) improved after an educational intervention in Iran. Chapter 3 confirmed a lack of intervention studies using dietary guidance, education, or provision of iodine-rich foods to increase iodine status, showing a gap in the literature.

Awareness and knowledge on iodine are low in women and healthcare professionals. Chapter 4 tested perceptions on dietary guidance related to iodine and pregnancy, using a mixed-methods design in 48 women. Participants in the perinatal period of life were unaware of the importance, sources and recommendations for iodine intake. Attitudes to dairy product consumption were positive, but increased fish consumption was considered less achievable. Barriers included taste, smell, heartburn and morning sickness in pregnancy. The main recognised provider of dietary advice were community midwives, although the dietary advice received focused most often on multivitamin supplements rather than food sources. Thematic analysis highlighted a clear theme of commitment to change behaviour, motivated by pregnancy, with a desired focus on user-friendly documentation.

Two cross-sectional questionnaire surveys, described in Chapters 5 and 6, investigated the perception, knowledge, awareness and practice towards dairy and seafood products in UK residents. The Theory of Planned Behaviour informed the design of the questionnaires. Less than two dairy servings per day were consumed by 46% of the population (median daily servings 2.2; IQR 1.2-3.5) and less than two fish and seafood servings per week were consumed by 53% (median daily servings 1.9; IQR 0.9-3.7). Knowledge, intentions and attitudes towards behaviour were higher both for “high” consumers (defined as those consuming >2 servings of dairy per day or >2 servings of fish per week). Main factors influencing the choice of these iodine-rich foods were the sensory attributes of the products, both as barriers and as facilitators of consumption, due to the variety and different characteristics of dairy and seafood products.

An intervention was designed based on the findings of Chapters 4, 5 and 6, to increase the iodine status of pregnant women and women trying to conceive. The PICk study, a single-blind randomised control trial was conducted in Glasgow, UK, and a feasibilityanalysis of the first 33 participants completed was performed. The educational intervention, based on regular text messages on iodine nutrition, was well-accepted by women. Burden was low, although dropout rates have been higher than those initially calculated (24% versus 15%). The study has been shown to be feasible and acceptable in these population groups. At the moment, the sample size limits interpretation of the interim findings, and further analysis after the completion of the study will indicate whether iodine status can be improved through the intervention.

It is important that iodine insufficiency should be tackled, to avoid the irreversible consequences on the population. To address iodine insufficiency effectively, solutions should be designed and work synergistically. Changing dietary patterns is challenging, but pregnancy offers the opportunity for implementation of changes, due to higher motivation and health consciousness. Increasing awareness and knowledge of the population, healthcare professionals and government organisations might be the key for future action. High quality and consistent results from research studies are needed to inform policy changes. This thesis identifies that knowledge and intentions of the population are important targets for public health interventions and offers suggestions on different approaches for the elimination of ID in the UK.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: iodine, nutrition, pregnancy, diet.
• Subjects: R Medicine > RA Public aspects of medicine; R Medicine > RA Public aspects of medicine > RA0421 Public health. Hygiene. Preventive Medicine
• Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Medicine, Dentistry & Nursing
• Funder's Name: Glasgow Children's Hospital Charity (GCHC)
• Supervisor's Name: Combet, Dr. Emilie and Lean, Prof. Michael E.J.
• Date of Award: 2019
• Embargo Date: 14 January 2022
• Depositing User: Miss Maria Bouga
• Unique ID: glathesis:2019-40924
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 23 Jan 2019 11:58
• Last Modified: 18 Apr 2024 12:27
• Thesis DOI: 10.5525/gla.thesis.40924
• URI: https://theses.gla.ac.uk/id/eprint/40924

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