Vegan and vegetarian diets are widely supported and adopted, but individuals following such diets remain at greater risk of iodine deficiency. This systematic review and meta-analysis was conducted to assess the iodine intake and status in adults following a vegan or vegetarian diet in the modern day. A systematic review and quality assessment were conducted from October 2020 to December 2022 according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) and Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidance. Studies were identified in Ovid MEDLINE, Web of Science, PubMed, and Scopus. Eleven articles were eligible for review containing 4421 adults (aged ≥ 18 years). Vegan groups had the lowest median urinary iodine concentration (mUIC) (12·2/l). None of the dietary groups had mUIC within the optimal range for iodine status (100–200 µg/l) (WHO). Vegan diets had the poorest iodine intake (17·3 µg/d) and were strongly associated with lower iodine intake (P = < 0·001) compared with omnivorous diets. Lower intake in vegan diets was influenced by sex (P = 0·007), the presence of voluntary or absence of Universal Salt Iodisation (USI) programmes (P = 0·01 & P = < 0·001), and living in a country with adequate iodine nutrition (P = < 0·001). Vegetarians and particularly vegans living in countries with no current USI programme continue to have increased risk of low iodine status, iodine deficiency and inadequate iodine intake. Further research into the usefulness of mandatory fortification of vegan appropriate foods is required.

Iodine supply is crucial during pregnancy to ensure that the proper thyroid function of mother and baby support fetal brain development. Little is known about iodine status or its dietary determinants in pregnant women in the Republic of Cyprus. We therefore recruited 128 pregnant women at their first-trimester ultrasound scan to a cross-sectional study. We collected spot-urine samples for the measurement of urinary iodine concentration (UIC, µg/l) and creatinine concentration (Creat, g/l), the latter of which allows us to correct for urine dilution and to compute the iodine-to-creatinine ratio (UI/Creat). Women completed a FFQ and a general questionnaire. We used a General Linear model to explore associations between maternal and dietary characteristics with UI/Creat. The median UIC (105 µg/l) indicated iodine deficiency according to the WHO criterion (threshold for adequacy = 150 µg/l), and the UI/Creat was also low at 107 µg/g. Only 32 % (n 45) of women reported the use of iodine-containing supplements; users had a higher UI/Creat than non-users (131 µg/g v. 118 µg/g), though this difference was NS in the adjusted analysis (P = 0·37). Of the dietary components, only egg intake was significantly associated with a higher UI/Creat in adjusted analyses (P = 0·018); there was no significant association with milk, dairy products or fish intake. Our results suggest that pregnant women in Cyprus have inadequate iodine status and are at risk of mild-to-moderate iodine deficiency. Further research on dietary sources in this population is required.

Iodine intake and excretion vary widely; however, these variations remain a large source of geometric uncertainty. The present study aims to analyse variations in iodine intake and excretion and provide implications for sampling in studies of individuals or populations. Twenty-four healthy women volunteers were recruited for a 12-d sampling period during the 4-week experiment. The duplicate-portion technique was used to measure iodine intake, while 24-h urine was collected to estimate iodine excretion. The mean intra-individual variations in iodine intake, 24-h UIE (24-h urinary iodine excretion) and 24-h UIC (24-h urinary iodine concentration) were 63, 48 and 55 %, respectively, while the inter-individual variations for these parameters were 14, 24 and 32 %, respectively. For 95 % confidence, approximately 500 diet samples or 24-h urine samples should be taken from an individual to estimate their iodine intake or iodine status at a precision range of ±5%. Obtaining a precision range of ±5% in a population would require twenty-five diet samples or 150 24-h urine samples. The intra-individual variations in iodine intake and excretion were higher than the inter-individual variations, which indicates the need for more samples in a study on individual participants.

