Iodine is essential for thyroid hormone synthesis. Individuals adhering to vegan and vegetarian diets have been found to be vulnerable to iodine deficiency. Yet, iodine has not been monitored in these groups across time. This study aims to investigate iodine status, intake and knowledge in vegans, vegetarians, and omnivores and determine changes between 2016-17 and 2019.
Dietary intake (µg day−1) was estimated by three-day food diaries (FD), and iodine food frequency questionnaires (FFQ). Urinary iodine concentration (UIC), analysed by ICP-MS, assessed iodine status according to World Health Organisation (WHO) criteria. Iodine knowledge was scored by an adapted questionnaire. IBM SPSS was used for statistical analysis.
Ninety-six adults (18-60 y) were recruited in October 2016-17 (vegans; 12, vegetarians; 5, omnivores; 43) and June 2019 (vegans; 7, vegetarians; 10, omnivores; 19). Median dietary iodine was below the Reference Nutrient Intake (RNI) for all groups. Vegans and vegetarians had the lowest iodine intake. Vegans had significantly lower iodine intake than omnivores (2016-17; P = 0.032, 2019; P = 0.001). Omnivores had the highest iodine status (2016-17; 79.4 µg L−1, 2019; 72.4 µg L−1), and vegans the lowest (2016-17; 31.2 µg L−1, 2019; 12.2 µg L−1). Iodine knowledge was poor, but did not differ between dietary groups (2016-17; P = 0.219, 2019; P = 0.532).
Vegans and vegetarians continue to be at risk of iodine deficiency. Further, iodine intake in the UK is poor independent of dietary choice. Iodine education is needed along with, research into improving iodine nutrition at national level.