Restricted diets, micronutrient intake, and nutritional status

Eveleigh, Elizabeth (2023) Restricted diets, micronutrient intake, and nutritional status. PhD thesis, University of Nottingham.

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Iodine deficiency in the UK has re-emerged in vulnerable groups. Dietary iodine has an essential role in the formation of thyroid hormones which regulate growth and metabolism. Iodine deficiency is particularly problematic for women of childbearing age and those who are pregnant and/or lactating as optimal thyroid function is vital for foetal neurodevelopment. Today, iodine deficiency is still considered the biggest single preventable cause of brain damage globally (WHO, 2007).

Vegans and vegetarians have been identified as a sub-group with an increased risk of iodine deficiency due to restricting foods that are typically known for being iodine rich (e.g. cow’s milk, dairy products, white fish, and eggs). The risk of iodine deficiency is particularly problematic in vegan and vegetarian populations due to the uptake of these diets in young women. Globally, we are experiencing a transition to more sustainable diets and likely, the proportion of the world’s population adhering to vegan/vegetarian diets will increase in the next decade. However, there are still few studies addressing iodine nutrition in individuals following vegan and vegetarian diets.

The research offered within this thesis aimed to investigate and expand the field of iodine in vegan and vegetarian diets. To do this, we addressed: (i) the world’s literature on the topic of iodine in vegan and vegetarian diets; (ii) the prevalence of low iodine intake, status, and knowledge of habitual vegans and vegetarians living in an area historically associated with iodine deficiency (Nottinghamshire); (ii) the influence of short-term (4-week) vegan diets on iodine and micronutrient intake, and status; (iv) approaches to improve the iodine nutrition of individuals following vegan diets.

The first research article systematically reviewed 15 studies exploring the iodine intake and status of individuals following vegan and vegetarian diets residing in industrialised countries. Vegans were found to have an increased risk of low iodine status, deficiency, and inadequate intake compared with adults following less restrictive diets. This article also found that the level of iodine deficiency in vegans appears to relate closely to national iodine status.

The second research project (a cross-sectional study of iodine nutrition in Nottinghamshire) determined that although vegans and vegetarians had the lowest iodine intake and status compared to omnivores, median dietary iodine was below the Reference Nutrient Intake (RNI) for all groups. We also discuss that iodine knowledge is very poor among British participants. The third study identified that following a short-term vegan diet as part of global campaigns such as ‘Veganuary’ significantly reduced the iodine and B12 intake of omnivorous participants. However, long-term markers of iodine status and thyroid function did not change, suggesting that the endocrine systems can adapt to some extent to a temporary decline in dietary iodine. The fourth study proposes a clinical trial protocol to address the effectiveness of iodine-fortified alternative milk as a vehicle to improve iodine intake in vegans. Our final study re-evaluates the literature in the field of iodine in vegan and vegetarian diets. Results from our meta-analysis suggest that vegans are significantly more likely to have low iodine intake compared to omnivores. We also identify that voluntary salt fortification schemes may overlook vegan and vegetarian individuals within the population. The research presented in this thesis confirms that vegans and vegetarians are a sub-group with an increased risk of iodine deficiency. Our findings could have devastating public health consequences given that these diets are frequented by women of childbearing age. We also confirm that iodine deficiency is re-emerging in the UK. There is an urgent need to implement national strategies and policies to improve iodine awareness and promote the consumption of appropriate iodine sources for all dietary groups. Continued monitoring of individuals following vegan and vegetarian diets is required as more individuals transition to sustainable diets globally.

Item Type: Thesis (University of Nottingham only) (PhD)
Supervisors: Welham, S.J.
Coneyworth, L.
Keywords: Micronutrients, iodine, iodine deficiency, vegan, vegetarian, deficiency, plant-based, nutrition, dietary intake
Subjects: R Medicine > RA Public aspects of medicine > RA 421 Public health. Hygiene. Preventive Medicine
R Medicine > RM Therapeutics. Pharmacology
Faculties/Schools: UK Campuses > Faculty of Science > School of Biosciences
Item ID: 76236
Depositing User: Eveleigh, Elizabeth
Date Deposited: 21 Dec 2023 10:46
Last Modified: 21 Dec 2023 10:46

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