I prophylaxis is the most effective strategy to eradicate I deficiency disorders, but it has been shown to affect the thyroid disease pattern. In this study, we assessed the frequency of thyroid disorders in an adult population living in two areas of southern Italy after implementing I prophylaxis. To this aim, a cross-sectional, population-based study including 489 subjects from an I-deficient rural and an I-sufficient urban area of southern Italy was conducted. Thyroid ultrasound was performed on all participants, and urine and blood samples were collected from each subject. The levels of thyroid-stimulating hormone (TSH), thyroglobulin (TgAb) and thyroperoxidase antibodies (TPOAb), urinary I excretion (UIE), and thyroid volume and echogenicity were evaluated. We found that the median UIE was higher in the urban than in the rural area (P=0·004), whereas the prevalence of subjects affected by goitre was higher in the rural compared with the urban area (P=0·003). Positive TgAb rather than TPOAb were more frequent in subjects from the urban area compared with the rural area (P=0·009). The hypoechoic pattern at thyroid ultrasound (HT-US) was similar between the two areas, but TgAb were significantly higher (P=0·01) in HT-US subjects from the urban area. The frequency of elevated TSH did not differ between the two screened populations, and no changes were found for TgAb positivity in subjects with high TSH in the urban compared with the rural area. Our findings support that the small risks of I supplementation are far outweighed by the substantial benefits of correcting I deficiency, although continued monitoring of populations is necessary.

Iodine deficiency is still common in some European countries. In Denmark an iodine fortification programme was introduced in 1998 and a monitoring programme was established prior to iodization. This study reports the change in urinary iodine excretion caused by fortification and investigates determinants of iodine intake after fortification. Iodine excretion in casual urine samples was assessed in 4649 subjects in 1997–8 and in 3570 comparable subjects in 2004–5 in women 18–22, 25–30, 40–45 and 60–65 years of age and in men 60–65 years of age living in Aalborg (western part of Denmark) or Copenhagen (eastern part of Denmark). These areas had moderate and mild iodine deficiency, respectively, before iodine fortification. All subjects filled in a FFQ and a questionnaire regarding lifestyle factors. Iodine excretion, expressed as the estimated 24 h urinary iodine excretion and as urinary iodine concentration, increased significantly in all age and sex groups. However, the iodine intake was still below the recommended in the youngest age groups in both cities and in women 40–45 years of age living in Aalborg. Intake of milk and salt had strong significant direct associations with iodine excretion (P < 0·001). It is concluded that although the median iodine intake in the whole study population is at the recommended level, some groups still have an intake below the recommended. It is important to have a moderate milk intake to obtain a sufficient iodine intake in Denmark.

Iodine deficiency disorders (IDD) are related to the degree of iodine deficiency. In european countries, characterized by mild to moderate iodine deficiency, neurological deficits or minor neuropsychological impairments have been described. Urinary iodine excretion (UIE) ranged from 30 to 170 mcg/L, 141 millions of people were at risk of IDD, 97 millions were affected by goiter and 0.9 millions had an impaired mental development.

Iodine prophylaxis is devoid of adverse reactions with the exception of sporadic cases of transitory hyperthyroidism, associated to the severity of iodine deficiency before the prophylaxis. The International Council for Control of IDD recommends an universal iodine prophylaxis, instituted gradually in severe iodine deficient countries. The total cost of universal iodine prophylaxis is very cheap compared to the social cost of goiter and cretinism.

In conclusion, most european countries are still characterized by mild to moderate iodine deficiency. Iodine prophylaxis programs are already operating, its cost is irrelevant with respect to the undebatable beneficial impact on the health. Adverse effects are not observed except in severe iodine deficient areas where iodine intake was abruptly increased.

I deficiency diseases remain a health problem even in some developed countries. Therefore, measurement of I intake and knowledge about food choice related to I intake is important. We examined I intake in 4649 randomly selected participants from two cities in Denmark (Copenhagen and Aalborg) with an expected difference in I intake. I intake was assessed both by a food frequency questionnaire and by measuring I in casual urine samples. I excretion was expressed as a concentration and as estimated 24-h I excretion. Further, subgroups with low I intake were recognized. I intake was lower in Aalborg than in Copenhagen for all expressions, and lower than recommended in both cities if I intake from supplements was not included. Milk was the most important I source, accounting for about 44 % of the I intake, and milk (P<0·001) and fish (P=0·009) intake was related to I excretion in a multiple linear regression model. Thus, risk groups for low I intake were individuals with a low milk intake, those with a low intake of fish and milk, those not taking I supplements and those living in Aalborg where the I content in drinking water is lower. Even individuals who followed the advice regarding intake of 200–300 g fish/week and 0·5 litres milk/d had an intake below the recommended level if living in Aalborg.